Patrones horarios de los partos en la Casa de Maternidad de Madrid (1887-1914).

The group of primates to which our species belongs is generally active during the daytime, so deliveries start during the night and conclude in the early hours of the morning. Preserving a night-time delivery must have been very important for the survival of our ancestors from Homo erectus, 1.8 million years ago, onwards, as the intense foetal encephalization experienced by this species gradually complicated delivery, as it combined with a narrower pelvis, a consequence of bipedalism, adopted millions of years before. The oldest research into delivery time patterns is limited to hospital records from the 1930s and 1940s, before extensive medicalisation of delivery became institutionalised, and it describes a generally nocturnal pattern. The present study analyses time patterns of deliveries in two much earlier populations, from the late 19th and early 20th centuries, a total of 21,340 births in 27 years. They correspond to the Casa de la Maternidad, a charity institution initially linked to the foundling hospital in the capital, but which gradually became --during the first half of the 20th century-- the main maternity hospital in the city. The results confirm the preservation of an ancestral circadian pattern of delivery, predominantly nocturnal and in the early hours of the morning. [ABSTRACT FROM AUTHOR]