Sex ratios at birth and environmental temperatures

The relationship between average monthly air temperature and sex ratios at birth (SRB) was analyzed for children born in Germany during the period 194 6-1995. Both the absolute temperature and - more markedly - the monthly tem perature deviations from the overall mean were significantly positively cor related with the SRB (P<0.01) when temperatures were time-lagged against th e SRB data by -10 or -11 months. It is concluded that the sex of the offspr ing is partially determined by environmental temperatures prior to concepti on.