Birth

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UNSW Embryology is educational resource for learning concepts in embryological development, no clinical information is provided and content should not be used for any other purpose.


Introduction

Newborn infant
Birth by caesarean

Birth or parturition is a critical stage in development, representing in mammals a transition from direct maternal support of fetal development, physical expulsion and establishment of the newborns own respiratory, circulatory and digestive systems. These notes only cover the biological processes surrounding birth including fetal signaling changes and maternal signaling changes. Note that there is a growing worldwide trend in developed countries toward caesarean section delivery. There are a great number of comprehensive, scientific and general, books and articles that cover birth, childbirth or parturition. The time surrounding birth is known as the perinatal period.


More than 136 million women give birth a year, 16 million are girls aged between 15 and 19. (WHO)



Birth Links: Introduction | Lecture - Birth | Caesarean | Preterm | Birth Weight | Birth Statistics | Australian Birth Data | Developmental Origins of Health and Disease | Macrosomia | Neonatal Diagnosis | Apgar test | Guthrie test | Neonatal Development | Stillbirth and Perinatal Death | ICD-10 Perinatal Period | Category:Birth

Some Recent Findings

  • American College of Obstetricians and Gynecologists Committee opinion no 579: definition of term pregnancy.[1] "In the past, the period from 3 weeks before until 2 weeks after the estimated date of delivery was considered "term," with the expectation that neonatal outcomes from deliveries in this interval were uniform and good. Increasingly, however, research has shown that neonatal outcomes, especially respiratory morbidity, vary depending on the timing of delivery within this 5-week gestational age range. To address this lack of uniformity, a work group was convened in late 2012, which recommended that the label "term" be replaced with the designations early term (37 0/7 weeks of gestation through 38 6/7 weeks of gestation), full term (39 0/7 weeks of gestation through 40 6/7 weeks of gestation), late term (41 0/7 weeks of gestation through 41 6/7 weeks of gestation), and postterm (42 0/7 weeks of gestation and beyond) to more accurately describe deliveries occurring at or beyond 37 0/7 weeks of gestation."
  • Do parental heights influence pregnancy length?[2] "Parents who participated in the Nord-Trøndelag Health Study (HUNT 2; 1995-1997) were linked to offspring data from the Medical Birth Registry of Norway (1997-2005). The main analyses included 3497 women who had delivered 5010 children, and 2005 men who had fathered 2798 pregnancies. ...Women with shorter stature had shorter pregnancy length and lower risk of post-term births than taller women, and when EDD was based on ultrasound, they also had higher risk of preterm births. The effect of maternal height was generally stronger when pregnancy length was based on second trimester ultrasound compared to last menstrual period. The association of maternal height with pregnancy length could not be explained by cardiovascular risk factors. Paternal height was neither associated with pregnancy length nor with the risk of pre- and post-term birth."
  • Global and Regional Differences in Brain Anatomy of Young Children Born Small for Gestational Age (SGA)[3] "Children born SGA displayed reduced cerebral and cerebellar grey and white matter volumes, smaller volumes of subcortical structures and reduced cortical surface area. Regional differences in prefrontal cortical thickness suggest a different development of the cerebral cortex. SGA children with bodily catch-up growth constitute an intermediate between those children without catch-up growth and healthy controls. Therefore, bodily catch-up growth in children born SGA does not implicate full catch-up growth of the brain."
  • Does Birth Weight Influence Physical Activity in Youth? A Combined Analysis of Four Studies Using Objectively Measured Physical Activity[4] "Overall this combined analysis suggests that birth weight is not an important biological determinant of habitual physical activity or sedentary behaviour in children and adolescents. This reassuring finding suggests that although lower birth weight may reduce physical capacity in later life, this does not extend to reducing levels of habitual physical activity."
  • Are babies getting bigger? An analysis of birthweight trends in New South Wales, 1990-2005.[5] "The proportion of babies born LGA increased from 9.2% to 10.8% (18% increase) for male infants and from 9.1% to 11.0% (21% increase) for female infants. The mean birthweight increased by 23 g for boys and 25 g for girls over the study period. Increasing maternal age, higher rates of gestational diabetes and a decline in smoking contributed significantly to these increases, but did not fully explain them."
More recent papers
Mark Hill.jpg
This table shows an automated computer PubMed search using the listed sub-heading term.
  • Therefore the list of references do not reflect any editorial selection of material based on content or relevance.
  • References appear in this list based upon the date of the actual page viewing.

References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.

Links: References | Discussion Page | Pubmed Most Recent


Search term: Birth

P Perimenis, T Bouckenooghe, J Delplanque, E Moitrot, E Eury, S Lobbens, P Gosset, L Devisme, B Duvillie, A Abderrahmani, L Storme, P Fontaine, P Froguel, A Vambergue Placental antiangiogenic prolactin fragments are increased in human and rat maternal diabetes. Biochim. Biophys. Acta: 2014; PMID:24984282 Marianne T Neary, Keat-Eng Ng, Marthe H R Ludtmann, Andrew R Hall, Izabela Piotrowska, Sang-Bing Ong, Derek J Hausenloy, Timothy J Mohun, Andrey Y Abramov, Ross A Breckenridge Hypoxia signaling controls postnatal changes in cardiac mitochondrial morphology and function. J. Mol. Cell. Cardiol.: 2014; PMID:24984146 Elaine Reese, Tia Neha Let's kōrero (talk): The practice and functions of reminiscing among mothers and children in Māori families. Memory: 2014;1-12 PMID:24984106 Neeraj Narula, Raed Al-Dabbagh, Amit Dhillon, Bruce E Sands, John K Marshall Anti-TNFα Therapies Are Safe During Pregnancy in Women with Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis. Inflamm. Bowel Dis.: 2014; PMID:24983985 Sinéad M O'Neill, Esben Agerbo, Louise C Kenny, Tine B Henriksen, Patricia M Kearney, Richard A Greene, Preben Bo Mortensen, Ali S Khashan Cesarean Section and Rate of Subsequent Stillbirth, Miscarriage, and Ectopic Pregnancy: A Danish Register-Based Cohort Study. PLoS Med.: 2014, 11(7);e1001670 PMID:24983970

