Lying on your back after sex might improve your chances of getting pregnant. While there’s no research specifically on lying still after sex to back up the claim, there is research on the fertility treatment IUI being more effective if the woman remains on her back for some time.
With IUI, specially washed sperm are transferred directly to the woman’s uterus via the cervix, through a thin catheter. In one study, researchers wanted to know if IUI treatment would be more effective if the woman remained on her back for 15 minutes after the procedure.
Researchers found that the women who remained on their backs for 15 minutes after the sperm transfer had a 27% pregnancy rate after three cycles, while the women who were encouraged to get up right after the treatment had an 18% pregnancy rate after three cycles. Remaining horizontal did improve pregnancy rates.
These results were actually surprising to the researchers, because previous research implied that sperm are fast swimmers. Studies on how quickly the sperm travel from the cervix up to the fallopian tubes (where they hope to meet an egg) found that it takes anywhere from two to ten minutes.
Based on how fast the little guys can swim, and the fact that they’ll swim up with or without the help of gravity, you’d think that lying still those 15 minutes wouldn’t make much of a difference. But this study implies it can make some.
The Bottom Line
If lying still on your back after IUI may improve your chances, and in that case the sperm are getting a helpful push ahead into the uterus, then perhaps lying still for 15 minutes after sex can help too.
That being said, you shouldn’t stress over it. The research was on IUI, not sex, and for all we know, lying on your back after sex may not make a true difference.
If you do want to try lying on your back afterward, there’s no need to remain horizontal for more than 15 minutes, and you don’t need to try anything nutty like standing on your head. It sounds funny, but you're not alone if you've thought of it.
And if you need to use the bathroom right after sex, get up and go ahead. You’re not going to ruin your chances for a positive if you do. You can reassure yourself by remembering that women in the research group who got up right away still got positive pregnancy results.
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Custers IM, Flierman PA, Maas P, Cox T, Van Dessel TJ, Gerards MH, Mochtar MH, Janssen CA, van der Veen F, Mol BW. “Immobilisation versus immediate mobilisation after intrauterine insemination: randomised controlled trial.” British Medical Journal. 2009 Oct 29; 339:b4080. doi: 10.1136/bmj.b4080.