By Michael A. Thomas, MD

Professor, Reproductive Endocrinology and Infertility; Director, Division of Reproductive Endocrinology and Infertility, University of Cincinnati College of Medicine

Dr. Thomas reports he receives grant/research support from National Institutes of Health, Agile, and Therapeutics MD.

Synopsis: Couples attempting natural conception were found to have a lower chance of success per cycle when intercourse took place at or around the time of implantation.

Source: Steiner AZ, et al. Peri-implantation intercourse lowers fecundability. Fertil Steril 2014;102:178-182.

This is a secondary analysis of data obtained from two prospective time-to-pregnancy studies that were originally designed to determine the validity of antimullerian hormone (AMH) and follicle-stimulating hormone (FSH) as biomarkers of fertility in a community-based group of reproductive-aged women.1,2 Subjects were admitted to the original cohort if they were eumenorrheic and had been trying to conceive for ≤ 3 months or were about to make initial attempts at pregnancy. Participants also were instructed to use a daily study diary in which they documented acts of intercourse (IC), vaginal bleeding, medication use, and pregnancy test results. In the present study, 564 women, aged 30-44 years who were thought to be fertile, underwent analysis of a total of 1332 complete menstrual cycles. The investigators used the diary information to specifically observe IC frequency during the fertile window (5 days prior to and the day after ovulation) and continued through the time of implantation and for 2 or more days thereafter (5-9 days after ovulation). Subjects were grouped into the three categories related to the number of times that IC was recorded in their diaries during the pre-implantation time frame (0-9 days after ovulation) each cycle: 1) none, 2) one, and 3) two or more. The time of ovulation in all subjects was assumed to have occurred 14 days before the first day of the next menses. Data analysis was undertaken after adjusting for age, body mass index, menstrual cycle history, race, and previous pregnancy. Compared to women who did not have IC at and after the time of implantation, women who had IC during this period had a fecundability (chance of pregnancy per cycle) ratio of 0.65 (95% confidence interval, 0.42-0.91), indicating a decreased chance of conceiving. In addition, as IC frequency increased during this peri-implantation window, the probability of pregnancy decreased.

COMMENTARY

Previous investigators have noted that the best time to conceive, or the “fertile window,” is the time frame starting 5 days before and the day after ovulation in women undergoing attempts at conception.3 IC after this time will not result in a pregnancy. After ovulation, the oocyte is picked up by the fimbria, which are constantly sweeping over the ovary. If sperm is present once the oocyte makes its way to the ampullary portion of the tube, the oocyte has the chance of becoming fertilized, but this opportunity can only take place within 12 hours after this female gamete reaches the reproductive tract. If fertilized, the embryo has to traverse its way to the tubal ostia and now as a blastocyst implant into the endometrium by a series of steps that include endometrial receptivity and blastocyst invasion. Any disruption in this process will lead to a failure in implantation.

The goal of this study was to determine if IC in and around the time of implantation could impede endometrial receptivity, therefore decreasing the chance of pregnancy. It has been demonstrated that IC, with or without orgasm, can cause uterine contractions.4 However, it is unclear whether these contractions are able to either disrupt implantation, displace an implanted embryo, or possibly expel the embryo from the uterine cavity. In addition, we know that seminal fluid contains substances, including prostaglandins and growth factors (IL8, CXCL12, CCL2, soluble HLA-G, TGF-beta) capable of eliciting a strong maternal immune response. Intrauterine exposure can induce a proinflammatory reaction lasting up to 48 hours, which could also interfere with an embryo’s ability to stay in place.5 Because of these theoretical possibilities, this group of investigators decided to look at the effect of peri-implantation intercourse on conception.

Other research groups have been concerned about the role that stimulating uterine contractions can have on adversely affecting implantation. Uterine contractions have also been evaluated at the time of embryo transfer (ET) during an in vitro fertilization (IVF) cycle and were associated with poor implantation rates.6 Also, when atosiban, an oxytocin and vasopressin inhibitor, was given to inhibit contractility at the time of ET, implantation rates improved.7 Because of this, patients undergoing a fresh or frozen IVF cycle are routinely told to curtail vaginal IC until their first pregnancy test 2 weeks after ET. Avoidance of IC during this time period has been dogma at my institution since 1988. However, whether other methods of sexual expression (manual masturbation, oral stimulation, use of vibrators) that lead to orgasm and uterine contractions could produce a similar effect is less clear, and I know of no IVF centers that proscribe these activities.

Although this study demonstrated a reduction in the rate of pregnancy in couples engaging in vaginal IC around the time of implantation, the investigators noted limitations that may have impacted these results, such as the fact that subjects were predominately Caucasian (70-83%), diaries did not detail orgasm or barrier method use, and the periovulatory period was retrospectively assessed by menstrual cycle onset rather than by ovulation predictor kits, progesterone levels (to define an ovulatory cycle), or serial luteal phase hCG levels.

The results of this study confirm that IC at the time of the “fertile window” offers that best chance of conceiving. However, couples who are having trouble getting pregnant may need to better pinpoint the time of ovulation (using ovulation predictor kits or cervical mucus changes) and then avoid any form of female genital stimulation for a week or potentially negatively impact the chances of conception. As a fertility specialist, I routinely discuss every potential cause of a couple’s inability to achieve parenthood at the time of their first visit. Whether “abstinence in order to conceive” will be part of any future discussions will depend on larger multicenter studies that replicate these counterintuitive findings.

References