Perinatal Mortality Rate in Weekend Birth in Japan

Background: It was unknown whether risk of perinatal mortality rate (PMR) was higher in weekend than week days births in Japan and how Japanese obstetricians attempted to reduce numbers of weekend births. Methods and Findings: Retrospective observational study on 301510 women registered in the Japan Society of Obstetrics and Gynecology registry system who gave birth to singleton infants at gestational week ≥ 22 between 2005 and 2009. The proportion of women giving birth vaginally vs. by caesarean section with and without uterotonics was determined according to day of the week. Perinatal mortality included stillbirth and early neonatal death within one week after live birth occurring on and after gestational week 22. The PMR was similar between weekdays and weekend births (2.0% [4898/240455] vs. 2.0% [1217/61055], respectively). The fractions of Sunday and Thursday births were smallest and largest, respective; the mean ± SD fractions of Saturday and Sunday births were 10.4 ± 0.2% and 9.9 ± 0.3%, respectively, while those of Monday, Tuesday, Wednesday, Thursday, and Friday births were 14.6 ± 0.3%, 16.5 ± 0.2%, 15.9% ± 0.4%, 17.1% ± 0.4%, and 15.6% ± 0.3% of all 301510 births, respectively. The numbers of vaginal births with uterotonics and of caesarean births per day were approximately double and ~3.6-fold greater for weekdays than for those for weekend, respectively. Conclusions: The PMR did not differ between births that occurred on weekdays and weekend. Frequent uterotonic use and caesarean delivery on weekdays explained the disproportionately reduced number of weekend births.