Search term: Childbirth

Sari Räisänen, Michael R Kramer, Mika Gissler, Juho Saari, Tuovi Hakulinen-Viitanen, Seppo Heinonen Smoking during pregnancy was up to 70% more common in the most deprived municipalities - A multilevel analysis of all singleton births during 2005-2010 in Finland. Prev Med: 2014; PMID:24983887 Jamie Winderbaum Fernandez, J Alex Grizzell, Rex M Philpot, Lynn Wecker Postpartum depression in rats: differences in swim test immobility, sucrose preference and nurturing behaviors. Behav. Brain Res.: 2014; PMID:24983658 Oluwarotimi Ireti Akinola, Adetokunbo O Fabamwo, Adetokunbo O Tayo, Kabiru A Rabiu, Oshodi Y Abisowo, Mercy E Alokha Caesarean section - an appraisal of some predictive factors in Lagos Nigeria. BMC Pregnancy Childbirth: 2014, 14(1);217 PMID:24981086 Madelynne A Arden, Alexandra Ms Duxbury, Hora Soltani Responses to gestational weight management guidance: a thematic analysis of comments made by women in online parenting forums. BMC Pregnancy Childbirth: 2014, 14(1);216 PMID:24981024 Carol A Aschenbrenner, Timothy T Houle, Silvia Gutierrez, James C Eisenach Modeling Individual Recovery after Peripheral Nerve Injury in Rats and the Effects of Parturition. Anesthesiology: 2014; PMID:24979387

Textbooks

  • Human Embryology (2nd ed.) Larson Chapter 15 pp471-488
  • The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapter 7 pp129-167

History

1770 2010
Historic model of birth

Teaching model of birth.

Birth- Magnetic Resonance Imaging 02.jpg

Magnetic Resonance Imaging of birth.

Birth MRI icon.jpg
 ‎‎Human Birth MRI
Page | Play

Gestation Period

Gestational Age GA

The American College of Obstetricians and Gynecologists Committee recently (2013) gave an opinion (no 579) definition of "term pregnancy".[1]

"In the past, the period from 3 weeks before until 2 weeks after the estimated date of delivery was considered "term," with the expectation that neonatal outcomes from deliveries in this interval were uniform and good. Increasingly, however, research has shown that neonatal outcomes, especially respiratory morbidity, vary depending on the timing of delivery within this 5-week gestational age range. To address this lack of uniformity, a work group was convened in late 2012, which recommended that the label "term" be replaced with the designations early term (37 0/7 weeks of gestation through 38 6/7 weeks of gestation), full term (39 0/7 weeks of gestation through 40 6/7 weeks of gestation), late term (41 0/7 weeks of gestation through 41 6/7 weeks of gestation), and postterm (42 0/7 weeks of gestation and beyond) to more accurately describe deliveries occurring at or beyond 37 0/7 weeks of gestation. The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine endorse and encourage the uniform use of the work group's recommended"


The American Academy of Pediatrics Committee on Fetus and Newborn (2004) issued a policy statement "Age Terminology During the Perinatal Period" [6]

"Gestational age GA (completed weeks): time elapsed between the first day of the last menstrual period and the day of delivery. If pregnancy was achieved using assisted reproductive technology, gestational age is calculated by adding 2 weeks to the conceptional age."

History

Historically, Franz Carl Naegele (1777-1851) developed the first scientific rule for estimating length of a pregnany. The median duration of gestation for first births from assumed ovulation to delivery was 274 days (just over 39 weeks). For multiple births, the median duration of pregnancy was 269 days (38.4 weeks).

"...one should count back 3 months from the first day of the last menses, then add 15 days for primiparas or 10 days for multiparas, instead of using the common algorithm for Naegele's rule."[7]

Last Menstrual Period

The Last Menstrual Period (LMP), the menstrual period (menses) that occurs before a pregnancy, has been widely used clinically as a date to calculate clinical pregnancy development (GA, gestational age). Note that in humans this is approximately two weeks different from embryonic development, which begins at fertilisation around the mid-point of the menstrual cycle.

The interval between the beginning of the LMP and fertilisation can have a wide range (7 to 25 days). This variation can be due to both maternal (menstrual cycle timing and ovulation) and fetal (blastocyst implantation) effects. The calculation also requires an accurate maternal recall of LMP and can be affected by irregular menses, first-trimester vaginal bleeding, unrecognized spontaneous abortions, oral contraceptive use.

Ultrasound

Measurement of fetal size by ultrasound has been used more recently to accurately calculate pregnancy development. The ultrasound measurement tends to be more accurate in early development staging, by the third trimester there can be some individual variations in fetal growth and the effects of abnormalities or fetal growth restriction. Serial ultrasound measurements may identify these abnormal growth effects.

