The women showed marked differences in orgasm duration and the number of contractions.
[2] Vaginal contractions are caused by both the activity of certain brain regions and the release of the hormone oxytocin.
It has been suggested that vaginal contractions during orgasm can increase the chances of pregnancy as they transport sperm up the reproductive tract from the vagina to the oviducts, which decreases the distance it has to travel.
Additionally, when the woman is fertile, sperm is only transported to the side of the dominant ovary.
Involuntary spasm of the muscles around the vagina, usually caused by anxiety, can result in vaginismus.