title: The effect of fetal gender on second-trimester maternal serum inhibin-A concentration.
abstract: Second-trimester serum inhibin-A is increasingly used as a fourth marker in addition to the triple test to screen for Down syndrome. We investigated whether fetal gender had an effect on serum inhibin-A concentration. A retrospective analysis was done on 316 normal pregnancies and 48 Down syndrome pregnancies in which maternal serum inhibin-A assays were performed between 15 and 20 weeks of gestation and in which the fetal sex was known. The median inhibin-A MoM (95% CI) for normal pregnancies in the presence of a male fetus was 0.93 (range 0.88-1.03). This was significantly lower than that in the presence of a female fetus (median MoM=1.04). The gender difference was not observed in the Down syndrome pregnancies. The increased inhibin-A concentration would lead to a 2.3-fold higher false-positive rate in the presence of a female fetus (10.6% vs. 4.6%; p<0.05, Chi-square test). Because of the small number of cases studied, the results need to be substantiated by a larger series. If the gender effect is confirmed, adjustment for fetal sex may be necessary when inhibin-A is used as a screening marker.
authors.affiliation: Department of Obstetrics and Gynaecology, The University of Hong Kong, Tsan Yuk Hospital, Hong Kong, China. yhlam@hkucc.hku.hk
authors.forename: Y H
authors.initials: YH
authors.lastname: Lam
authors.forename: M H
authors.initials: MH
authors.lastname: Tang
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D004314:Down Syndrome / Q000097:blood; D005189:False Positive Reactions; D005260:Female; D005865:Gestational Age; D006801:Humans; D007265:Inhibins / Q000097:blood*; D008297:Male; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012016:Reference Values; D012189:Retrospective Studies; D012723:Sex
chemical_list: D015415:Biomarkers; D007265:Inhibins