Sex of babies determined by seasons, claims study
Couples can improve their chances of having a baby boy by conceiving in the autumn, while those who want a girl should try to conceive in spring, claims a study in the Human reproduction journal. Scientists from Modena in Italy believe that the reproductive system is trying to compensate for the higher incidence of male infant mortality - boys conceived in the autumn are born during warmer months, thus giving them a better chance of survival. Previous studies have also suggested that the evolutionary mechanism means that more male than female foetuses are produced. '[...]Nature recognising that male foetuses and newborns are more vulnerable than females, treats conception as a handicap race and tries to give boys a head start by favouring them in optimal reproductive conditions,' says Angelo Cagnacci, who headed the study. The team from Modena studied more than 14,000 births from the region over a six year period to see whether there was a significant difference in the sex ratio of babies born. They found that the most fertile months for conceiving a boy were from September to November, while the lowest fertile period was from March to May. The study revealed that some 535 males were conceived in autumn as opposed to 464 females. During the spring months, however, the ratio switched with only 487 males compared with 513 females. 'What is fascinating is the degree of disparity in the sex ratio, that the numbers of boys conceived compared with girls was so much higher in the favourable months when overall conception rates were high and so much lower in the unfavourable months when overall conception rates were low,' says Dr Cagnacci. However, despite abundant speculation, scientists have yet to explain how this sex selection occurs.