If a military force has actual pregnant women on the front lines in a wartime situation that tells me one thing - the country done fucked up, because that's all they have left. If you can't field an adequate male fighting force as the boots on the ground, you're completely boned from the get-go, because we've all seen the reports of how badly the women perform in Basic, even with lowered standards.

Besides which, as soon as an enlisted woman turns up pregnant, they pull her from active deployment and put her into a non-deployable unit. At that point they're effectively a drain on military resources until they're considered fit to return to active duty.