ELEVATED ALPHA-FETOPROTEIN AND HUMAN CHORIONIC-GONADOTROPIN AS A MARKER FOR PLACENTAL TRISOMY 16 IN THE 2ND TRIMESTER

In a series of 2961 consecutive cases with second-trimester biochemica l triple screening for Down's syndrome and neural tube defect (NTD), t en (0.3 per cent) showed an apparent increased risk for both condition s. Three cases had chromosomal abnormalities, namely trisomy 16 confin ed to the placenta. Since placental trisomy 16 as well as cases with i ncreased alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG ) are associated with (intrauterine growth retardation (IUGR), oligohy dramnios, and fetal demise, at least some cases with this atypical bio chemical profile could be explained by this chromosomal abnormality. F rom our results we recommend that in cases with increased risk for bot h Down's syndrome and NTD, fetal karyotyping should preferably be done on a placental biopsy, especially when ultrasound in the absence of a nomalies demonstrates early IUGR.