title: Hour of birth as a prognostic factor for perinatal death.
abstract: The analysis of the 220,540 births and 2152 perinatal deaths recorded in Switzerland between 1979 and 1981 showed a variation of perinatal mortality rates (PMR) according to the hour of birth. The PMR for babies born between 4 pm and 2 am was 12 per 1000, contrasting with a figure of 8.4 per 1000 for babies born between 2 am and 4 pm. This pattern, which was fairly constant throughout the week, was characterised by a slow and steady increase from the very early morning, reaching a maximum in the late evening. There was also an hour-to-hour variation in the proportion of babies born weighing less than 2500 g, with a maximum in the evening and a less pronounced peak in the morning: the mortality rates by birthweight were raised only in the evening. Since the availability of hospital staff and equipment also follows a circadian rhythm, the variation in PMR may be related to a circadian rhythm of quality of care or possibly to chronobiological or selection factors.
mesh_terms: D000704:Analysis of Variance; D001724:Birth Weight; D036861:Delivery, Obstetric; D005260:Female; D006801:Humans; D007226:Infant Mortality; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008423:Maternal Age; D010500:Perinatology / Q000592:standards; D011379:Prognosis; D011787:Quality of Health Care; D013557:Switzerland; D013995:Time; D013997:Time Factors