Birth Statistics

USA Live Births and Fertility Rates

2007 Data [8] Number of births: 4,317,119 Birth rate: 14.3 per 1,000 population Fertility rate: 69.5 births per 1000 women aged 15-44 years Percent born low birthweight: 8.2% Percent unmarried: 39.7%

Australian Data

Australian-births 2007.png

UK Data

File-Scotland - spontaneous births 1980-2004.jpg
Scotland - Spontaneous births per 100,000 women of reproductive age, 1980–2004.[9]

Childbirth

Birth Stage 2
  • Parturition (Latin, parturitio = "childbirth") describes expelling the fetus, placenta and fetal membranes and is probably initiated by fetus not mother.
  • Preterm birth - Risks of preterm birth in abnormal low birth weight (intrauterine growth restriction) and high (large for gestational age) categories are 2- to 3-fold greater than the risk among appropriate-for-gestational-age infants.
  • Maternal labor - uterine contractions and dilation of cervix, process under endocrine regulation
  • Placenta and fetal membranes - (Latin, secundina = "following") expelled after neonate birth

Uterine Myometrial Changes

Human uterus normal and abnormal contractile activity[10]
  • Smooth muscle fibers - hypertrophy not proliferation
  • Stretching of myometrium - stimulates spontaneous muscular contraction, during pregnancy progesterone inhibits contraction
  • Stimulating contraction - increased estrogen levels (placental secretion sensitizes smooth muscle), increased oxytocin levels (fetal oxytocin release- force and frequency of contraction), fetal pituitary prostaglandin production (estrogen and oxytocin stimulate endometrial production of prostaglandin)
Hormones Roles
Progesterone
  • maintains pregnancy - initially synthesized by corpus luteum, then levels maintained by placenta
  • hyperpolarizes myometrial cells (-65 mV), reduces excitability and conductivity
  • Level in plasma may fall just before parturition, definitely decreases following delivery of placenta
Estrogens
  • Group of steroidal hormones, peak when parturition begins
  • induce increased synthesis of actomyosin and ATP in myometrial cells
  • alter membrane potential (-50 Mv) enhances excitation/conduction
  • act to directly increase myometrial contraction
  • indirectly by increasing oxytocin from pituitary gland
  • Estriol - synthesized by fetus and placenta
Oxytocin
  • Peptide hormone (8aa) from maternal posterior pituitary, initiation and maintenance of labour (synthetic form labour induction)
  • myometrium sensitivity to oxytocin (increased by estrogen, decreased by progesterone)
  • stimulus for release - mechanical stimulation of uterus, cervix and vagina (ethanol inhibits release)
Prostaglandins
  • hydroxy fatty acids - sythesized by placenta, amniotic fliud contains mainly PGF2 alpha, causes myometrial contraction (also in maternal plasma)
  • prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E2 (PGE2) - used to induce labour (intravenous, oral, intravaginal, intraamniotic)
  • Aspirin inhibitor of PG synthesis - leads to increased duration of pregnancy
Endocrine Birth

External Environment

  • mainly shown in other species parturition occurs in peaceful undisturbed surroundings, stress may have an inhibitory effect on oxytocin release
  • Most human births occur at night (peak at 3am) diurnal rhythm influence

Labor Stages

Cervical mucus plug
Birth Stage 2
Labour Stages Changes Time Roles
Stage 1 Dilatation 7 to 12 hours
longer for first child
Uterine contractions 10 minutes apart, function to dilate cervix fetal membranes rupture releasing amnion.
Stage 2 Expulsion 20 to 50 minutes Uterine contractions 2 to 3 minutes apart, function to push fetus through cervix and vagina.
Stage 3 Placental 15 minutes Uterine contractions following child delivery expel placenta. Haematoma separates placenta from uterine wall, separation occurs at spongy layer of decidua basalis.
Stage 4 Recovery 2+ hours Uterine contractions continue and myometrial contraction closes spiral arteries, also begins to reduce uterine volume.

Historic Birth Models

About The Models - a series of models commissioned by Giuseppe Galletti (? - 1819) currently held in the Institute and Museum of the History of Science (Italy) Istituto e Museo di Storia della Scienza (IMSS). Giuseppe Galletti and others used terracotta and wax models that he had commissioned in Florence between 1770 and 1775 to train surgeons and midwives.

About The Models - One of a series of models commissioned by Giuseppe Galletti (? - 1819) currently held in the Institute and Museum of the History of Science (Italy) Istituto e Museo di Storia della Scienza (IMSS). Giuseppe Galletti and others used terracotta and wax models that he had commissioned in Florence between 1770 and 1775 to train surgeons and midwives. Wax models are life-sized and the terracotta versions are reduced to a 1:3 scale.


Galletti models: Birth | Week 10 Fetus Model | Week 16 Fetus Model | Week 24 Fetus Model | Stage 1 Terracotta Model 1 | Stage 2 Terracotta Model 2 | Stage 1 Wax Model | Breech Birth 1 | Breech Birth 2 | Breech Birth 3 | Breech Birth Wax Model | Placenta Previa | Category:Galletti1770 | 17th and 18th Century Anatomies | Embryology History | Embryology Models

Image Source: Institute and Museum of the History of Science http://brunelleschi.imss.fi.it/museum/esim.asp?c=500156 Thanks to Sabina Bernacchini from Institute and Museum of the History of Science (Italy) IMSS for allowing reproduction of selected images from the Surgery and Obstetrics exhibition on this embryology education site.

Birth Weights

File:Brain growth and birth size

The primary causes of VLBW are premature birth (born <37 weeks gestation, and often <30 weeks) and intrauterine growth restriction (IUGR), usually due to problems with placenta, maternal health, or to birth defects. Many VLBW babies with IUGR are preterm and thus are both physically small and physiologically immature.


