ABSTRACT
Our aim was to compare the fetal mortality rate (FMR), early neonatal mortality rate (ENMR) and perinatal mortality rate (PMR) of post-term and term births, 2) to examine trends in the incidence and perinatal mortality rates of post-term and term births. We used data from Spanish Perinatal Mortality Survey of 1980, 1986, 1989 and 1992. The data include 40,863 post-term births (42 weeks and over) and 517,060 term births (37-41 weeks). Perinatal mortality rates of post-term and term births were compared. The incidence of post-term births was 7.3%. The relative risk (RR) of FMR for post-term compared to term births was 1.1 (95% confidence interval [CI] 0.9-1.3), of ENMR was 1.6 (95% CI 1.4-2.0) and of PMR was 1.3 (95% CI 1.1-1.5). From 1980 to 1992 there was a significant reduction in the incidence of post-term births (8.1% vs 5.0%), in the FMR (4.5/1000 vs 1.9/1000), ENMR (4.3/1000 vs 2.0/1000) and PMR (8.7/1000 vs 3.9/1000) of post-term births. There was no significant difference in the FMR between post-term and term in each year studied. Post-term births had a significantly higher ENMR and PMR than term births in 1980, and they were equivalent from 1983 to 1992. The incidence of post-term births, its FMR, ENMR and PMR have been significantly reduced during the whole period studied.
