I don't think you can lump everyone under "today's society" because I think the pressures vary by social group, religion, even geographic region of the country.
I don't think there's much premium in lying to one's children (especially if grown) because they can do the math. It's worse if they hear it from Aunt Susie after that second glass of wine, or if someone throws it out in anger.
I wouldn't hazard a guess - I think you can get statistics from more reliable sources that deal with pregnancy, sexuality and population studies.
I think abortion has always been available, and always will be, to women of means. For many years it was an option for all women, but now with so many (male) legislators placing extreme limits on women (waiting periods, forced vaginal probes and "counseling" for one purpose only), there's a disproportionate burden on poor and rural women who rely on clinics vs. private doctors. So I think the number of pregnancies is going up.
There is a growing acceptance of various family structures - single parents, married, two women, two men, adoptive, foster, grandparent, etc. - and there are protections for single women who now get child support. It didn't use to be that way. Technology helps - DNA testing and so on.
There are a few enclaves where it's not accepted, of course - someone posted a question about the Duggars the other day, for example. So I think that's a demographic group where the lie and the cover-up is more important because the truth is not accepted. (Child molestation okay, premarital sex not okay. But I digress….)
I have my great grandparents' marriage certificate - it's huge and is in an ornate frame, and includes their photos and dates. Any idiot could see that their oldest daughter was born 6 months later. I'm not sure it was discussed, but it wasn't hidden either. I was never told about it - I just did the math. I don't know how old my grandmother was when she found out.
I think a big factor in marriage due to pregnancy is the economics of it - we're just not very progressive in this country when it comes to paid and unpaid family leave (a mere fraction of what happens in most of Europe), benefits for single mothers (the poor get shamed all the time for needing welfare and WIC), day care (expensive, yet day care workers are underpaid), and of course women's salaries still lag way behind men's (it's up to 79 cents to the dollar, but that's still pathetic). The Equal Rights Amendment never passed in the 1970s, and Equal Pay is still critiqued and fought in the courts. So there's a very real economic pressure on women who may marry for protection or for the simple sharing of resources.
I do think the idea of pregnancy before marriage is addressed more matter-of-factly on TV shows though - so kids are exposed to it and it's far less of a big deal than it was 10 or 30 or 50 years ago. And in many states (far from all), kids are getting some sex education about real issues (not just abstinence only, which is where we see high teen pregnancy and STD rates), so other than the general discomfort that comes from teens thinking of their parents having sex, it's a more open topic.
For most older kids and certainly for adult kids, I think it's the "elephant in the room" - everyone knows about it but no one talks about it, because each person thinks the others will be uncomfortable.