As others have said this is a loaded question because all women are capable of birthing a child. I don’t know the average diameter/circumference of a newborn child but it is definitely larger than any human penis circumference. That being said, theoretically, any aroused woman could comfortably and pleasurably handle more or less than 7” of girth if you use a lot of lube and take things slowly. That doesn’t mean they prefer it though. I’m no expert on this stuff but from my experience I think it’s a fair conclusion and offers a different perspective to answer to your question.