Amniocentesis and CVS

Question 1

Amniocentesis and CVS - miscarriage risk

Answer 1

Singleton <0.5%
Twins 1%

Risk may be higher with less skilled operators and where the fetus has a chromosomal, genetic or structural abnormality

Question 2

Amniocentesis - when to perform

Answer 2

From 15+0 weeks

Before 15+0 - higher risk of pregnancy loss + risk of talipes equinovarus

Early amnio = 3% requirement for multiple needle insertions + cytogenetic implications (failed culture and potential false negatives)

Question 3

CVS - when to perform

Answer 3

11+0 and 13+6 weeks

NOT before 10+0 - possible association oromandibular and limb defects

Technically difficult before 11+0
If required can be carried out 14+0 to 14+6

Question 4

Evidence for Pregnancy Loss after Amnio/CVS - Level 1

Answer 4

Amniocentesis -
Tabor et al 1986 - 1% additional risk of pregnancy loss (imprecise - 95% CI included no additional risk and 2% risk)

CVS -
Medical Research Council 1991 AND
Smidt-Jensen et al 1993
Compared CVS to amniocentesis - increase in overall pregnancy loss (11.1% versus 8.2%; RR 1.43, 95% CI 1.22–1.67)

Question 5

Amnio/CVS - Confined placental mosaicism

Answer 5

1-2% cases affected by confined placental mosaicism
If no structural anomalies + QFPCR suggestive of a chromosomal anomaly need to await full karytopye

If structural anomalies - appropriate to discuss further care/ TOP

Question 6

Amnio/CVS - Risk of maternal sepsis

Answer 6

Rare complication

Cloudy/ purulent amniotic fluid - send small quantity of amniotic fluid for microbiological analysis and consider antibiotic treatment.

Question 7

Amnio/CVS - Multiple pregnancy

Answer 7

Pregnancy needs to be mapped with care
Operator should be skilled in selective termination if conducting mapping - not to refer to other operator to perform termination based on someone else’s mapping
Avoid labelling by numbers
If no clearly identifiable USS difference (structural anomaly, sex, etc) - 2 operators should confirm labelling

Question 8

Amnio/CVS - Multiple pregnancy - single or double uterine entry?

Answer 8

No difference

Question 9

Amnio/CVS - 3rd trimester

Answer 9

Used for newly identified fetal structural anomalies, suspected fetal infection and fetal growth restriction

Serious complications, requiring emergency birth are unusual
Increased risk of requiring more than one needle insertion
Increased risk of culture failure