During pregnancy, and especially through the homestretch, you store up quite a bit of fluid. Are your feet so swollen that your shoes don't fit anymore? And what about your wedding rings? Postpartum perspiration is one way to get rid of this excess fluid. In addition, you can blame hormones for the reason you're waking up drenched in sweat. "There's also some hormonal changes," notes Dr. Cline. She explains, "Your estrogen levels are lower, particularly immediately postpartum, which can cause you to sweat and have hot flashes." What a great warm-up for menopause!