I think all-in-all....if rewards collerates with results achieved --then it is a good thing irregardless of being single, with kids, without kids or married.
I don't care if people are pregnant or have kids. Honestly, women(or men) who take off for a long time from work do pay the price for it. For example, most women here are entitled to 6 months paid maternity leave and 6 months non-paid. Those who are ambitious don't take that 6 months and have their husbands contirbute too. Those who are not ambitious will take the full 12 months followed by many unofficial "MIA" time or sick days.
If I have to cover for my pregnant colleague and I get more rewards/recognition than her, then I can see this as an opportunity for me to move up. So it's win-win. She gets her baby and maternity leave and I get a promotion. Rewards = Results
:O)