There's a huge difference between engaging in normal adventuring activity and engaging in sex. People agree to go into dungeons and battle ogres. Agreeing to have sex is not the same thing as agreeing to get pregnant.
You are being unnecessarily punitive to women who decide to have sex.
You're the first person who's raised any issue with this. No-one at my tables ever has, including the many women who have played here.
Thinking about it, over the years there's been four instances of PC pregnancy in my games that resulted in a child born while the campaign was still underway.
The first was a PC monarch, intentionally trying to produce an heir. Her consort (later, husband) was another PC. They married, she got pregnant (and retired from adventuring), had the baby, then was on-and-off back in the field until the campaign ended. The father kept adventuring pretty much throughout, in part because both mother and child needed defending from threats specifically against them.
The second was an accidental pregnancy through a fling with an NPC; the PC decided to keep it (yes, abortion is always an option), had the baby, gave him off to a nanny, and returned to the field. Meanwhile, as fate would have it the rest of the party took much of that time off, so she didn't miss much adventuring while pregnant.
The third was two PCs whose relationship started (in mid-adventure!) as a no-holds-barred passionate fling and then just kept going; on learning she was pregnant (which was received as good news) they decided to settle down, get married, and retire from adventuring.
The fourth was again two PCs, this one was an accidental pregnancy that the PC decided to keep. This was the one noted upthread, where she adventured until late-term then took to the field again almost immediately after the birth (there's a lot more to that which would take far more explaining than it's worth). Later, threats against the baby (another very long story) led to her and the child hiding on a different world and retiring completely; the father still adventures but visits when he can, using his treasure to pay for their (rather luxurious!) upkeep.
If it matters, in all four cases the players of the mother PCs were women, as was the player of the father in the third instance above.