Association between human chorionic gonadotropin (hCG) levels and adverse pregnancy outcomes: A systematic review and meta-analysis.

Human chorionic gonadotropin (hCG), a glycoprotein produced in the placenta, is crucial for a healthy pregnancy. We investigated the relationship between hCG levels and adverse pregnancy outcomes. We conducted a systematic review including studies measuring hCG blood levels in the first or second trimester, reporting on any of the 12 predefined adverse pregnancy outcomes with logistic regression-adjusted association estimates. The primary outcomes were placenta-associated complications, such as miscarriage, preeclampsia, intrauterine growth restriction, and preterm delivery. We searched PubMed, Embase and CINAHL Complete. The hCG levels were analysed as multiple of the median (MoM). Odds ratio (OR) and 95% confidence interval (CI) were used. Risk of bias and the certainty of evidence were assessed using ROBINS-I and GRADE, respectively. Meta-analysis also showed that hCG levels, reported as MoM ≥2/2.31/2.5, might be associated with an increased risk of preeclampsia (OR 2.08, 95% CI 1.26 to 3.44) and preterm delivery (OR 1.29, 95% CI 1.12 to 1.47), but the evidence is very uncertain. High second trimester hCG levels may be associated with preeclampsia and preterm delivery but confidence in evidence is low.