Birth - Preterm
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Preterm delivery (PTD) is defined as birth before 37 completed weeks of gestation (GA). In the USA the preterm birth rate declined in 2008 to 12.3 percent, from 12.8 percent in 2006. The preterm birth rates also declined from 2006 to 2008 for mothers of all age groups under age 40. Very premature infants have associated clinical problems that may include: neonatal respiratory distress syndrome, bronchopulmonary dysplasia, cerebroventricular haemorrhage and a range of brain pathologies. Risk factors for mothers include a prior history of preterm birth, underweight, obesity, diabetes, high blood pressure, smoking, infection, age (either under 17 or over 40), genetics, multiple pregnancy (twins, triplets, and more) and pregnancies spaced too closely together.
- In the United States, more than 30,000 babies per year are born before the 28th week of pregnancy.
- Birth Links: Introduction | Lecture - Birth | Caesarean | Birth Statistics | Australian Birth Data | Preterm | Birth-Weight | Developmental Origins of Health and Disease | Macrosomia | Neonatal Diagnosis | Stillbirth and Perinatal Death | ICD-10 Perinatal Period | Category:Birth
Some Recent Findings
|Year||< 34 weeks %||34-36 weeks %||total preterm %|
Data from: Prevention of preterm birth: a renewed national priority Damus K. Curr Opin Obstet Gynecol. 2008 Dec;20(6):590-6 PMID: 18989136
Growth Chart for Preterm Babies
- 1976 - the Babson and Benda "fetal-infant growth graph" for preterm infants was commonly used in neonatal intensive care.
- 1996 - the Beeby graph based upon New South Wales Midwives Data Collection (MDC) from 1990 to 1994 inclusive (n = 422139).
- 1999 - the National Institute of Child Health and Human Development Neonatal Research Network (NICHD) USA graph.
- 2003 - improved version of the Babson and Benda graph based upon literature review and intrauterine data.
Australia Preterm Birth
Patterns and outcomes of preterm hospital admissions during pregnancy in NSW, 2001-2008
NSW is the largest by population of all Australian states (7,238,819 or 32.4% 2010 estimate). The following information is from the abstract of the above paper published in March 2012.
- Women who were admitted to hospital in weeks 20-36 of pregnancy (preterm) and gave birth to a liveborn singleton infant in New South Wales during 2001-2008. Numbers of preterm admissions of pregnant women who were discharged without giving birth, were transferred to higher care, or who gave birth.
- 110 439 pregnancies (16.0%) involved at least one preterm admission. After their initial preterm admission:
- 71.9% of women were discharged.
- 6.3% were transferred.
- 21.8% gave birth.
- Median gestational age at admission was 33 weeks and median time to discharge, transfer or giving birth was 1 day.
- Of the women who were admitted or were transferred with suspected preterm labour, only 29% and 38%, respectively, gave birth.
- As gestational age increased, the proportion of women transferred decreased and the proportion giving birth increased.
USA Preterm Birth
Late preterm birth"The American College of Obstetricians and Gynecologists suggests that preterm birth rates have also increased because of a dramatic rise in late preterm births, defined as births between 34 weeks and 36-6/7 weeks of gestation. Late preterm newborns are the fastest growing subset of neonates, accounting for approximately 74% of all preterm births and about 8% of total births."
USA Preterm Birth Rate
Preterm birth rates per 100 births in each specified gestational age category.
|Total preterm||Extremely preterm||Early preterm||Late preterm|
|less than 37 weeks’ gestation||less than 28 weeks’ gestation||less than 34 weeks’ gestation||34–36 weeks’ gestation|
- Data: USA Preterm birth rates national Vital Statistics System, United States, 2007.
See also Preterm Birth: Causes, Consequences, and Prevention (2007).
- Links: USA Statistics
Ultrasound Short Cervix
Evaluation of the cervical morphology and biometry with transvaginal ultrasonography at 16-24 weeks of gestation is a useful tool to predict the risk of preterm birth in low- and high-risk singleton pregnancies. The following points are from a recent review on transvaginal sonography for both the prediction and management of spontaneous preterm labour.
Cervical Length (CV)
- > 30 mm - present cervical gland area have a 96-97% negative predictive value for preterm delivery at <37 weeks.
- ≤25 mm - irrespective of other risk factors, use of progesterone.
