Location of the placenta or the umbilical cord insertion site in the lowest uterine segment is associated with low maternal blood pressure

Objective To evaluate whether placental abnormalities and umbilical cord insertion site affect the occurrence of pre-eclampsia and maternal blood pressure. Design Case-control study. Setting Showa University Hospital, Tokyo, Japan. Population A total of 5722 consecutive women who delivered singleton infants were included in the study. Methods The associations of placental abnormalities, the location of the placenta, the location of the cord insertion site, and maternal background with the occurrence of pre-eclampsia and maternal blood pressure at the term of pregnancy were analysed. Main outcome measure Pre-eclampsia and maternal blood pressure at the term of pregnancy. Results Pre-eclampsia was observed in 236 women (4.1%). Pre-eclampsia was frequently observed in women with placental form abnormalities (odds ratio 3.0) and infarction of the placenta (odds ratio 5.3). Pre-eclampsia was observed in 0 and 4.1% of women with and without placenta praevia, respectively (P = 0.004), and in 0 and 2.5% of women with and without low cord insertion during the first trimester, respectively (P = 0.018). After adjustment for confounding variables, the multivariate regression analyses revealed reductions of 8.4 and 5.0 mmHg in systolic and diastolic blood pressure, respectively, in women with placenta praevia compared with women without placenta praevia, and reductions of 4.3 and 3.1 mmHg in systolic and diastolic blood pressure, respectively, in women with low cord insertion during the first trimester compared with women without low cord insertion. Conclusion Not only placenta praevia but also low cord insertion are associated with low frequencies of pre-eclampsia and low maternal blood pressure.