Biological Anthropology Section
Volunteered - Oral Presentation Session
The total fertility rate of Japanese women is below population replacement level. Recent research revealed that Japanese married couples have low coital frequency, and high rates of infertility treatment; however it is not known if these two findings are related. The present study examined coital frequency, infertility treatment, and probability of conception (fecundability) in a prospective study. Japanese women aged 23-34 years without a history of infertility who wanted to conceive their first child were recruited on-line. An initial survey asked about coital frequency and menstrual cycle status in the previous three months. During 24 weeks of follow-up participants prospectively recorded menstrual bleeding, sexual intercourse, ovulation, and pregnancy. Final surveys on pregnancy and infertility treatment were collected one year after intake. Cox regression analysis was used to estimate hazard ratios (HR) of conception across 24 weeks. A logistic regression was used to estimate odds ratios (OR) of initiating infertility treatment within one year of follow-up. Among 76 participants completing follow-up, 35 (46%) spontaneously conceived in 24 weeks, and 36 (47%) initiated infertility treatment by the end of one-year follow-up. Coital frequency reported at intake (and also during the 24 weeks follow-up) was significantly positively associated with natural conception (HR 1.11, 95%CI 1.02, 1.23). Women with higher sexual frequency at intake were less likely to initiate infertility treatment within one year of follow-up (OR 0.97, 95%CI 0.94, 1.00), supporting that low coital frequency among Japanese women wanting to conceive for the first time is related to subsequent adoption of infertility treatment.