Weight gain between first and second pregnancies associated with increased odds of male second child

A slightly greater number of males than females are born worldwide every year. In recent decades, although there are still more baby boys born than girls, there has been an apparent decline in the ratio of male to female newborns in several industrialized countries, including Canada, Denmark, England, Germany, Japan and the United States. That has led researchers to ask: Are there any factors that can influence the probability of giving birth to a baby boy or girl?