16 weeks pregnant with a sore waist and a slight pain in the stomach may be caused by physiological reasons, preeclampsia and other reasons. 1. Physiological reasons: 16 weeks of pregnancy, the bottom of the uterus has reached the umbilicus between the shame, the growing uterus will pull the surrounding ligaments and cause back pain and stomach pain, usually after appropriate rest can gradually ease, for the physiological phenomenon of pregnancy, do not need special treatment. 2. Pre-eclampsia: also cause back pain and stomach pain, accompanied by a small amount of vaginal bleeding, combined with clinical manifestations and ultrasound can help diagnosis, to comply with the doctor’s instructions to bed rest, and give progesterone and other medications to protect the fetus after treatment can be improved. When 16 weeks pregnant waist pain stomach pain need to go to the hospital, in order to identify the cause as soon as possible, and actively deal with.