Birth weight (grams) less 500 500 – 999 1,000 – 1,499 1,500 – 1,999 2,000 – 2,499 2,500 – 2,999 3,000 – 3,499 3,500 – 3,999 4,000 – 4,499 4,500 – 4,999 5,000 or more
Classification Extremely Low Birth Weight Very Low Birth Weight Low Birth Weight Normal Birth Weight High Birth Weight

Weight Conversions

Extremely Low Birth Weight

  • Less than 500 grams (1 lb 1 oz or less)
  • 500 – 999 grams (1 lb 2 oz – 2 lb 3 oz)

Very Low Birth Weight

  • 1,000 – 1,499 grams (2 lb 4 oz – 3 lb 4 oz)

Low Birth Weight

  • 1,500–1,999 grams (3 lb 5 oz – 4 lb 6 oz)
  • 2,000–2,499 grams (4 lb 7 oz – 5 lb 8 oz)

Normal Birth Weight

  • 2,500–2,999 grams (5 lb 9 oz – 6 lb 9 oz)
  • 3,000–3,499 grams (6 lb 10 oz – 7 lb 11 oz)
  • 3,500–3,999 grams (7 lb 12 oz – 8 lb 13 oz)

High Birth Weight (macrosomia)

  • 4,000–4,499 grams (8 lb 14 oz – 9 lb 14 oz)
  • 4,500–4,999 grams (9 lb 15 oz – 11 lb 0 oz)
  • 5,000 grams or more (11 lb 1 oz or more)


Links: Birth-Weight | Fetal Origins Hypothesis | Maternal Diabetes

Newborn Homoeostasis

Brown adipose tissue

Newborn has to establish new functioning systems in a balanced and regulated manner (homoeostasis).

  • lung function
  • circulatory changes
  • thermoregulation
  • endocrine function
  • nutrition
  • gastrointestinal tract function
  • waste
  • kidney function


Glucocorticoids - have an important role in the preparation for birth, including involvement in lung and cardiac development, and the maturation of enzymes in a variety of pathways.

Respiration

Neonatal rib orientation
  • Lungs at birth collapsed and fluid-filled - replaced with air by powerful inspiratory movement and absorption through the alveoli
  • Lung epithelia has to rapidly change from its prenatal secretory function to that of fluid absorbtion.
    • initiated by a late fetal change in alveolar epithelial cell (AEC) chloride and fluid secretion to sodium and fluid absorption.
    • absorption requires sodium-potassium ATPase (Na-K-ATPase) together with apical sodium entry mechanisms (Epithelial Sodium Channels, ENaC)
    • Fetal thyroid hormone is thought to have a hormonal role in this developmental switch
  • These changes and pressure also lead to the pulmonary sytem becoming activated and changes in the circulatory shunting that existed before birth.
  • During the late fetal period regular fetal breathing movements (FBM) also occur preparing both the skeletomuscular sysyem and lungs mechanically for respiration.
  • Respiratory Rate is higher than adult (30 breaths/minute).
  • Rib Orientation - Infant rib is virtually horizontal, allowing diaphragmatic breathing only. Adult rib orientation is oblique (both anterior and lateral views), allows for pump-handle and bucket handle types of inspiration.


Links: Respiratory System Development

The First Breath

The exchange of lung fluid for air leads to:

  1. fall in pulmonary vascular resistance
  2. increase in pulmonary blood flow
  3. thinning of pulmonary arteries (stretching as lungs increase in size)
  4. blood fills the alveolar capillaries
  5. In the heart, pressure in the right side of the heart decreases and pressure in the left side of the heart increases (more blood returning from pulmonary).

See also the review; Clearance of lung liquid during the perinatal period[11] "At birth, the distal lung epithelium undergoes a profound phenotypic switch from secretion to absorption in the course of adaptation to air breathing."

Cardiovascular

  • Umbilical Vasculature - The umbilical blood vessel cavity is lost postnatally over the course of weeks to months after birth. The adult anatomical remnant of the umbilical vein between the umbilicus and liver is the ligamentum teres.
  • Foramen Ovale - two separate forms of foramen ovale closure; functional and structural. Functional closure begins at the first breath and is rapid. Structural (anatomical) closure is much slower and generally occurs before the end of the first year.
  • Ductus Arteriosus - a direct connection between the pulmonary trunk and the dorsal aorta. Postnatal closure occurs initially by by smooth muscle contraction and begins at the first breath and is rapid, completed within the first day (about 15 hr after birth). Anatomical closure is much slower occuring by 2–3 weeks after birth (33% of infants), by 2 months (90% of infants) and by 1 year (99% of infants). The adult anatomical remnant of the ductus arteriosus is the ligamentum arteriosum.
  • Ductus Venosus - connects portal and umbilical blood to the inferior vena cava. Functional closure occurs postnatally within hours. Structural closure commences days after birth and completes by 18 to 20 days. The adult anatomical remnant of the ductus venosus is the ligamentum venosum (a dorsal fissure on the liver).

