P-441 Frequency of sexual intercourse and fecundability among women trying to conceive in Japan
Authors: Maeda E , Akizuki Y , Fujishima A , Nomura K , Arata N 
Published: June 2023

Study question

To what extent is the frequency of sexual intercourse associated with fecundability?

Summary answer

Frequency of sexual intercourse was the most influential factor in achieving pregnancy but was low among women trying to conceive in Japan.

What is known already

The Japanese National Fertility Survey showed that 39% of married couples had experienced some fertility problems. A recent national survey revealed that 47% of married couples were sexless. The effect of intercourse frequency on time-to-pregnancy (TTP) has not been well investigated in Japan despite the high prevalence of fertility problems and sexless marriages.

Study design, size, duration

We used a social research panel in Japan to conduct an internet-based preconception cohort study of pregnancy planners who were not undergoing fertility treatment. In total, 3,796 women were enrolled in February 2021 and followed up for six months. We used data from 2,371 (62%) participants who discontinued contraception.

Participants/materials, setting, methods

Participants were married women between the ages of 25 and 39 who planned to conceive within a year but were not pregnant at the time of enrolment. Those receiving fertility treatment or trying to conceive for more than six months were excluded from the recruitment. Participants reported frequency and timing of intercourse along with sociodemographic and lifestyle factors. TTP was measured in months, and discrete-time Cox regression was used to estimate fecundability odds ratios (FORs).

Main results and the role of chance

Of the 2,371 women, 31% had intercourse “less than once in a few months” (hereafter, the Lowest Frequency), 54% had intercourse “several times per month” (hereafter, the Middle Frequency), and 15% engaged in intercourse “several times or more per week” (hereafter, the Highest Frequency). Higher frequency groups were younger, were married for a shorter period, and were less likely to have kids (all Ps for trend&lt;0.05). Adjusted FORs of the Middle and the Highest Frequency groups were 2.20 (95% confidence interval [CI]: 1.56—3.10) and 3.41 (95% CI:2.29—5.08), respectively, resulting in a shorter TTP compared to the Lowest Frequency group. Covariates showing significant associations with fecundability were timed intercourse of fertile window (adjusted FOR=1.76, 95% CI: 1.37—2.27), folic acid and/or multivitamin use (adjusted FOR=1.44, 95%CI: 1.12—1.84), and participant age (adjusted FOR=0.96, 95% CI: 0.92—0.99), whereas the other variables, such as partner age, sociodemographic factors, health indicators (e.g., body mass index, cycle regularity), or lifestyles (e.g., smoking, physical activity), did not show significant associations.

Limitations, reasons for caution

Intention to conceive could be a confounder, although we used timed intercourse as a proxy measure. Misclassification may have occurred due to self-reported information.

Wider implications of the findings

Occasional intercourse among pregnancy planners might be linked to the high prevalence of infertility in Japan through a direct reduction in fecundability before the age-related fertility decline. Informing couples about the frequency of intercourse and TTP might help them achieve pregnancy earlier.

Trial registration number

NA