BGDA Practical Placenta - Diagnostic Techniques
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Chorionic Villus Sampling
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Chorionic Villus Sampling test is done in the 10th to 12th week after the first day of the mother's last menstrual period. The test is done by looking at cells taken from the chorionic membrane or placenta. No anaesthetic is required, and a test result is usually available in two to three weeks.
When the test is carried out by an obstetrician experienced in the technique, the risk of miscarriage related to the test is about 2%. Potential disadvantages include maternal cell contamination, placental mosaicism and failure to obtain an adequate specimen. This may result in the need for a repeat procedure or amniocentesis.
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Amniocentesis
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Amniocentesis is a prenatal diagnostic test carried out mainly between 14th to 18th week of pregnancy. Amniotic fluid is taken from the uterus, sent to a diagnostic laboratory and embryonic cells isolated from the amniotic fluid. No anaesthetic is required, and a result is usually obtained in about three to four weeks. When the test is carried out by an obstetrician experienced in the technique, the risk of a miscarriage related to the test is about 1 %.
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- Diagnosis Links: Prenatal Diagnosis | Pregnancy Test | Amniocentesis | Chorionic villus sampling | Ultrasound | Alpha-Fetoprotein | Pregnancy-associated plasma protein-A | Fetal Blood Sampling | Magnetic Resonance Imaging | Computed Tomography | Preimplantation Genetic Screening | Comparative Genomic Hybridization | Neonatal Diagnosis | Category:Prenatal Diagnosis | Fetal Surgery | Category:Neonatal Diagnosis | Placenta - Amnionic Sac
Placenta Term Parameters
There are a variety of diagnostic and morphological measurements that can be made of the placenta during pregnancy and at term.
Simple measurements of overall placental diameter, thickness and volume:
- placental diameter - is measured in the transverse section by calculating the maximum dimensions of the chorionic surface.
- placental thickness - is measured at its mid-portion from the chorionic plate to the basilar plate, on a longitudinal plane (less than 4 cm at term). Excludes any abnormalities (fibroids, myometrial contractions, or venous lakes). The placental thickness approximates in millimeters to the weeks of gestation.
- placental volume - is measured by a range of different methods and calculations, more recently with three-dimensional ultrasound.
Additional Information
- Content shown under this heading is not part of the material covered in the practical class. It is provided for those students who would like to know about some concepts or current research in topics related to the current practical class page.
Term placental composition, villous capillarization and the mean cross-sectional areas of peripheral villi and capillaries, data from a study sample of 15 normal placenta (mean placental volume, 652 ml). [1]
| Variable | Unit | Placenta (mean, n = 15) |
| Intervillous space | mL | 213 |
| Stem villi | mL | 71.4 |
| Peripheral villi | mL | 326 |
| Trophoblast | mL | 95.5 |
| Stroma | mL | 184 |
| Fetal capillaries | mL | 46.9 |
| Non-parenchyma | mL | 41.5 |
| Peripheral villi | km | 89.2 |
| Fetal capillaries | km | 310 |
| TS area villi | µm2 | 3700 |
| TS area capillary | µm2 | 150 |
| Capillaries | mL mL-1 | 0.147 |
| Length ratio | km km-1 | 3.6 |
- ↑ Terry M Mayhew A stereological perspective on placental morphology in normal and complicated pregnancies. J. Anat.: 2009, 215(1);77-90 PMID:19141109
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Cite this page:
Hill, M.A. (2013) BGDA Practical Placenta - Diagnostic Techniques. Retrieved June 18, 2013, from http://php.med.unsw.edu.au/embryology/index.php?title=BGDA_Practical_Placenta_-_Diagnostic_Techniques
- Dr Mark Hill 2013, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
