Introduction
Most couples have life plans that include children, as parenthood is one of the most universally desired aims in adulthood. However, not all couples can achieve their desires, and a proportion of them will need medical help to solve reproductive issues. A remarkable demographic shift in recent years has affected female fecundity, including delayed childbearing age and changing lifestyles.(1) Estimating population-based fecundity is important for policy improvement in healthcare as these changes occur.
According to the International Committee for Monitoring Assisted Reproductive Technology and the World Health Organization, infertility is a disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse.(2) Previous studies have reported the prevalence of infertility among different populations in China (15.5% in women attempting to conceive and 24.9% in women at risk for pregnancy) using the common definition of failure to conceive within the last 12 months.(3) Time to pregnancy (TTP), which is measured as the months or menstrual cycles from attempting to conceive until successful pregnancy, is gaining more attention as another measure of subfecundity or infertility.(4) In addition to estimating the cumulative probabilities of conception to prevent variation across different definitions and study designs,(5) this indicator can find suitable thresholds to determine the grades of subfertility and is more convenient to measure the distribution of epidemiology and the study mechanism of the biological process.(6, 7)
Using TTP as a continuous indicator to estimate the likelihood of conception during a certain time, this study aimed to portray the fecundity of couples in a representative cross-sectional population of reproductive ages in China.
Materials and Methods