Female stress and birth seasonality in Tanzania

Abstract

Summary: Delivery records from Tanzanian hospitals reveal a marked seasonality of births in areas with holoendemic malaria. Accepted explanations of variations in conception rate are inadequate to account for these seasonal variations. The magnitude of the variation increases with higher parity but it has decreased over the past decade. The differences are related to different activity patterns of younger and older women, and to recent changes in the rural economy. Conception rate has a negative association with rainfall 4 months earlier; birth seasonality is therefore considered in relation to the agricultural cycle. While seasonal variations in sexual activity and pregnancy loss may be contributory factors, female stress due to the combination of malarial infection and physical exhaustion emerges as the major cause of seasonally depressed fecundity in areas with holoendemic malaria.