Is semi-fixed the same as already being engaged in the pelvis?

Generally, "semi-engagement" refers to the process in which the fetal head is descending into the pelvis but has not yet fully engaged. Semi-engagement indicates that the fetal head has started to descend but has not completely entered the pelvic cavity; it is a sign that engagement is imminent. The following is a detailed explanation:

During pregnancy, as gestational weeks increase, especially in the late stages, pregnant women often feel tightness in the abdomen or occasional abdominal pain. This is a normal phenomenon caused by the force pushing the fetal head downward, indicating that the fetal head is gradually descending. When the biparietal diameter of the fetal head reaches below the pelvic inlet of the mother and aligns appropriately with the pelvis, this condition is known as "fetal head engagement," suggesting that labor may be approaching. Therefore, fetal semi-engagement means the fetus is in the process of engaging into the pelvis. However, engagement does not necessarily mean immediate delivery. After engagement, pressure on the cervix may trigger uterine contractions; thus, before approaching the due date, pregnant women should moderate their physical activity appropriately.

Engagement refers to the process in late pregnancy when the fetus, surrounded by amniotic fluid and fetal membranes, assumes a position with head down and buttocks up, body curled, allowing the head to pass through the maternal pelvic inlet into the pelvic cavity, thereby stabilizing its position. Many pregnant women can perceive a downward shift in the fetus during engagement, sometimes accompanied by mild sensations of pressure or dull pain. The entire engagement process may take less than half a minute, but confirmation of whether engagement has occurred must be determined through obstetric examination.

If a pregnant woman experiences uterine contractions, abdominal pain, or other discomfort in late pregnancy, she should promptly go to the hospital to await delivery.