Can nipple stimulation bring on labor?
Nipple stimulation can be used to make the uterus cramp. This is useful after the baby is born to help the placenta separate from the uterus, or after the placenta is delivered to help the uterus contract and decrease postpartum bleeding. The same effect will happen if you place the baby on the breast to breastfeed -- the sucking will make the uterus cramp. Mom will feel these cramps when she breastfeeds.
But nipple stimulation (by rolling or rubbing the nipples) is not advised because it can cause cramps or contractions, or even bring on labor (premature or term). These cramps are usually mild, but strong and frequent contractions could stress your baby.
Other causes of uterine cramping in the third trimester include orgasm, breast and nipple stimulation by your partner, dehydration, urinary tract infections, and labor. When you shower, it's better to direct the water toward your back rather than toward your breasts.
You should notify your midwife or doctor if you have regular uterine contractions (four to six cramps or contractions in an hour) if you are less than 36 weeks pregnant. Drink lots of water and urinate frequently.