The tightness and hardness of the small abdomen at 16 weeks of gestation is caused by occasional contractions of the uterus, which will soon be relieved on their own. Don’t be overly nervous, usually don’t often use your hands to stimulate your abdomen, try to avoid lying down, rest on your side, and move appropriately, which occasionally appears to be relieved on its own and will not affect the growth and development of the fetus. It does not need special treatment and regular maternal checkups are possible. It may also be a fetal movement process, feel the fetal movement earlier in 16 weeks, the average in about 18 weeks, the gestational week increases fetal movement gradually obvious, this pregnancy week need to do maternity checkups, mid-term screening of Down screening, and book fetal system ultrasound teratology examination, if you feel the abdomen tight, hard frequent, rest can not be relieved, or persistently not relieved, you need to consult at any time, to see the intrauterine development of the fetus and length of the cervical canal for signs of preterm abortion.