ABSTRACT
OBJECTIVE: To investigate whether the ratio of fetal cells in the maternal circulation differs before and after the blood passes through the maternal lung. METHODS: We performed polymerase chain reaction-based Y-sequence analysis of DNA derived from antecubital vein blood obtained before and 2 hours after cesarean delivery, and from uterine vein blood obtained during cesarean of 14 women carrying male fetuses. RESULTS: Fetal DNA was detected in 17 tested specimens and, as estimated by comparison with parallel dilution series, the fetal-maternal DNA ratio was 1:10(5) to 1:10(6). However, there was no significant difference in the amount of Y-chromosomal DNA detectable between uterine vein blood and peripheral blood after polymerase chain reaction and Southern hybridization. In DNA derived from peripheral blood after delivery, the intensity of Y-specific fetal DNA sequences was also not significantly increased. CONCLUSION: Our results argue against the often-stated hypothesis of different ratios of fetal to maternal DNA in the uterine vein versus peripheral blood, and indicate that even delivery does not seem to increase the flow of fetal cells into the maternal circulation.