COMBINATION OF ELEVATED MATERNAL SERUM ALPHA-FETOPROTEIN (MSAFP) AND LOW ESTRIOL IS HIGHLY PREDICTIVE OF ANENCEPHALY

Increased levels of second trimester maternal serum alpha-fetoprotein (MSAFP) have long been established as a marker for neural tube defects (NTDs), In addition, decreased levels of maternal estriol in the thir d trimester have been reported in pregnancies with anencephalic fetuse s, The purpose of this study was to evaluate whether early second trim ester unconjugated serum estriol (uE3) is an independent predictor of NTDs, The study included 57,031 patients who underwent maternal serum screening with MSAFP at 14-22 weeks gestation, Of these, 23,415 also h ad uE3 measurements, There were 63 cases of NTD, an overall incidence of 1.1 per 1,000, Elevated MSAFP (greater than or equal to 2.5 MOM) wa s detected in 1,346 patients, 48 of which had NTDs, Decreased uE3 (les s than or equal to 0.5) was detected in 1,437 patients, 17 of which ha d NTDs, The incidence of NTDs was significantly higher in patients wit h low uE3, compared to patients with normal/high uE3 (1.15% vs, 0.09%, P < 001), Finally, 51 patients had both increased MSAFP and decreased uE3; 16 of these had NTDs, 14 of which were anencephalics, In conclus ion, both elevated MSAFP and low maternal serum estriol are predictive of NTD but have a low sensitivity, The combination of abnormally elev ated MSAFP and low estriol is highly predictive of NTD in particular a nencephaly. (C) 1998 Wiley-Liss, Inc.