Premature Birth

Premature infant
Special educational need by gestational age (UK data)[12]
Year < 34 weeks % 34-36 weeks % total preterm %
1990 3.3 7.3 10.6
1995 3.3 7.7 11
2000 3.4 8.2 11.6
2005 3.6 9.1 12.7

Data: Prevention of preterm birth: a renewed national priority [13]

Australia Recommendations

Perinatal care at the borderlines of viability: a consensus statement based on a NSW and ACT consensus workshop, February 2005[14] and 2007 [15]

  • less than 23 weeks survival is minimal and the risk of major morbidity is so high that initiation of resuscitation is not appropriate.
  • 23 weeks active treatment may be discussed, but would be discouraged in NSW/ACT neonatal intensive care units.
  • 23 to 25 weeks otherwise normal infant, there is an increasing obligation to treat. However, it is acceptable medical practice not to initiate intensive care if parents so wish, following appropriate counselling.
  • 24 weeks antenatal transfer to a tertiary centre for fetal reasons is indicated. The option of non-initiation of intensive care/resuscitation should be offered.
  • 25 weeks active treatment is usually offered, but the option of non-initiation of intensive care/resuscitation (presence of adverse fetal factors such as twin-to-twin transfusion, intrauterine growth restriction or chorioamnionitis) should also be discussed.
  • 26 weeks or more otherwise normal infant the obligation to treat is very high, and treatment should generally be initiated unless there are exceptional circumstances.
"A grey zone between 23(0) and 25(6) weeks of gestation was identified and agreed upon. In this grey zone, while there was an increasing obligation to treat, it was acceptable not to initiate intensive care following appropriate counselling with parents. Important areas identified before birth, were continuing communication between the perinatal team and parents, a review of choice with continued counselling, decision support and empathy." [15]

Birth Induction

Maternal and Neonatal Outcomes of Elective Induction of Labor

AHRQ Evidence Report 2009 (USA)

  • Induction of labor is on the rise in the USA, increasing from 9.5 percent in 1990 to 22.1 percent in 2004.
  • Although, it is not entirely clear what proportion of these inductions are elective (i.e. without a medical indication), the overall rate of induction of labor is rising faster than the rate of pregnancy complications that would lead to a medically indicated induction. However, the maternal and neonatal effects of induction of labor are unclear. Many studies compare women with induction of labor to those in spontaneous labor. This is problematic, because at any point in the management of the woman with a term gestation, the clinician has the choice between induction of labor and expectant management, not spontaneous labor. Expectant management of the pregnancy involves nonintervention at any particular point in time and allowing the pregnancy to progress to a future gestational age. Thus, women undergoing expectant management may go into spontaneous labor or may require indicated induction of labor at a future gestational age.
  • Randomized controlled trials suggest that elective induction of labor at 41 weeks of gestation and beyond may be associated with a decrease in both the risk of cesarean delivery and of meconium-stained amniotic fluid. The evidence regarding elective induction of labor prior to 41 weeks of gestation is insufficient to draw any conclusion. There is a paucity of information from prospective RCTs examining other maternal or neonatal outcomes in the setting of elective induction of labor. Observational studies found higher rates of cesarean delivery with elective induction of labor, but compared women undergoing induction of labor to women in spontaneous labor and were subject to potential confounding bias, particularly from gestational age. Such studies do not inform the question of how elective induction of labor affects maternal or neonatal outcomes. Elective induction of labor at 41 weeks of gestation and potentially earlier also appears to be a cost-effective intervention, but because of the need for further data to populate these models our analyses are not definitive. Despite the evidence from the prospective, RCTs reported above, there are concerns about the translation of such findings into actual practice, thus, there is a great need for studying the translation of such research into settings where the majority of obstetric care is provided.[16]


Links: NCBI Bookshelf - Full Report | | search pubmed

Symphysiotomy

Symphysiotomy

A clinical procedure (operation) carried out to increase pelvic outlet size and to permit vaginal delivery of a baby, the surgical procedure involves dividing the cartilage of the symphysis pubis.[17][18] This can be employed for a number of birth related issues including: lack of caesarean option, obstructed birth, breech birth and shoulder dystonia.

The operation can lead to transient maternal pelvic instability. A recent Cochrane study looking at "the effectiveness and safety of symphysiotomy versus alternative options for obstructed labour in various clinical situations" identified no randomized trials of symphysiotomy.[19]


Links: Pubmed search - Symphysiotomy

Shoulder Dystocia

Term describing a birth condition where the fetal bisacromial diameter is greater than the maternal pelvic inlet antero-posterior diameter. This leads to the fetal anterior shoulder becoming impacted behind the maternal pubic symphysis. More simply, the shoulder becomes "stuck" during birth.[20] This condition generally has a low incidence[21], but can occur in up to 3% of all births and there are a range of clinical procedures employed to overcome the problem depending on the degree and stage of birth. Effects associated with this clinical condition include fetal clavicle (collar bone) breakage and brachial plexus damage.[22][23]


It is thought that the recent trend for increasing maternal obesity has in turn led to increasing fetal macrosomy that has increased shoulder dystocia and fetal clavicle breakage.

Clinical procedures: suprapubic pressure with normal downward traction on fetal head, McRoberts maneuver, Wood's screw maneuver, Posterior arm extraction and Procto-episiotomy.


Links: American Academy of Family Physicians - Shoulder Dystocia | Australia - The Royal Women’s Hospital | search pubmed

Neonatal Testing

Apgar Test

Apgar Test

A historic neonatal test designed by Dr Virginia Apgar[24] used in nearly all maternity clinics to assess the newborn infants well being assigned scores for each of 5 indicators: Heart Rate, Respiratory Effort, Reflex Irritability, Muscle Tone, Colour Measured at one and five minutes after birth the Score values are totalled for all indicators: 7-10 is considered normal, 4-7 may require resuscitative measures, 3 and below require immediate resuscitation. In recent years there has been some controversy of the relevance and accuracy of some of the criteria used in this test, though many feel it is still an invaluable initial assessment tool particularly where medical services are limited.

