women s health issues
Fetal Presentation, Position, and Lie (Including Breech Presentation)
Introduction
During pregnancy, the fetus can be positioned in many different ways inside the mother's uterus. The fetus may be head up or down or facing the mother's back or front. At first, the fetus can move around easily or shift position as the mother moves. Toward the end of the pregnancy the fetus is larger, has less room to move, and stays in one position. How the fetus is positioned has an important effect on delivery and, for certain positions, a Cesarean Delivery is necessary. There are medical terms that describe precisely how the fetus is positioned, and identifying the fetal position helps doctors to anticipate potential difficulties during labor and delivery. Presentationrefers to the part of the fetus’s body that leads the way out through the birth canal (called the presenting part). Usually, the head leads the way, but sometimes the buttocks (breech presentation), shoulder, or face leads the way. Positionrefers to whether the fetus is facing backward (occiput anterior) or forward (occiput posterior). The occiput is a bone at the back of the baby's head. Therefore, facing backward is called occiput anterior (facing the mother’s back and facing down when the mother lies on her back). Facing forward is called occiput posterior (facing toward the mother's pubic bone and facing up when the mother lies on her back). Lierefers to the angle of the fetus in relation to the mother and the uterus. Up-and-down (with the baby's spine parallel to mother's spine, called longitudinal) is normal, but sometimes the lie is sideways (transverse) or at an angle (oblique). For these aspects of fetal positioning, the combination that is the most common, safest, and easiest for the mother to deliver is the following: Head first (called vertex or cephalic presentation) Facing backward (occiput anterior position) Spine parallel to mother's spine (longitudinal lie) Neck bent forward with chin tucked Arms folded across the chest If the fetus is in a different position, lie, or presentation, labor may be more difficult, and a normal vaginal delivery may not be possible. Variations in fetal presentation, position, or lie may occur when The fetus is too large for the mother's pelvis (fetopelvic disproportion). The uterus is abnormally shaped or contains growths such as Uterine Fibroids . The fetus has a Overview of Birth Defects . There is more than one fetus (multiple gestation). Toward the end of pregnancy, the fetus moves into position for delivery. Normally, the presentation is vertex (head first), and the position is occiput anterior (facing toward the pregnant person's spine) and with the face and body angled to one side and the neck flexed. Variations in fetal presentations include face, brow, breech, and shoulder. Occiput posterior position (facing forward, toward the mother's pubic bone) is less common than occiput anterior position (facing backward, toward the mother's spine). 