Perinatal Morbidity and Mortality in Late-term and Post-term Pregnancy. NEOSANO Perinatal Network's Experience in Mexico

Objective: The objective of this study is to identify adverse perinatal outcomes associated with pregnancies at or beyond 40 weeks.

Study Design: Retrospective cohort study conducted in Mexico, with information obtained from the NEOSANO's Perinatal Network Database from April 2006 to April 2009. Multiple births, babies with inaccurate gestational age or babies with congenital malformations were excluded. Logistic regression models were used to analyze perinatal complications associated with pregnancies ≥ 40 weeks.

Result: A total of 21 275 babies were analyzed; of these, 4545 (21.3%) were of 40 to 40[frac67] weeks, 3024 (14.2%) 41 to 41[frac67] weeks and 388 (1.8%) 42 to 44 weeks of gestation. Adverse perinatal outcomes associated with 40 to 40[frac67] weeks deliveries were (odds ratio; 95% confidence interval): macrosomia (1.9; 1.5 to 2.6), acute fetal distress (1.4; 1.2 to 1.7), emergency cesarean delivery (1.4; 1.2 to 1.5) and chorioamnionitis (1.4; 1.2 to 1.6). Adverse perinatal outcomes associated with 41 to 41[frac67] weeks were macrosomia (2.5; 1.8 to 3.3), chorioamnionitis (2; 1.7 to 2.3), emergency cesarean delivery (1.8; 1.6 to 2.1) and acute fetal distress (1.4; 1.1 to 1.7). Adverse perinatal outcomes associated with 42 to 44 weeks were macrosomia (7; 4.6 to 10.7), meconium aspiration syndrome (5.6; 2.8 to 11.2), neonatal death (4.8; 1.7 to 13.8), stillbirth (4.3; 1.4 to 13.5), 5' Apgar <4 (4.2; 1.1 to 15.7), chorioamnionitis (2.8; 2.2 to 3.9), admission to neonatal intensive care unit (2.7; 1.5 to 4.8), admission to neonatal intensive care unit or step-down unit (2.4; 1.5 to 3.9), acute fetal distress (1.8; 1.2 to 2.6) and emergency cesarean delivery (1.8; 1.3 to 2.4).

Conclusion: An increased risk for perinatal and maternal complications were detected as early as 40 weeks' gestation. The risks of stillbirth and neonatal death were significantly higher in the post-term group than the control group.