The fertilized egg may be laid in the fallopian tube or in the uterine cavity of the uterus, but no matter where it is laid, it usually does not cause tightness in the belly. Most women experience a drop in body temperature when the fertilized egg is implanted, and some women also experience back pain and backache. Tightness in the belly is usually caused by cold, diarrhea in the abdomen or anger, and if the usual diet is irregular or the spleen and stomach are damaged causing indigestion, tightness in the belly may also occur as the condition develops. Women with gynecological diseases, such as inflammation of the pelvis or peritoneum, will also experience tightness in the belly, which is caused by inflammatory stimulation of the patient and abdominal pain.