In a perfect world, you'd get to enjoy your curvaceous pregnancy breasts without pain or problems. But for most women, a bigger chest brings a little tenderness and sometimes an annoying phenomenon known as nipple discharge, or leaking.
Leaking breasts during pregnancy is pretty normal, and it's caused by an imbalance in pregnancy hormones. "During pregnancy, your body releases prolactin, a key hormone that promotes milk production," says Patrick Duff, M.D., an Ob-Gyn at the University of Florida, Gainesville. With prolactin levels surging, your pregnancy breasts are raring to go – filling up with colostrum, the early form of breast milk, so you'll be ready to feed your new little one.
At the same time, estrogen made by the placenta is acting to prevent the secretion of milk, in order to suppress it until the baby arrives. "Sometimes the balance of prolactin and estrogen isn't perfect. It's like having your foot on the gas and the brakes at the some time, sometimes the accelerator overrides the stopping mechanism," says Duff. "And a little bit of milk can leak out."
"The estrogen in your system usually keeps your milk production in check," adds Sharon Phelan, M.D., a professor of obstetrics and gynecology at the University of New Mexico Health Science Center School of Medicine. "However, if your nipples are stimulated, it can trigger the milk to be expressed." This can happen in a number of ways. Breasts stimulated during foreplay might discharge a few drops, and activities where the nipples rub against your clothing (say, a brisk walk or Zumba class) could also cause the breast to leak clear fluid.
Many doctors claim that breasts start developing colostrum at around 14 weeks, but some women start leaking before then. "Some women may go their entire pregnancy without leaking, but seeing a few drops of liquid is normal," says Phelan. If you experience more leaking than that, or if you're noticing a thick discharge or spots of blood, it's a good idea to make an appointment with your Ob-Gyn. "Those are signs of mammary duct ectasia, or a clogged milk duct, which is easily treated by your doctor," says Duff.