Objective To examine whether the perinatal mortality of infants born during holidays differs from that of infants born on workdays, and to elucidate its cause.
Design Cross-sectional study.
Setting Vital statistics linked to the National Infant Mortality Survey data for 1999 births in Korea.
Population In all, 628 485 births in 1999 in Korea.
Methods Number of births and perinatal mortality were classified according to the day of the week using the occurrence index. After adjusting for confounding factors, the odds ratios (ORs) for increased holiday mortality were estimated using logistic regression.
Main outcome measure Birthweight-adjusted perinatal mortality.
Results Births on holidays were 33% fewer and perinatal deaths 24% higher than expected (PMR, Perinatal Mortality Rate, 16.4 versus 12.8; OR, 1.3; 95% CI, 1.2–1.4). After the adjustment of birthweight, gender, plurality and congenital anomalies, the odds ratio for death of infants born during holidays was 1.2 (95% CI, 1.1–1.3).
Conclusions The higher perinatal mortality during holidays in Korea appears to be due to different qualities of perinatal care, rather than difference in case-mix.