sperm helps soften and ripe the cervix.. orgasming make you contract which can lead into labor .. 😊

The only way sex is effective to start labor is nipple stimulation (which you could do yourself) or if he ejaculates if he doesn't it's not nearly as big of a chance because the sperm acts as a softening "agent" for your cervix.

I think it's more sperm than anything else sex related that helps start labor. The contractions from an orgasm might help, but idk.

I've heard they do, not sure though haha

sex can start labor