Women need to be on their period first before they get pregnant. Let's be generous and assume half of them didn't had it during their turn. That already eliminates 1 million possible pregnancies.

Now let's assume half of them refused even if it means death like OP picture. That eliminates another 500k possible pregnancies.

Now let's assume the remaining 500k had an abortion. 1927 court decision allowed women to have an abortion in case of grave danger to the mother. That is if we can even assume something like upholding law in a country that has been ravaged by war. That's 250k aborted, legally/safely or not.

Now let's assume that out of 250k babies that were born survived into adulthood. It's reasonable to assume that they did not because rapey soldiers wouldn't bother to stick around to provide for their rape child. That's 125k babies that died from malnutrition or abandonment, if not more.

Now let's assume that out of 125k that somehow managed to make it through it all and decided to remain in a devastated country. Sensible to assume that they would not because their homeland was a wreck and they had no healthy family ties that would bind them. Let's cut it down by another half and that remains another 62.5k.

37k registered bastards sounds reasonable.