- ≤ 25 mm - asymptomatic cervical shortening with prior spontaneous preterm delivery, prophylactic cerclage procedure should be performed.
When given to mothers in preterm labour, dexamethosone, a steroid used to treat asthma, helps speed up the development of the baby’s lungs. At a cost of about US$1, two shots can stop premature babies from going into respiratory distress when they are born. This can prevent 400,000 deaths annually.
Kangaroo Mother Care
A neonatal care technique involving holding the infant skin-to-skin on the mother's chest, keeping the baby warm and facilitates breastfeeding.
Keeping preterm babies warm is especially important because their tiny bodies lose heat rapidly, making them highly vulnerable to illness, infection and death. This could prevent 450 000 deaths annually.
Epsom Salt (magnesium sulfate, magnesium sulphate) is an inorganic salt originally used to inhibit labor (labor-inhibiting), slowing or halting uterine contractions (tocolytic agent). Inhibitory mechanism not clear, but thought to; compete with calcium at the level of plasma membrane voltage-gated channels, hyperpolarize the plasma membrane, inhibit myosin light-chain kinase activity by competing with intracellular calcium.
While described as not effective for inhibiting labor, it has more recently been recommended for neuroprotection in very preterm birth. (magnesium sulphate)
Preterm delivery and overview of related potential fetal and neonatal effects on lung development. 
- Links: Respiratory Abnormalities
A recent UK population-based study "These findings show that gestational age at delivery strongly affects a child's subsequent risk of having an special educational need (SEN) in a dose-dependent manner across the whole range of gestational age. Furthermore, because early term delivery is much more common than preterm delivery, these findings show that early term delivery is responsible for more cases of SEN than preterm delivery."
The following text information is from a recent systematic review and meta-analyses of maternal obesity
What is already known on this topic
- The effect of overweight or obesity in women on risk of preterm birth is debated in the literature
- Uncertainty is reflected in national guidelines, although it is widely believed that the risk of having an infant of low birth weight is decreased in overweight or obese women
What this study adds
- Overweight or obese women have increased risks of preterm birth before 32 weeks and induced preterm birth before 37 weeks, and, accounting for publication bias, preterm birth before 37 weeks overall
- The beneficial effects of overweight or obesity on low birth weight were greater in developing than developed countries and disappeared after accounting for publication bias
- Overweight and obese women should be counselled before pregnancy on their perinatal risks, and appropriate surveillance should be considered during pregnancy
Bacterial Infection Fetal Membranes
- Differing prevalence and diversity of bacterial species in fetal membranes from very preterm and term labor.
- "Intrauterine infection may play a role in preterm delivery due to spontaneous preterm labor (PTL) and preterm prolonged rupture of membranes (PPROM). Because bacteria previously associated with preterm delivery are often difficult to culture, a molecular biology approach was used to identify bacterial DNA in placenta and fetal membranes. ...A greater spread and diversity of bacterial species were found in tissues of women who had very preterm births. It is unclear to what extent the greater bacterial prevalence observed in all vaginal delivery groups reflects bacterial contamination or colonization of membranes during labor. Bacteria positive preterm tissues are associated with histological chorioamnionitis and a pronounced maternal immune paresis."
- Screening to prevent spontaneous preterm birth.
- "For primary prevention, an effective, affordable and safe intervention applied to all mothers without preceding testing is likely to be the most cost-effective approach in asymptomatic women in early pregnancy. For secondary prevention among women at risk of preterm labour in later pregnancy, a management strategy based on the results of testing is likely to be more cost-effective."
Inhaled Nitric Oxide Therapy
NIH Consensus Development Conference (2010) conclusions
- Taken as a whole, the available evidence does not support use of inhaled nitric oxide in early routine, early rescue, or later rescue regimens in the care of premature infants <34 weeks gestation who require respiratory support.
- There are rare clinical situations, including pulmonary hypertension or hypoplasia, that have been inadequately studied in which inhaled nitric oxide may have benefit in infants <34 weeks gestation. In such situations, clinicians should communicate with families regarding the current evidence on its risks and benefits as well as remaining uncertainties.
- Basic research and animal studies have contributed to important understandings of inhaled nitric oxide benefits on lung development and function in infants at high risk of bronchopulmonary dysplasia. These promising results have only partly been realized in clinical trials of inhaled nitric oxide treatment in premature infants. Future research should seek to understand this gap.
