Researchers based at the University of Utah used the Utah Population Database – an enormous comprehensive historical record of population data from the state of Utah – to examine whether bearing non-identical twins had any effect on mothers’ overall health and fertility. A tendency to bear non-identical twins often runs in the family, and initially scientists had postulated that this might have detrimental effects on women due to the increased costs of bearing and looking after twins.
However, the data showed that the mothers of twins tended to live longer post-menopause and had smaller intervals between the birth of their children, generally appearing to be more fertile. While previous studies have hinted that this might be the case, this is the first study to take place on such a large scale – the researchers analysed historical information from more than 58,000 women, including more than 4,500 mothers of twins. The authors suggest that “women who continue to bear offspring to older ages are a more robust subset who have higher fertility and are more likely to successfully incur the cost of twins”.