16 weeks belly button contractions are usually not contractions.
Contractions are a relatively common phenomenon during pregnancy, mainly with the progression of pregnancy, the intrauterine volume increases, the growth rate of the uterine wall increases, the uterine wall contraction sensitivity increases so as to appear, but most often seen in the middle of pregnancy and the end of pregnancy. As the amniotic fluid gradually decreases and the fetus continues to grow, both the fetus and the uterine wall can be stimulated to induce uterine contractions, but they are usually seen at the end of pregnancy.
And 16 weeks pregnant belongs to the early stage of pregnancy, generally will not appear this phenomenon, consider because the abdomen is cold or intestinal inflammation, etc., resulting in muscle spasm contraction of the navel area, and cause abdominal pain symptoms of more reasons, generally will not be the contraction of the uterus.
16 weeks navel contraction, if accompanied by other symptoms of discomfort, should promptly consult a doctor to find out why.