News

30th April 2004

Summer-born mothers have fewer babies, say researchers

Girls who are born during the summer months grow up to have fewer children than those born at other times of the year, say researchers from Austria in a study published in the European journal Human Reproduction.

Dr Susanne Huber, from the University of Veterinary Medicine in Vienna, and her colleagues from the University of Vienna, studied more than 3000 Austrian women over 45 who were on a national database, and found that, on average, those born in July had 0.3 less children than those born in December.

However, although summer-born mothers tend to have fewer children than women born during the autumn, winter or spring, the findings showed no association between birth month and childnessness.

Dr Huber and her team also found that their results reflected past trends, showing a similar pattern to a study of pre-modern women living in Canada, as well as a historical study of Dutch women. This supports the researchers' findings and suggests that, despite the degree of choice available to modern women due to lifestyle and contraceptive options, the birth month is a significant factor affecting levels of reproduction.

An earlier study of Austrian men by the same researchers found that the average number of children fathered was highest among men born in the spring and lowest among those born in the winter. 'This may indicate that males and females might respond differently to the season of birth,' said Dr Huber.

Dr Huber said that there could be many possible causes for the association between birth month and reproduction, including environmental variations - such as temperature, light levels and nutrition - at different times of the year. It is possible that conditions experienced in the womb and as a newborn differ according to the season, which may have an effect on the baby's early development and future fecundity. She concluded that there could be other factors that might also play a role and said that further research is needed.

• Researchers have also recently suggested that the time of year your baby was born can influence her character? Find out more
• Do you believe the season of birth has affected you or your baby in any way? Have your say