Premium
The pattern of maternal serum inhibin‐A concentrations in the second trimester of pregnancy
Author(s) -
Watt H. C.,
Wald N. J.,
Huttly W. J.
Publication year - 1998
Publication title -
prenatal diagnosis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.956
H-Index - 97
eISSN - 1097-0223
pISSN - 0197-3851
DOI - 10.1002/(sici)1097-0223(199808)18:8<846::aid-pd354>3.0.co;2-p
Subject(s) - pregnancy , medicine , gestational age , second trimester , gestation , obstetrics , gynecology , biology , genetics
Maternal serum inhibin‐A concentration is a useful marker in prenatal screening for Down syndrome in the second trimester. We measured inhibin‐A concentrations in 4304 pregnancies without Down syndrome between 14 and 22 weeks of pregnancy to determine the median values according to gestational age. There was a U‐shaped pattern of inhibin‐A concentration against gestational age with a minimum concentration at 17 weeks and 1 day (120 days). We suggest that screening centres use a quadratic equation when estimating their normal median inhibin‐A level, constraining the shape of the curve and fixing the lower point of the curve to occur at 120 days, but allowing its position in relation to the vertical inhibin‐A axis to be set according to the local data. This approach will systematically allow for the changing inhibin‐A concentration without introducing the instability of deriving a fresh quadratic equation for each screening centre and each time a centre's medians are revised. © 1998 John Wiley & Sons, Ltd.