BGDA Practical Placenta - Diagnostic Techniques

Fetus in Utero Between fifth and sixth months

Chorionic Villus Sampling

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. Links: Chorionic villus sampling

Amniocentesis

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 %. Links: Amniocentesis

| 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.

Human term placental volumes sorted by size (from table).

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).

Additional Information

Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.

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

Terms

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Cite this page: Hill, M.A. (2024, May 4) Embryology BGDA Practical Placenta - Diagnostic Techniques. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDA_Practical_Placenta_-_Diagnostic_Techniques

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G