Well all three of the guys who are 7 inch girth or thereabouts who have commented here have said it’s not an issue. Small sample but I got to thinking about this baby head that keeps coming up. I looked around and did some research. Because that actually is testing the limits of what is possible.
The skeletal opening of the pelvis is about 15 inches girth. The pelvic musculature, rectum, and uterine walls limit the actual birth canal to about 12.5 inches girth, which is the girth of a baby’s head.
Most women’s vaginas cannot actually pass a baby’s head. 85% of women get a tear, and 65% of women require stitches.
In a study of vaginal and perineal tears during childbirth, the average tear is shown to be about 4 cm long, with the absolute longest tears being 8 cm long, but also rather rare. It looks like the 95% interval for tear length has a max at about 6 cm. So for a conservative estimate, let’s assume a 6 cm tear, which increases the girth of the vagina by 12 cm (6 cm for each side of the tear). So in theory, 95% of vaginal tears would not happen if the baby’s head size were 12 cm less (4.7 inches less).
That works out to a 7.8” girth - the size at which over 95% of women would not have any tears other than superficial skin stretching damage, and many would not even have that.
And that’s the conservative estimate. With the 4 cm average tear, plus the 15% of women who don’t even tear on the full 12.5” baby head, the “average scenario” would be that 65% of women would not tear on 9” girth.
Some more interesting thoughts. The vagina does not dilate with any birth hormones like the cervix, at least from my understanding and research (please correct me if I’m wrong). It just stretches out during stage two of childbirth as the baby passes through the birth canal over a period of 20 minutes to 2 hours. That’s it, it just stretches.
The 12 inch girth of a baby translates to about:
6 times as big as 5 inch girth
4 times as big as 6 inch girth
3 times as big as 7 inch girth
2 times as big as 8 inch girth
After looking into this deeper, I’m starting to think just about any woman could take 7 inches girth if she really wants it. Anatomically there’s nothing preventing it. She might need to learn how, and it might take 10 or 20 or 30 minutes and a lot of lube, but it should fit. It’s only one third the size of a baby. Maybe it would cause superficial skin damage for some, but in terms of actual tearing of the vagina or perineum, in terms of being physically unable to fit, it seems like nonsense to me now. Any healthy vagina should be able to fit 7 inch girth and probably 8 inch girth as well.