Medically assisted reproduction and second-trimester maternal serum marker screening for Down syndrome.

Objectives: To evaluate the effect of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) on total hCG, free ss-hCG, AFP and unconjugated estriol (uE3) used as markers for second-trimester Down syndrome maternal serum screening.

Methods: Second-trimester maternal sera from 1515 singleton pregnancies (970 by IVF, 545 by ICSI) were compared with control sera (21 014 cases). Free ss-hCG, total hCG, AFP and uE3 were compared between the control group and the medically assisted reproduction groups.

Very low alpha-fetoprotein in Down syndrome maternal serum screening.

Objective: To establish the frequency of very low maternal serum AFP and to differentiate congenital AFP deficiency from those diseases known to be associated with low AFP.

Methods: AFP values below 2 microg/L and borderline values up to 3 microg/L were retrospectively analysed in 839 773 singleton pregnancies included in a programme for routine screening of trisomy 21 maternal serum markers.

Results: Serum AFP was undetectable (< or =2 microg/L) in 8 cases, giving a frequency of 1/105 000.

Second trimester two-step trisomy 18 screening using maternal serum markers.

Trisomy 21 maternal serum marker screening has led to screening for other anomalies, including trisomy 18. Trisomy 18 is generally prenatally diagnosed because of major morphological defects. However, in up to 30% of cases ultrasound signs are unclear, and in most cases diagnosis is performed late in pregnancy.