The pain below the navel in the fifth month of pregnancy may be caused by physiological factors, or it may be the case of preterm labor. 1. physiological factors: in the course of pregnancy, due to the gradual growth of the fetus, the uterus is compressed, may lead to uterine ligament pulling, so the symptoms of hidden pain below the navel, this situation is generally normal, basically will not have an impact on the body. 2. Preterm labor: In the fifth month of pregnancy, if the uterus contracts frequently, the phenomenon of preterm labor, may produce the symptoms of hidden pain below the navel. 5 months pregnant need to pay more attention to rest, regular medical care for all pregnancy checkups, usually also need to maintain a good state of mind.