- Predefined subgroup and post hoc analyses of previous trials showing potential benefit of inhaled nitric oxide have generated hypotheses for future research for clinical trials. Prior strategies shown to be ineffective are discouraged unless new evidence emerges. The positive results of one multicenter trial, which was characterized by later timing, higher dose, and longer duration of treatment, require confirmation. Future trials should attempt to quantify the individual effects of each of these treatment-related variables (timing, dose, and duration), ideally by randomizing them separately.
- Based on assessment of currently available data, hospitals, clinicians, and the pharmaceutical industry should avoid marketing inhaled nitric oxide for premature infants <34 weeks gestation.
- Links: NIH Consensus Development Conference: Inhaled Nitric Oxide Therapy for Premature Infants October 27-29, 2010 | draft consensus statement
- ↑ Born Too Soon: The Global Action Report on Preterm Birth
- ↑ 2.0 2.1 H Honest, C A Forbes, K H Durée, G Norman, S B Duffy, A Tsourapas, T E Roberts, P M Barton, S M Jowett, C J Hyde, K S Khan Screening to prevent spontaneous preterm birth: systematic reviews of accuracy and effectiveness literature with economic modelling. Health Technol Assess: 2009, 13(43);1-627 PMID:19796569
- ↑ NCHS Data Brief Number 39, May 2010
- ↑ Born Too Soon: The Global Action Report on Preterm Birth
- ↑ Ali Khatibi, Anne-Lise Brantsaeter, Verena Sengpiel, Marian Kacerovsky, Per Magnus, Nils-Halvdan Morken, Ronny Myhre, Nina Gunnes, Bo Jacobsson Prepregnancy maternal body mass index and preterm delivery. Am. J. Obstet. Gynecol.: 2012, 207(3);212.e1-7 PMID:22835494
- ↑ Kimberly G Noble, William P Fifer, Virginia A Rauh, Yoko Nomura, Howard F Andrews Academic Achievement Varies With Gestational Age Among Children Born at Term. Pediatrics: 2012; PMID:22753563
- ↑ Chiara Nosarti, Abraham Reichenberg, Robin M Murray, Sven Cnattingius, Mats P Lambe, Li Yin, James Maccabe, Larry Rifkin, Christina M Hultman Preterm Birth and Psychiatric Disorders in Young Adult LifePreterm Birth and Psychiatric Disorders. Arch Gen Psychiatry: 2012;610-617 PMID:22660967
- ↑ 8.0 8.1 Tim Badgery-Parker, Jane B Ford, Mary G Jenkins, Jonathan M Morris, Christine L Roberts Patterns and outcomes of preterm hospital admissions during pregnancy in NSW, 2001-2008. Med. J. Aust.: 2012, 196(4);261-5 PMID:22409693 | Med J Aust
- ↑ Naomi K Tepper, Sherry L Farr, Bruce B Cohen, Angela Nannini, Zi Zhang, John E Anderson, Denise J Jamieson, Maurizio Macaluso Singleton preterm birth: risk factors and association with assisted reproductive technology. Matern Child Health J: 2012, 16(4);807-13 PMID:21516300
- ↑ Ali S Khashan, Philip N Baker, Louise C Kenny Preterm birth and reduced birthweight in first and second teenage pregnancies: a register-based cohort study. BMC Pregnancy Childbirth: 2010, 10();36 PMID:20618921
- ↑ 11.0 11.1 Sarah D McDonald, Zhen Han, Sohail Mulla, Joseph Beyene, Knowledge Synthesis Group Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: systematic review and meta-analyses. BMJ: 2010, 341();c3428 PMID:20647282 | BMJ
- ↑ 12.0 12.1 Tanis R Fenton A new growth chart for preterm babies: Babson and Benda's chart updated with recent data and a new format. BMC Pediatr: 2003, 3();13 PMID:14678563 | BMC Pediatr.
