Don't embarrass either one of you by assuming a weight gain is a "baby bump." Give her some time to broach the subject
One of the young women in my department is either gaining weight in her lower abdomen or she's displaying what the celebrity magazines call a "baby bump." I don't know how to address the issue with her. Maybe the best course of action is to stay silent until she says something to me, but the more time I have to plan for an upcoming maternity leave, the better for me as the manager. How long should I wait before broaching the topic? If I do say something, what is the polite way to inquire about her parental status?
Many a hapless manager and colleague has been tripped up by a belly-centric weight gain masquerading as early pregnancy. To avoid embarrassment for yourself and your employee, say nothing for as long as possible. If your employee is indeed expecting a baby, it's her privilege to keep the news to herself until she's in a later stage of her pregnancy. Early on, the risk of miscarriage is the highest, and for this reason many expecting moms keep mum until they're well into their second trimester.
If your employee is pregnant, you won't be guessing about it a few months from now, because she'll be "showing" in a much more obvious way than she is now. In the highly unlikely event that her tummy keeps growing and she hasn't addressed the maternity-leave issue with you, you can consult with your HR representative about the best way to handle the issue. That might be as simple as estimating as best you can the rough timeframe for your employee's due date and asking her, "Pam, will you be available for a [trip to China, stint in a trade show booth] around Mar. 17?"