  • Measured at one and five minutes after birth.
  • The Score values are totalled for all indicators
    • 7 to 10 is considered normal
    • 4 to 7 may require resuscitative measures
    • 3 and below require immediate resuscitation
Indicator Score 0 Score 1 Score 2
Activity
(muscle tone)
Limp; no movement Some flexion of arms and legs Active motion
Pulse
(heart rate)
No heart rate Fewer than 100 beats per minute At least 100 beats per minute
Grimace
(reflex response)
No response to airways being suctioned Grimace during suctioning Grimace and pull away, cough, or sneeze during suctioning
Appearance
(color)
The baby's whole body is completely bluish-gray or pale Good color in body with bluish hands or feet Good color all over
Respiration
(breathing)
Not breathing Weak cry; may sound like whimpering, slow or irregular breathing Good, strong cry; normal rate and effort of breathing


Links: Apgar test

Guthrie Test

Guthrie card

A blood screening test developed by Dr Robert Guthrie (1916-95) at University of Buffalo.[25] The test is carried out on neonatal (newborn) blood detecting markers for a variety of known disorders (phenylketonuria (PKU), hypothyroidism and cystic fibrosis). In the Australian states of NSW and Victoria, the Guthrie Cards are currently stored indefinitely.

Links: Guthrie test

Abnormalities

There are many birth associated abnormalities, only a few examples are listed below. In particular the perinatal period is a time when fetal systems that have either not yet been functional (respiratory, gastrointestinal, neural) or are extensively remodelled (cardiovascular, placental). There are also a number of maternal issues.

The International Classification of Diseases (ICD) has two entire chapters committed to the childbirth and the perinatal period, the major sub-headings are shown below. More detail is available on the chapter pages, Chapter XV Pregnancy Childbirth and Chapter XVI Perinatal Period. The World Health Organization's ICD classification used worldwide as the standard diagnostic tool for epidemiology, health management and clinical purposes. This includes the analysis of the general health situation of population groups. It is used to monitor the incidence and prevalence of diseases and other health problems.

Chapter XV Pregnancy, childbirth and the puerperium (O00-O99)

The codes included in this chapter are to be used for conditions related to or aggravated by the pregnancy, childbirth or by the puerperium (maternal causes or obstetric causes)

Excludes Certain diseases or injuries complicating pregnancy, childbirth and the puerperium classified elsewhere: external causes (for mortality) (V, W, X, Y); injury, poisoning and certain other consequences of external cause (S00-T88.1, , T88.6-T98); mental and behavioural disorders associated with the puerperium (F53.-); obstetrical tetanus (A34); postpartum necrosis of pituitary gland (E23.0); puerperal osteomalacia (M83.0); supervision of high-risk pregnancy (Z35.-); supervision of normal pregnancy (Z34.-).

Chapter XVI Certain conditions originating in the perinatal period (P00-P96)

Includes conditions that have their origin in the perinatal period even though death or morbidity occurs later.

Excludes congenital malformations, deformations and chromosomal abnormalities (Q00-Q99); endocrine, nutritional and metabolic diseases (E00-E90); injury, poisoning and certain other consequences of external causes (S00-T98); neoplasms (C00-D48); tetanus neonatorum (A33)

Major sub-headings are shown below, select the sub-heading link to see details.


Links: XV Pregnancy Childbirth | International Classification of Diseases - XVI Perinatal Period | International Classification of Diseases | Human Abnormal Development

Uterine Rupture

Maternal uterine rupture is defined as an anatomic separation of the uterine muscle with or without symptoms and has adverse consequences for both mother and infant. AN NIH consensus conference[26]identified a increased risk of uterine rupture in women who have a trial of labor compared to elective repeat cesarean delivery. "There have been no reported maternal deaths due to uterine rupture. Overall, 14 to 33 percent of women will need a hysterectomy when the uterus ruptures. Approximately 6 percent of uterine ruptures will result in perinatal death. This is an overall risk of intrapartum fetal death of 20 per 100,000 women undergoing trial of labor. For term pregnancies, the reported risk of fetal death with uterine rupture is less than 3 percent. Although the risk is similarly low, there is insufficient evidence to quantify the neonatal morbidity directly related to uterine rupture."


ICD: O71.0 Rupture of uterus before onset of labour | O71.1 Rupture of uterus during labour, Rupture of uterus not stated as occurring before onset of labour | Uterus Abnormalities | Uterus Development

Amniotic Fluid Embolism

(AFE) Clinical term for a rare obstetric emergency in which conceptus material (amniotic fluid, fetal cells, hair, or other fetal debris) enter the maternal circulation from the placenta and lead to an allergic reaction followed by maternal cardiorespiratory collapse. Amniotic fluid can enter maternal circulation through tears in the uterus or cervix during labour and delivery, or through partial separation of the placenta.

A recent international study[27] has attempted to standardise how AFE data is collected and recommended:

  1. Comparisons of AFE incidence estimates should be restricted to studies using similar methodology. The recommended approaches would be either population-based database studies using additional criteria to exclude false positive cases, or tailored data collection using existing specific population-based systems.
  2. Comparisons of AFE incidence between and within countries would be facilitated by development of an agreed case definition and an agreed set of criteria to minimise inclusion of false positive cases for database studies.
  3. Groups conducting detailed population-based studies on AFE should develop an agreed strategy to allow combined analysis of data obtained using consistent methodologies in order to identify potentially modifiable risk factors.
  4. Future specific studies on AFE should aim to collect information on management and longer-term outcomes for both mothers and infants in order to guide best practice, counselling and service planning.


