Early vaginal bleeding and first-trimester markers for Down syndrome

Objectives: To assess the effect of early vaginal bleeding on first-trimester markers for Down syndrome. Methods: A retrospective study was conducted on 2330 normal singleton fetuses who underwent first-trimester combined screening for Down syndrome based on ultrasound and maternal serum markers. Fetal nuchal translucency (NT), maternal serum pregnancy-associated plasma protein A (PAPP-A), free β-hCG and the false-positive rate of the test were compared between pregnancies with (n = 253) and without (n = 2077) a history of early vaginal bleeding. Results: The mean ± SD log₁₀ MoM for NT, PAPP-A and free β-hCG was -0.024 ± 0.101, 0.007 ± 0.244, 0.047 ± 0.273 and -0.011 ± 0.108, -0.006 ± 0.223, 0.008 ± 0.264 in pregnancies with and without a history of early vaginal bleeding, with a p value of 0.07, 0.40 and 0.03 respectively. The false-positive rate was 2.4% and 3.6% (p = 0.33). Conclusions: An earlier episode of vaginal bleeding is associated with an increase in maternal serum free β-hCG levels at first-trimester combined screening for Down syndrome. However, this phenomenon is unlikely to significantly affect the false-positive rate of the test.