Peri-implantation Intercourse Does not Lower Fecundability

Joseph B. Stanford; Jared L. Hansen; Sydney K. Willis; Nan Hu; Alun Thomas


Hum Reprod. 2020;35(9):2107-2112. 

In This Article

Abstract and Introduction


Study Question: Does sexual intercourse in the implantation time window (5–9 days after ovulation) reduce fecundability?

Summary Answer: After adjustment for intercourse in the fecund window and clustering by couple, there was no association between intercourse in the implantation time window and fecundity.

What is Known Already: Previous research has suggested an association between intercourse in the peri-implantation time window (5–9 days after estimated ovulation) and reduced fecundability.

Study Design, Size, Duration: We used data from the FERTILI study, a prospective observational study conducted in five European countries, with data collected from 1992 to 1996.

Participants/Materials, Setting, Methods: Women who were experienced in fertility awareness tracking kept a daily diary of cervical mucus observations, basal body temperature measurements, coitus and clinically identified pregnancy. We estimated the day of ovulation as cycle length minus 13 days. From 661 women, 2606 cycles had intercourse during the fecund window (from 5 days before to 3 days after the estimated day of ovulation), resulting in 418 pregnancies (conception cycles). An established Bayesian fecundability model was used to estimate the fecundability ratio (FR) of peri-implantation intercourse on fecundability, while adjusting for each partner's age, prior pregnancy, the couple's probability of conception and intercourse pattern(s). We conducted sensitivity analyses estimating ovulation as cycle length minus 12 days, or alternatively, as the peak day of estrogenic cervical mucus.

Main Results and the Role of Chance: There was no effect of peri-implantation intercourse on fecundability: adjusted FR for three or more acts of peri-implantation intercourse versus none: 1.00, 95% credible interval: 0.76–1.13. Results were essentially the same with sensitivity analyses. There was an inverse relationship between frequency of intercourse in the fecund window and intercourse in the peri-implantation window.

Limitations, Reasons for Caution: Women with known subfertility were excluded from this study. Many couples in the study were avoiding pregnancy during much of the study, so 61% of otherwise eligible cycles in the database were not at meaningful risk of pregnancy and did not contribute to the analysis. Some couples may not have recorded all intercourse.

Wider Implications of the Findings: We believe the current balance of evidence does not support a recommendation for avoiding intercourse in the peri-implantation period among couples trying to conceive.

Study Funding/Competing Interest(S): No external funding. The authors have no potential competing interests.

Trial Registration Number: N/A.


Fecundability is the probability of a clinical pregnancy occurring in a given menstrual cycle. It is a function of reproductive biology (the potential of the couple to produce offspring) and intercourse in the fecund window (the days prior to and the day of ovulation during which conception is possible) (Barrett and Marshall, 1969; Wilcox et al., 1995; Colombo and Masarotto, 2000). A variety of characteristics of women and men are related to fecundability including age, prior pregnancies and history of menstrual irregularities (Wood, 1994). Understanding the determinants of fecundability is of interest to clinicians in the field of reproductive health, and to couples who are attempting to conceive (Stanford, 2015).

Implantation is a pivotal moment in the establishment of clinical pregnancy. Implantation is recognized to occur in humans approximately 5–9 days after ovulation (Wilcox et al., 1999). This time period is called the peri-implantation window. Exposures that impact the endometrial and intrauterine environment during this time frame could reduce the probability of implantation through various mechanisms, including induction of myometrial contractions, or changes in immune or inflammatory processes of endometrial maturation during the luteal phase (Fox et al., 1970; Fanchin et al., 1998; Shafik et al., 2005).

In a prospective cohort study, Steiner et al (2014) studied 564 women without infertility between 30 and 44 years of age who were seeking pregnancy. They found that two or more days of sexual intercourse during the peri-implantation window was associated with lower incidence of clinical pregnancy, when compared with 0 days: fecundability ratio (FR) of 0.62; 95% credible interval, 0.42–0.91. The authors suggested that orgasm induced myometrial (uterine) contractions at the time of expected implantation, or asynchronous immune or inflammatory responses to seminal fluid may reduce the incidence of clinical pregnancy in cycles with a higher frequency of peri-implantation intercourse. If this finding is replicated and confirmed, couples seeking to conceive should be advised to reduce or avoid intercourse in the peri-implantation period. We sought to replicate this finding in a dataset from a different prospective cohort study.