Effect of Fetal Gender and Sex on Maternal hCG Levels

Does a pregnancy test become positive later when the fetus is a boy, and does it become positive earlier when the fetus is a girl?

In this study published by Yaron Y et al in Human Reproduction the authors studied 1,325 pregnant women with singleton pregnancies at 10-13 weeks.and compared different hormone levels including the pregnancy hormone hCG human chorionic gonadotropin between women carrying a male and a female fetus  They found that women who had a female fetus had hCG levels significantly higher than women who carried a male fetus. This finding is consistent with that found by several other researchers.

These findings may have implications not only on evaluating risks of Down syndrome (women carrying female fetuses had a higher risk for Down syndrome), but also on timing of a pregnancy test. If women carrying a male fetus have lower hCG levels then it may be possible that their first positive urine pregnancy test could be delayed because of the male gender.