Regarding the orgasm thing, it wasn't some experts - it was a fundamental tenet of reproductive medicine until the 18th century. Every fertility manual in the early modern period states outright that women have to enjoy sex in order to conceive, and some give a pretty detailed description that certainly suggests orgasm.

As for sexual performance and fertility, certainly in order to get a woman pregnant, a man had to be able to perform, and impotence was actually grounds for annulment (unlike infertility). A whole branch of reproductive medicine was based on providing aphrodisiacs to members of both sexes in order to ensure everything worked well, for which I have to refer you to the work of my colleague, Jennifer Evans: http://www.boydellandbrewer.com/store/viewItem.as...

Actually, the completely anecdotal and lacking-scientific-rigor evidence of my study suggests that Catholic women had fertility problems about as much as Protestant ones (especially if they happened to be a queens or from aristocratic families. Granted, these factors may have been more significant).

The ones who really seem to be having large families are Quaker women. Again, totally anecdotal and unscientific, but I've looked at quite a few Quaker documents from this period, because these were women who left more historical records than most, and all of them seemed to average at 9-10 children per woman. I've yet to find a childless one.

Exactly this.

Legality mattered a great deal in the early modern period (in which, by the way, nuclear families were the norm and couples waited until they could afford to start their own household before they got married).

It defined inheritance law, which was crucial if you had anything to leave your children - and this actually became *more* important during this period. In the middle ages you could (broadly speaking) write a will naming anyone you wanted as your heir. Over time, stricter rules developed until you were basically required to leave your estate to specific legal heirs even if you preferred something different. Hence the whole Jane Austen drama about not being able to leave the estate to the girls and needing them to marry well.

While I'm not an expert on this, I would hazard a guess that the lack of formal adoption laws was not the result of a more open and fluid view of family, but rather of a very real concern over allowing people to circumvent rules about inheritance by adopting. The concept of legal adoption existed because it had been in existence in Classical Rome, and some European countries at least contemplating allowing it in this period, but this was contentious precisely because it placed ideas about blood ties and formal inheritance into question.

Thanks for this comment! The history of adoption has been proving more difficult to research than I expected, and of course this is why.

This is actually a bit complicated. The medical texts all recognize that male infertility is possible, but the real-life cases all "blame" the woman. So the idea that it could be the man was there, but basically wasn't acted upon.

I could write a whole post (or, well, a whole book) about this, but the short answer is that it's part of the same or a similar doctrine.
The kind of "improper" behavior that causes infertility in the medical texts is sinful behavior (lust, excess eating, idleness, anger etc.) - so implicitly or explicitly the medicine is reinforcing the religious view.
You do get a different emphasis on religion depending on whether the person is from the "godly" crowd or not, but it's there in the background regardless.

Quickening had a special status, certainly, and it was something that people looked for in pregnancy and was seen as a positive sign.
However, it was understood that this wasn't certain. Women could mistake other things for quickening, (I've seen "wind in the stomach" as the most frequent culprit). Cathy McClive has done great academic work on this, here for example: http://shm.oxfordjournals.org/content/15/2/209.ab...

So I've actually just been looking more into this recently. It appears that in Early Modern England there is actually *no* legal adoption, in the sense of making someone formally your child and heir. There was legal adoption in a few other European countries in this period, but still quite rare and contentious. In England, however, you couldn't do it.
So when I write about "informal adoption", I mean taking on the education and care of (usually) children/young adults who are not directly related to you, and acting in a role that is like that of a parent, but without making them your legal heirs.