ICD: O88.1 Amniotic fluid embolism Anaphylactoid syndrome of pregnancy

Labor Abnormalities

  • Premature Labor - occurs 7 -10% in humans, contributes 75% perinatal mortalities
  • Underdeveloped Systems - particularly respiratory, surfactant, hyaline membrane disease (see respiratory development lecture)

Placental Abnormalities

  • placenta accreta - abnormal adherence, with absence of decidua basalis
  • placenta percreta - villi penetrate myometrium
  • placenta previa - placenta overlies internal os of uterus, abnormal bleeding, cesarian delivery

Breech Delivery

Breech Birth Breech Birth
  • Historically, breech-born children were called agrippi, meaning "delivered with difficulty" (aegre parti).
  • Breech position - occurs in about 3% of fetuses when buttocks or lower limb are presented to the birth canal rather than normal cephalic (head-first) position (presentation).
  • Associated increased - perinatal mortality, perinatal morbidity, recurrence in successive siblings

Current research suggests that genetically that both men and women delivered in breech presentation at term could also contribute to an increased risk of breech delivery in their offspring. ([#18369204 Nordtveit TI, etal., 2008])

Meconium Aspiration Syndrome

Newborn X-ray Meconium aspiration syndrome
  • meconium is formed from gut and associated organ secretions as well as cells and debris from the swallowed amniotic fluid.
  • Meconium accumulates during the fetal period in the large intestine (bowel). It can be described as being a generally dark colour (green black) , sticky and odourless.
  • Normally this meconium is defaecated (passed) postnatally over the first 48 hours and then transitional stools from day 4.
  • Abnormally this meconium is defaecated in utero, due to oxygen deprivation and other stresses. Premature discharge into the amniotic sac can lead to mixing with amniotic fluid and be reswallowed by the fetus. This is meconium aspiration syndrome and can damage both the developing lungs and placental vessels.

Necrotizing Enterocolitis

Occurs postnatally in mainly in premature and low birth weight infants (1 in 2,000 - 4,000 births). The underdeveloped gastointestinal tract appears to be susceptible to bacteria, normally found within the tract,to spread widely to other regions where they damage the tract wall and may enter the bloodstream.

