BACKGROUND:Climate vulnerability of the unborn can contribute to adverse birth outcomes, in particular, but it is still not well understood. We investigated the association between ambient temperature and stillbirth risk among a historical population in northern Sweden (1880-1950). METHODS:We used digitized parish records and daily temperature data from the study region covering coastal and inland communities some 600 km north of Stockholm, Sweden. The data included 141,880 births, and 3,217 stillbirths, corresponding to a stillbirth rate of 22.7 (1880-1950). The association between lagged temperature (0-7 days before birth) and stillbirths was estimated using a time-stratified case-crossover design. Incidence risk ratios (IRR) with 95% confidence intervals were computed, and stratified by season and sex. RESULTS:We observed that the stillbirth risk increased both at low and high temperatures during the extended summer season (April to September), at -10°C, and the IRR was 2.3 (CI 1.28, 4.00) compared to the minimum mortality temperature of +15°C. No clear effect of temperature during the extended winter season (October to March) was found. Climate vulnerability was greater among the male fetus compared to the female counterparts. CONCLUSION:In this subarctic setting before and during industrialization, both heat and cold during the warmer season increased the stillbirth risk. Urbanization and socio-economic development might have contributed to an uneven decline in climate vulnerability of the unborn.

BACKGROUND:Intrapartum fever is a well-known risk factor for adverse perinatal outcomes. Maternal intrapartum fever ≥39.0°C at term is a rare event during labor, and there is scarce evidence regarding its implications. OBJECTIVES:To investigate the association between very high intrapartum maternal fever and perinatal outcomes in term pregnancies. METHODS:A retrospective cohort analysis including 43,560 term, singleton live births in two medical centers between the years 2003 and 2011 was performed. We compared parturients who experienced a maximal intrapartum fever of <38.0°C with two subgroups of parturients who experienced respective maximal fevers of 38.0-38.9°C and ≥39°C. Adjusted risks for adverse perinatal outcomes were calculated by using multiple logistic regression models to control for confounders. RESULTS:Compared with normal intrapartum temperature, intrapartum fever ≥39.0°C was associated with an extremely elevated risk for neonatal sepsis 16.08 (95% CI: 2.15, 120.3) as well as with low Apgar scores and neonatal intensive care unit admissions (p < 0.001). Additionally, very high intrapartum fever was related to significantly higher risk for operative delivery (p < 0.001). CONCLUSIONS:Extremely elevated intrapartum fever is an important indicator of severe neonatal morbidity and operative delivery.