Abnormal levels of maternal serum human chorionic gonadotropin and alpha‐fetoprotein in the second trimester: Relation to fetal weight and preterm delivery

Abstract

The aim of this prospective descriptive cross-sectional study was to examine the clinical significance of abnormal maternal serum human chorionic gonadotropin (MShCG) and alpha-fetoprotein (MSAFP) in the second trimester of pregnancy. The study group comprised 8892 women with a singleton pregnancy, who were screened for a neural tube defect and Down's syndrome. Exclusion criteria were unknown pregnancy outcome, a congenital anomaly, delivery before 25 weeks of amenorrhoea, or known insulin-dependent diabetes. MSAFP and MShCG were determined between 15 and 20 weeks' amenorrhoea. An abnormal result was defined as (a) MSAFP or MShCG > or = 2.5 MOM, (b) MSAFP or MShCG < or = 0.5 MOM, and (c) MSAFP and MShCG > or = 2.5 MOM. Birth weight percentiles and the duration of amenorrhoea at the time of delivery were employed as outcome parameters. Of the women with an abnormally elevated MSAFP, 9.4 per cent had an extremely small-for-gestational age (SGA) infant (< 2.3rd percentile; P < 0.01, relative risk 4.5), 27.1 per cent had an SGA infant (< tenth percentile; P < 0.01, relative risk 2.7), and 14.3 per cent had an appropriate-for-gestational age (AGA) infant that was delivered preterm (< 259 days; P < 0.01, relative risk 2.4). In the cases where the MShCG level was elevated, 4.4 per cent had an extremely SGA infant (P < 0.01, relative risk 2.1) and 15.5 per cent had an SGA infant (P < 0.01, relative risk 1.5). No significant association was found between an elevated MShCG level and preterm delivery. Low MShCG was significantly associated with SGA infants (P < 0.01, relative risk 1.2) but not with extremely SGA or preterm deliveries. In the group whose MSAFP and MShCG levels were both elevated, 23.8 per cent delivered an extremely SGA infant (P < 0.01, relative risk 10.9), 38.1 per cent an SGA infant (P < 0.01, relative risk 3.7) and 47.6 per cent had a preterm delivery or an SGA infant (P < 0.01, relative risk 3.0). Isolated or combined elevation of the MSAFP and MShCG levels in the second trimester of pregnancy is an indication for extra vigilance during further prenatal care. This applies to a lesser extent to a low MShCG level.