...and I thought the fact that she got the birth control pills at the beginning of the series could only add to that willful denial.

I didn't even think of that, but it's consistent. So she's been taking these pills and either they didn't work or she didn't take them right, but she still believes that she can't possibly be pregnant - all obvious signs of pregnancy notwithstanding. People were certainly less informed about birth control back then.

she still believes that she can't possibly be pregnant - all obvious signs of pregnancy notwithstanding.

I think that this is it. Girls back then didn't realize the importance of things like taking it at the same time every day.

...and I thought the fact that she got the birth control pills at the beginning of the series could only add to that willful denial.

This was certainly how I saw it - and it* was set up from the first episode. I mean, now, you get this whole "start taking these on THIS day, and no later than THAT day, and back up with a barrier method for the rest of the cycle, and if you miss a pill, do this but if you miss two pills..." and on and on. With Peggy, it was "here's your magical script, don't be a whore."

* And I don't even think that the "it" here needs to be total ignorance that anything at all was going on -- just a route for her to deny, deny, deny.

And as the pregnancy advanced, she had more and more emotionally invested in sustaining that denial.

She was getting positive attention, praise, special assignments and scraps of privilege from the execs, and very badly didn't want to do anything that might jeopardize that (damn, "jeopardize" is a hard word to spell!). Her quasi-privileged position with the higher-ups completely isolated her from any of the women who might have been friends and confidantes, and, of course, despite her quasi-privilege, her femaleness nearly totally isolated her from the clubby world of the higher-ups.

And we got small hints that her mom wasn't thrilled to have her out there in the big city and wanted her safely home and married and domestic, adding yet another layer of "Everything in my universe depends on not admitting any weaknesses or screw-ups."

I don't find her very likable, but I still feel horrible for how utterly alone she is and how much she's having to fight her way through with no friends, no mentors, nobody really on her side but herself (and maybe, slightly, Don, but he seems more dog-dancing-on-its-hind-legs amused at her smarts than anything more seriously positive). And when that last plot twist hit, I found myself both personally repelled by it and nodding and saying, "Yeah, I can't believe it makes sense, but it completely does."

JZ has my proxy. I bought it entirely for those reasons. In fact, that was exactly what I thought was happening once they started putting her in the fat suit.

She was getting positive attention, praise, special assignments and scraps of privilege from the execs, and very badly didn't want to do anything that might jeopardize that (damn, "jeopardize" is a hard word to spell!). Her quasi-privileged position with the higher-ups completely isolated her from any of the women who might have been friends and confidantes, and, of course, despite her quasi-privilege, her femaleness nearly totally isolated her from the clubby world of the higher-ups.

Yes, so very much this! If it came out that she was pregnant, her career would be over.

Also, who is going to go back to a doctor who says "don't be a slut" about any concerns you might have about taking the pill?

So she's been taking these pills and either they didn't work or she didn't take them right,

Didn't she get the pills *after* her night with wassisname "Connor"?

Didn't she get the pills *after* her night with wassisname "Connor"?

I thought it was before, but you need to be on the pill for a full cycle for them to be totally effective.

Didn't she get the pills *after* her night with wassisname "Connor"?

Right before -- like, the day of. Certainly not long enough to be effective.

with wassisname "Connor"?

Pete.

I'd have laughed my ass off if his character's name had been some form of William.