Fertility has declined in most industrialised countries. While the causes are largely unknown, a number of factors may contribute to declining fertility rates, including the age a person starts a family, their diet, whether they smoke or drink alcohol, their weight, and whether they exercise. But whatever the causes, this decline in fertility means that about 15% of couples now take more than one year to conceive.
While much is still unknown about declines in fertility, our team wanted to understand the relationship between low fertility and health. We used the time to pregnancy (the number of months it takes to conceive) as an indirect measure of fertility. We found that a longer time to pregnancy was linked to more hospitalisations for both men and women and to a shorter lifespan for women. This was particularly true when it took longer than 18 months to conceive.
To conduct our study, we used data on participants of two surveys of twins – totalling approximately…