Browsing by Author "Kalema, Terhi"

The aim of this case-control study was to study risk factors for post-term pregnancies (≥ 42 gestational weeks) in a Finnish material consisting of women having given birth 1.9.2005 – 31.12.2008 at Jorvi Hospital, Kätilöopisto Maternity Hospital and Women's Hospital. There were 48108 deliveries, and the prevalence of post-term pregnancies was 6.6 %. After exclusion of preterm births, twins and triplets, electively sectioned and induced labors, the number of deliveries was 33779, out of which 1121 were post-term (cases). There were 32658 newborns between 37+0 and 41+6 gestational weeks, and a control group twice as large as the case group was randomly selected (controls, n=2242). Differences between cases and controls were assessed using Mann-Whitney U-test (continuous variables) and Chi-square (dichotomous or categorical variables). Multivariate analysis and adjustment for potential confounding variables were performed using binary unconditional logistic regression. Cases and controls did not differ with respect to maternal age, but BMI of the cases was significantly higher than controls, and they smoked less during pregnancy. There were also more primigravidas among cases than among controls. Cases had significantly more antenatal visits during pregnancy when compared to controls. After adjustment for confounders, significant risk factors for post-term pregnancy were primiparity, increasing maternal BMI, obesity and not living in cohabitation. Smoking, maternal age or first trimester ultrasonography did not significantly affect the risk. Women with pathological glucose tolerance test had smaller risk for post-term pregnancy. Women with post-term pregnancies had higher risk for primary inadequate contractions of the uterus and secondary uterine inertia. The results add to the growing literature that risk factors for post-term pregnancy are primiparity, not cohabitating and obesity, whereas gestational diabetes was a protective factor. In this study, maternal age, first trimester ultrasound or smoking had no significant effect on the risk.