Objective To investigate the relative contribution of genetic and environmental components
to subfertility. Design Twin design using a quantitative genetic liability threshold model that …

In modern societies, individual differences in completed fertility are linked with genotypic
differences between individuals. Explaining the heritability of completed fertility has been …

We used a set of bivariate biometrical models to define a “competition” between the
biological domain and the psychological domain to account for genetic variance measured …

Background. Numerous rare genetic conditions are known to influence fecundability in both
males and females. It is less clear to what extent more subtle genetic differences influence …

Miscarriage is the most common type of pregnancy loss, occurring in up to 15% of clinically
recognized pregnancies. Our understanding of the etiology is still limited but is believed to …

BACKGROUND We have previously observed that an increasing time to pregnancy (TTP) is
associated with a reduced frequency of twin deliveries in couples not receiving infertility …

Background: Trends in biologic fertility are elusive. Possible negative trends in male
reproductive health are still debated, and their effect on human fertility might be negligible …

Female fertility is a complex trait with age-specific changes in spontaneous dizygotic (DZ)
twinning and fertility. To elucidate factors regulating female fertility and infertility, we …

BACKGROUND. Decreased fecundity has been hypothesized as one of the causes of the
widespread decline in twin rates in the 1960s and 1970s. The association between high …

BACKGROUND: A previous European study found a longer time to pregnancy (TTP) among
fertile women from Paris compared with women from other Western European countries. A …