I have tried with a household with 1 male scientist and 2 young adults all being abducted at the same time. None of them got pregnant after 8 reloads. (didn't go for 20 this time, with the three of them, 8 reloads should be enough).
This is what I discovered about male scientist abductions and pregnancy:
The first signs of pregnancy occur exactly 2 hours after they return. They get a tummy ache. After exactly 24 hours after returning they know they're pregnant. They give birth exactly 5 days after the abduction and at exactly the same time they were abducted.
It was also easy getting a scientist pregnant: get him to the highest level as a scientist, call aliens and let him do something outside at 10 pm (super focused). If lucky they'd always be abducted at 10:10 pm, it also works when I let the Sim travel somewhere and come back before midnight.
As you can see I'm an expert at male scientists abductions and pregnancy LOL.
The only thing that has changed is that my 3 males were genetically engineered (new feature in "household"). My male Sim chose to have a genetically engineered baby as a single parent.
Now I will try and find an older file or a Sim created before the last patch and test again. If that works, the problem is linked with the new patch.
When did you find out your Sim was pregnant? Did you know after 2 hours or did you have to wait longer than that.