When you are trying to conceive, anything that might help without being invasive is usually worth a try. There is even scientific proof, though limited, that show some of the folklore regarding sexual positions aiding conception may have merit.
Best sexual positions for conception
It is possible to conceive from any sexual position, but those which allow deepest penetration may have an advantage over others because they allow the sperm to get closer to the opening of the uterus. The two positions that offer the deepest penetration are the man on top and entry from behind. To further aid penetration, a woman can place a pillow under her hips during intercourse in the man on top, or missionary, position. Regardless of position, some research indicates that the woman should remain on her back for half an hour after intercourse to give sperm the opportunity to make their way into the uterus.
Worst sexual positions for conception
Again, it is possible to conceive by using any sexual position. Yet, as there are positions that are more likely to result in conception there are also positions that are thought to be less conducive to conception. Any position that makes it more difficult for the sperm to reach the uterus due to gravity is considered to be undesirable for conception. These positions include intercourse while standing or while the woman is sitting.
Female orgasm and conception
Men must have an orgasm in order to procreate, but what about women? While it is not necessary for a woman to have an orgasm to conceive, it turns out that it might be helpful. Research is beginning to indicate that when a woman has an orgasm the contractions of the uterus may be beneficial in helping the sperm move into the womb. This works best when the woman has an orgasm at the same time as or soon after her partner. However, unlike male orgasm, it is not essential to conception.
Should you lie down for some time after he ejaculates?
There is a common perception that you can improve your chances of getting pregnant by staying on your back for 15 minutes after he ejaculates. Should you or shouldn't you stay on your back? The scientific literature looked into whether a woman lying on her back can improve her pregnancy chances after IUI, intrauterine insemination is divided on this question. One study from 2017 concluded that "..this study shows no positive effect of 15 min of immobilization following IUI on pregnancy rates...". However, another study concluded that lying down after insemination improved pregnancy and it showed a "...persistent significant difference in ongoing pregnancy rates and underpins the importance of immobilization after IUI...".
Neither study concluded that there may be harm from lying down for 15 minutes after insemination. In medical science, when there are different findings, we usually try to find out whether one option could be more harmful than the other. Given that there is evidence that lying down may help and there is unlikely any harm in lying down after sex for 15 min, there is no valid reason to tell women to not lie down for 15 min after sex. If in doubt, decide yourself.
If you want a boy
It is possible to have a boy regardless of what sexual position you choose. However, there is a great deal of advice that may increase your chances of having a boy. Deep penetration is ideal if you want to have a boy because it makes it easier for the male sperm to reach the egg. Additionally, it is thought to be helpful if your mate keeps his testicles cool and unrestricted by tight underwear and pants. Finally, to increase your odds of having a boy, legends say that you should make love at night on odd days and especially on the day of ovulation.
If you want a girl
Just as with a boy, it is possible to have a girl no matter what sexual positions you choose. Again, though, there are positions that are favored by those who wish to have a girl. Choose those positions that allow for shallow penetration. Finally, make love in the afternoon on the even days and especially in the few days prior to ovulation.