- ↑ S G Babson, G I Benda Growth graphs for the clinical assessment of infants of varying gestational age. J. Pediatr.: 1976, 89(5);814-20 PMID:978333
- ↑ P J Beeby, T Bhutap, L K Taylor New South Wales population-based birthweight percentile charts. J Paediatr Child Health: 1996, 32(6);512-8 PMID:9007782
- ↑ R A Ehrenkranz, N Younes, J A Lemons, A A Fanaroff, E F Donovan, L L Wright, V Katsikiotis, J E Tyson, W Oh, S Shankaran, C R Bauer, S B Korones, B J Stoll, D K Stevenson, L A Papile Longitudinal growth of hospitalized very low birth weight infants. Pediatrics: 1999, 104(2 Pt 1);280-9 PMID:10429008
- ↑ Ryan W Loftin, Mounira Habli, Candice C Snyder, Clint M Cormier, David F Lewis, Emily A Defranco Late preterm birth. Rev Obstet Gynecol: 2010, 3(1);10-9 PMID:20508778
- ↑ Institute of Medicine (US) Committee on Understanding Premature Birth and Assuring Healthy Outcomes; Behrman RE, Butler AS, editors. Preterm Birth: Causes, Consequences, and Prevention. Washington (DC): National Academies Press (US); 2007. Available from: http://www.ncbi.nlm.nih.gov/books/NBK11362
- ↑ Resul Arisoy, Murat Yayla Transvaginal sonographic evaluation of the cervix in asymptomatic singleton pregnancy and management options in short cervix. J Pregnancy: 2012, 2012();201628 PMID:22523687 | J Pregnancy
- ↑ Born Too Soon: The Global Action Report on Preterm Birth
- ↑ Born Too Soon: The Global Action Report on Preterm Birth
- ↑ Lex W Doyle Antenatal magnesium sulfate and neuroprotection. Curr. Opin. Pediatr.: 2012, 24(2);154-9 PMID:22227787
- ↑ A H Jobe, M Ikegami Antenatal infection/inflammation and postnatal lung maturation and injury. Respir. Res.: 2001, 2(1);27-32 PMID:11686862 | PMC59566 | Respir Res.
- ↑ 23.0 23.1 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
- ↑ Hannah E Jones, Kathryn A Harris, Malika Azizia, Lindsay Bank, Bernadette Carpenter, John C Hartley, Nigel Klein, Donald Peebles Differing prevalence and diversity of bacterial species in fetal membranes from very preterm and term labor. PLoS ONE: 2009, 4(12);e8205 PMID:19997613
Institute of Medicine (US) Committee on Understanding Premature Birth and Assuring Healthy Outcomes; Behrman RE, Butler AS, editors. Preterm Birth: Causes, Consequences, and Prevention. Washington (DC): National Academies Press (US); 2007. Available from: Bookshelf
Likis FE, Andrews JC, Woodworth AL, et al. Progestogens for Prevention of Preterm Birth [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2012 Sep. (Comparative Effectiveness Reviews, No. 74.) Available from: Bookshelf PMID 23101048
Thirawut Khanprakob, Malinee Laopaiboon, Pisake Lumbiganon, Ussanee S Sangkomkamhang Cyclo-oxygenase (COX) inhibitors for preventing preterm labour. Cochrane Database Syst Rev: 2012, 10();CD007748 PMID:23076936
Frances E Likis, Digna R Velez Edwards, Jeffrey C Andrews, Alison L Woodworth, Rebecca N Jerome, Christopher J Fonnesbeck, J Nikki McKoy, Katherine E Hartmann Progestogens for preterm birth prevention: a systematic review and meta-analysis. Obstet Gynecol: 2012, 120(4);897-907 PMID:22955308
Zarko Alfirevic, Stephen J Milan, Stefania Livio Caesarean section versus vaginal delivery for preterm birth in singletons. Cochrane Database Syst Rev: 2012, 6();CD000078 PMID:22696314
Silvia Iacobelli, Elsa Kermorvant-Duchemin, Francesco Bonsante, Alexandre Lapillonne, Jean-Bernard Gouyon Chloride Balance in Preterm Infants during the First Week of Life. Int J Pediatr: 2012, 2012();931597 PMID:22505945
July 2010 "Preterm Birth" All (31665) Review (3598) Free Full Text (4781)
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.
- WHO Report 2012 Born Too Soon: The Global Action Report on Preterm Birth
- The Partnership (PMNCH) - joins the maternal, newborn and child health (MNCH) communities into an alliance of more than 350 members to ensure that all women, infants and children not only remain healthy, but thrive. Born Too Soon: The Global Action Report on Preterm Birth
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Cite this page: Hill, M.A. (2014) Embryology Birth - Preterm. Retrieved March 15, 2014, from http://embryology.med.unsw.edu.au/embryology/index.php?title=Birth_-_Preterm
- Dr Mark Hill 2014, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G