References

  1. 1.0 1.1 Committee opinion no 579: definition of term pregnancy. Obstet Gynecol: 2013, 122(5);1139-40 PMID:24150030
  2. Kirsti Myklestad, Lars Johan Vatten, Elisabeth Balstad Magnussen, Kjell Asmund Salvesen, Pål Richard Romundstad Do parental heights influence pregnancy length?: a population-based prospective study, HUNT 2. BMC Pregnancy Childbirth: 2013, 13(1);33 PMID:23383756
  3. De Bie HMA, Oostrom KJ, Boersma M, Veltman DJ, Barkhof F, et al. (2011) Global and Regional Differences in Brain Anatomy of Young Children Born Small for Gestational Age. PLoS ONE 6(9): e24116. doi:10.1371/journal.pone.0024116 PLoS ONE
  4. Does Birth Weight Influence Physical Activity in Youth? A Combined Analysis of Four Studies Using Objectively Measured Physical Activity PMC3020226
  5. Ruth M Hadfield, Samantha J Lain, Judy M Simpson, Jane B Ford, Camille H Raynes-Greenow, Jonathan M Morris, Christine L Roberts Are babies getting bigger? An analysis of birthweight trends in New South Wales, 1990-2005. Med. J. Aust.: 2009, 190(6);312-5 PMID:19296812
  6. William A Engle, American Academy of Pediatrics Committee on Fetus and Newborn Age terminology during the perinatal period. Pediatrics: 2004, 114(5);1362-4 PMID:15520122 | Pediatrics
  7. R Mittendorf, M A Williams, C S Berkey, P F Cotter The length of uncomplicated human gestation. Obstet Gynecol: 1990, 75(6);929-32 PMID:2342739
  8. USA National Vital Statistics System - Birth Data
  9. Jane E Norman, Carole Morris, James Chalmers The effect of changing patterns of obstetric care in Scotland (1980-2004) on rates of preterm birth and its neonatal consequences: perinatal database study. PLoS Med.: 2009, 6(9);e1000153 PMID:19771156
  10. Piotr Pierzynski, Edward Oczeretko, Piotr Laudanski, Tadeusz Laudanski New research models and novel signal analysis in studies on preterm labor: a key to progress? BMC Pregnancy Childbirth: 2007, 7 Suppl 1;S6 PMID:17570166 | BMC Pregnancy Childbirth.
  11. Pierre M Barker, Richard E Olver Invited review: Clearance of lung liquid during the perinatal period. J. Appl. Physiol.: 2002, 93(4);1542-8 PMID:12235057
  12. Daniel F MacKay, Gordon C S Smith, Richard Dobbie, Jill P Pell Gestational age at delivery and special educational need: retrospective cohort study of 407,503 schoolchildren. PLoS Med.: 2010, 7(6);e1000289 PMID:20543995 | PLoS Medicine
  13. Karla Damus Prevention of preterm birth: a renewed national priority. Curr. Opin. Obstet. Gynecol.: 2008, 20(6);590-6 PMID:18989136
  14. Kei Lui, Barbara Bajuk, Kirsty Foster, Arnolda Gaston, Alison Kent, John Sinn, Kaye Spence, Wendy Fischer, David Henderson-Smart Perinatal care at the borderlines of viability: a consensus statement based on a NSW and ACT consensus workshop. Med. J. Aust.: 2006, 185(9);495-500 PMID:17137454 | eMJA
  15. 15.0 15.1 Alison L Kent, Anne Casey, Kei Lui, NSW and ACT Perinatal Care at the Borderlines of Viability Consensus Workshop Committee Collaborative decision-making for extreme premature delivery. J Paediatr Child Health: 2007, 43(6);489-91 PMID:17535182
  16. Aaron B Caughey, Vandana Sundaram, Anjali J Kaimal, Yvonne W Cheng, Allison Gienger, Sarah E Little, Jason F Lee, Luchin Wong, Brian L Shaffer, Susan H Tran, Amy Padula, Kathryn M McDonald, Elisa F Long, Douglas K Owens, Dena M Bravata Maternal and neonatal outcomes of elective induction of labor. Evid Rep Technol Assess (Full Rep): 2009, (176);1-257 PMID:19408970 | NCBI Bookshelf - Full Report
  17. Douwe Arie Anne Verkuyl Think globally act locally: the case for symphysiotomy. PLoS Med.: 2007, 4(3);e71 PMID:17388656
  18. Hege Langli Ersdal, Douwe A A Verkuyl, Kenneth Björklund, Staffan Bergström Symphysiotomy in Zimbabwe; postoperative outcome, width of the symphysis joint, and knowledge, attitudes and practice among doctors and midwives. PLoS ONE: 2008, 3(10);e3317 PMID:18846216
  19. G Justus Hofmeyr, P Mike Shweni Symphysiotomy for feto-pelvic disproportion. Cochrane Database Syst Rev: 2010, (10);CD005299 PMID:20927742
  20. Robert H Allen On the mechanical aspects of shoulder dystocia and birth injury. Clin Obstet Gynecol: 2007, 50(3);607-23 PMID:17762413
  21. Jessica Rahman, Ghias Bhattee, Mohammad Sayedur Rahman Shoulder dystocia in a 16-year experience in a teaching hospital. J Reprod Med: 2009, 54(6);378-84 PMID:19639928
  22. John Andersen, Joe Watt, Jaret Olson, John Van Aerde Perinatal brachial plexus palsy. Paediatr Child Health: 2006, 11(2);93-100 PMID:19030261
  23. Suneet P Chauhan, Jill Cole, M Ryan Laye, Ken Choi, Maureen Sanderson, R Clifton Moore, Everett F Magann, Holly L King, John C Morrison Shoulder dystocia with and without brachial plexus injury: experience from three centers. Am J Perinatol: 2007, 24(6);365-71 PMID:17566948
  24. V APGAR A proposal for a new method of evaluation of the newborn infant. Curr Res Anesth Analg: 1953, 32(4);260-7 PMID:13083014
  25. R GUTHRIE, A SUSI A SIMPLE PHENYLALANINE METHOD FOR DETECTING PHENYLKETONURIA IN LARGE POPULATIONS OF NEWBORN INFANTS. Pediatrics: 1963, 32;338-43 PMID:14063511
  26. NIH Consensus Development Conference on Vaginal Birth After Cesarean: New Insights. March 8–10, 2010, Bethesda, Maryland. Statement
  27. Marian Knight, Cynthia Berg, Peter Brocklehurst, Michael Kramer, Gwyneth Lewis, Jeremy Oats, Christine L Roberts, Catherine Spong, Elizabeth Sullivan, Jos van Roosmalen, Joost Zwart Amniotic fluid embolism incidence, risk factors and outcomes: a review and recommendations. BMC Pregnancy Childbirth: 2012, 12;7 PMID:22325370 | BMC Pregnancy Childbirth.

Reviews

Articles

Daniel F MacKay, Gordon C S Smith, Richard Dobbie, Jill P Pell Gestational age at delivery and special educational need: retrospective cohort study of 407,503 schoolchildren. PLoS Med.: 2010, 7(6);e1000289 PMID:20543995 | PLoS

Search Pubmed

Search Pubmed: Birth | Parturition | Fetal Changes Birth

Birth Terms

amniotomy - birth medical procedure thought to speed labor, where the amniotic sac is artificially ruptured using a tool (amniohook).

breech - fetal buttocks presented first and can also occur in different forms depending on presentation (complete breech, frank breech, footing breech, knee breech).

decidual activation - increased uterine proteolysis and extracellular matrix degradation.

dilatation - opening of the cervix in preparation for birth (expressed in centimetres).

effacement - shortening or thinning of the cervix, in preparation for birth.

forceps - mechanical "plier-like" tool used on fetal head to aid birth.

fetal macrosomia - clinical description for a fetus that is too large, condition increases steadily with advancing gestational age and defined by a variety of birthweights. In pregnant women anywhere between 2 - 15% have birth weights of greater than 4000 grams (4 Kg, 8 lb 13 oz).

membrane rupture - breaking of the amniotic membrane and release of amniotic fluid (water breaking).

morbidity - (Latin, morbidus = "sick" or "unhealthy") refers to a diseased state, disability, or poor health due to any cause.

presentation - how the fetus is situated in the uterus.

presenting part - part of fetus body that is closest to the cervix.

second stage of labour - passage of the baby through the birth canal into the outside world.

Vacuum Extractor - suction cap device used on fetal head to aid birth.

Vertex Presentation (cephalic presentation) where the fetus head is the presenting part, most common and safest birth position.

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name.


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Cite this page: Hill, M.A. (2014) Embryology Birth. Retrieved July 3, 2014, from //php.med.unsw.edu.au/embryology/index.php?title=Birth

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Dr Mark Hill 2014, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G