Baby-related old wives' tales can range from “chugging cough syrup will help you conceive,” to “adopt a baby, and you'll get pregnant.” Although ludicrous, pregnancy myths based on anecdotal evidence, limited scientific studies, or pure fiction continues to spread. Scientists at the Annual Meeting of the European Society of Human Reproduction and Embryology in Helsinki have dispelled another popular myth: “bed rest after sex increases your chances of getting pregnant.”

Previous research has found approximately 10 to 15 minutes of bed rest following intrauterine insemination (IUI) — a fertility treatment where a sample of sperm cells in fluid are injected directly into the uterus — can be beneficial on pregnancy rates. However, these results are based on just one cycle of treatment, and not the more real-world context of multiple cycles. Typically, women will often have a 10 to 20 percent chance of getting pregnant with just one IUI cycle. Those who undergo three to six cycles of IUI can boost their pregnancy rates as high as 80 percent.

Joukje van Rijswijk from the VU University Medical Center Amsterdam and her colleagues sought to conduct a larger study to put the popular myth to the test by randomly assigning 479 women receiving IUI to either 15 minutes of bed rest, or to get up and move around straight after treatment. The majority of the participants underwent several rounds of treatment, with a collective total of about 2,000 IUI cycles.

The findings revealed the old wives' tale made little difference to pregnancy rates, as women who got up immediately after IUI fared slightly better. The bed rest group had a pregnancy rate of 32.2 percent after lying down for 15 minutes, while those who stood up immediately had a rate of 40.3 percent. Although these differences are not statistically significant, they indicate there is no benefit from a brief period of bed rest after insemination.

"In our opinion," said van Rijswijk in a statement, "immobilization after IUI has no positive effect on pregnancy rates, and there is no reason why patients should stay immobilized after treatment."

Confusion of the female anatomy has led to the wide circulation of similar myths. Anatomical representations, such as in biology textbooks, show that the womb and the vagina are in a straight, vertical line. In reality, the vagina is tilted and the womb is then tilted relative to the vagina, fallopian tubes, and the ovaries, so it's not just one passage. Some women believe if they stand up after an IUI cycle everything is going to fall out, but anatomically, that is not plausible.

In addition, sperm cells can reach the fallopian tube five minutes after intravaginal insemination, and can survive in the womb for several days. This undermines the “lying still, feet-in-the-air” advice given those trying to conceive.

The researchers propose: "Why should bed rest affect that? There's no biological explanation for a positive effect of immobilization."

Van Rijswijk admits she doesn’t know if rest improves the chances of conceiving naturally because of a dearth of studies on the matter. However, it is known the pelvis does not move when the feet are up in the air. So any sperm that make it into the cervix will arrive regardless of whether you wait and rest following sex.

Ladies, there’s no reason to lie down post sex unless you need to rest for other reasons.

Source: Van Rijswijk J et al. Should patients be immobilised after intrauterine insemination? A randomised controlled comparison between 15 minutes of immobilization and direct mobilization. Annual Meeting of ESHRE Helsinki, FI. 2016.