Yes, it can if done too much and can result in abdominal pains and cramping. However, strengthening your stomach muscles for a few seconds is advisable. This is because it helps with back pains and moves the baby to a perfect position for birth though you should consult your doctor.
i have heard to take it easy and relax. protect the tummy. you really should ask a doctor....I think a lot of intense movement during any stage of pregnancy, any forceful repeated movement, could at worse cause a miscarriage. find out from doc if tightening stomach muscles is ok.