The incidence and outcomes of late-term pregnancy

Abstract Background: In low-risk women, it is being debated whether to induce labor at 41 weeks + 0 days or to allow the pregnancy to continue until 42 weeks + 0 days. Post-term pregnancy is linked to poor perinatal and maternal outcomes. However, little is known about the outcomes of late-term pregnancy. In this study, we aim to assess the incidence and adverse prenatal outcomes associated with late-term pregnancy.Methods: We retrospectively assessed all the singleton pregnant mothers who gave birth at Khaleej-e-Fars Hospital in Bandar Abbas, Iran, between January 2020-2022. All preterm and post-term deliveries were excluded. Mothers were divided into two groups: 1) late-term mothers and 2) term mothers. Term pregnancy was defined as 37 0/7 weeks to 40 6/7 weeks of gestation, and late-term pregnancy was defined as 41 0/7 weeks to 41 6/7 weeks of gestation. Demographic factors, obstetrical factors, maternal comorbidities, and prenatal outcomes were extracted from the electronic data of each mother. The incidence of late-term births was calculated. The Chi-square test was used to compare differences between the groups. Logistic regression models were used to assess the association of prenatal outcome with late-term pregnancy.Results: There were 8888 singleton deliveries during the study period. 1269 preterm and post-term pregnancies were ruled out. 309 (4.1%) of the 7619 deliveries were late-term, while 7310 (95.9%) were term. There were no sociodemographic differences between term and late-term mothers. The late-term group had a higher prevalence of primiparous mothers, and the term group had a higher prevalence of diabetes. Late-term mothers had a higher rate of macrosomia, meconium amniotic fluid, fetal distress, and a lower rate of LBW. After adjusting for confounders, late-term mothers had a higher risk of macrosomia aOR 2.24 (CI: 1.34-3.01), meconium amniotic fluid aOR 2.32 (CI: 1.59-3.14), and fetal distress aOR 2.38 (CI: 1.54-2.79). When compared to term pregnancy, the risk of LBW was lower in late-term pregnancy aOR 0.69 (CI: 0.36-0.81). Conclusions: Late-term pregnancy was found to be more likely to be associated with macrosomia, meconium amniotic fluid, and fetal distress, but serious maternal and neonatal adverse events were comparable to term pregnancy.