Accuracy of serum human chorionic gonadotrophin for estimating gestational age in the first trimester of pregnancy: population-based study

This study determined the accuracy of first trimester serum Human Chorionic Gonadotrophin (HCG) for estimating gestational age (GA). We included 273,584 singleton livebirths that had a first trimester ultrasound and measured serum HCG at 4-12 weeks gestation in XXX from 2012−2018. We estimated HCG accuracy compared to known GA, within a boundary of +/- 1 week. Between 4−8 weeks gestation, sensitivity of HCG was over 88%, and specificity over 51%. However, at 9−12 weeks, sensitivity declined from 72% to 0%, and specificity rose from 86% to 100%. At all GA, the Positive Predictive Value was consistently under 42%, while Negative Predictive Values were over 96%. Within epidemiological studies in which GA is otherwise unknown, first trimester serum HCG may aid somewhat in estimating GA between 4 to 6 weeks gestation, but much less so thereafter. Thus, there remains an ongoing need for an accurate method for estimating missing GA within large datasets.