I was talking more about anal sex than anything else actually. Although girl on top anal sex would be impossible and guy's penis can have irreversible damage due to constriction of the anus but if the girl is on all four, that might be achievable since lot of girls prefer to give birth that way. Nonetheless, I think sexual stimulation is probably the greatest natural birth one can have.
I agree about the infection part since this process can surely take in different turn, if they are not careful since the umbilical cord is the most vulnerable part after birth and if it isn't cut antiseptically, the kid can end up getting lot of deadly diseases, such as tetanus, and hepatitis. The mother could be in danger, too but what I have seen, in terms of home birth, not lot of couples take that precaution when they consider of natural birth so I am not sure what infection they are worrying about. If the guy does not have any diseases, he doesn't have to worry too much. And cumming inside to stimulate the cervix is just as normal as cumming inside before the pregnancy. I don't thinking ejaculating inside while in labor does anything anyway haha.
By the way, I have heard similar stories, too and some are claimed to be true. I also heard that during childbirth, if both couples are completely naked, and if the guy has erection during the process, the girl seems more attached. Again the childbirth process is something biological and sexual so not sure why it is taboo and lot of society are against sex during childbirth. I heard that in some countries couple never even have sex during pregnancy and just stay very protective because their idea is that if the penis is entered, it may damage the developing embryo, yes even during 8th or 9th of pregnancy when the embryo is fully developed.
I think the major concern lot of people have is the safety of the baby but if that is taken as a precautionary measure, this task can be achieved. Damn if only my gf was interested to get pregnant, I could have convinced her to try that out haha. Oh well...
Oh and I heard about that porn star being pregnant and wanted to give birth on the movies. I thought she was a Swedish porn actress or something. I think the society probably has this checked correctly because there are lot of sickfucks out there that can manipulate this, like drugs and prostitution, so I can see why it maybe a good thing that is forbidden...Ah well fantasy is a fantasy, I guess, and possibly should stay that way.