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. In a 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  

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.