The Significance of Fetus Position

During labor, the baby moves through the birth canal and emerges through the vaginal opening. Toward the end of the pregnancy, the health care provider will perform physical examinations to determine the baby’s position in the uterus. This position, which medical professionals call the fetal lie, can forewarn the practitioner of any potential risks or difficulties during delivery. Some positions can prevent the baby from passing through the pelvis.

The most common birth position is a cephalic presentation, meaning that the head is facing downwards. The weight of the fetus’ head puts pressure on the cervix and helps widen it, making delivery easier. An occiput anterior position is when the baby is head-down and faces the mother’s back. The neck is bent forward, the chin is tucked in, the body angles to one side, and the arms fold across the chest. Physicians say this is the best and safest position for passage through the birth canal. Babies usually go into this position between 32 and 36 weeks, though some do not transition until days before the delivery date.

Sometimes the fetus is headfirst but facing the mother’s abdomen instead of her back. Doctors call this face-up, abnormal presentation the occiput posterior position. The problem with this position is that the baby’s neck is straight instead of bent, so he or she requires more space to pass through the birth canal. In most cases, the fetus turns to face the mother’s back before the delivery. If the baby does not turn, complications can arise and the obstetrician may use forceps, a vacuum extractor, or perform a cesarean section to ensure a safer birth.

Face presentation occurs when the face and chin are facing downward. If the baby is in a brow presentation, the chin is untucked, and the face presents first, but the neck is less extended than that of the face presentation. A natural delivery is usually not possible when the fetus is in one of these positions because, again, the head requires more room to pass through the pelvis. Sometimes, a safe vaginal delivery is possible in these cases, if the mother has a larger pelvic opening or the fetus is quite small. Doctors discover these presentations through a physical examination during labor or with an ultrasound.

About 4% of babies present feet or buttocks first. In many cases, before labor begins, the doctor can turn the fetus so that the head presents first. If the physician cannot reposition the baby, the mother may require a C-section.

• If the baby is in a complete breech fetus position, the buttocks lead the way into the birth canal, and the legs are folded.
• A frank breech also indicates the buttocks lead the way, but the knees are in front of the body, and the feet are close to the head.
• In a footling breech position, the feet will deliver before the rest of the body. One or both of the baby’s feet point downward.

Sometimes a baby lies horizontally across the uterus. One shoulder is closest to the pelvis, meaning it will enter the birth canal first. In other cases, the baby’s back faces the birth canal. Occasionally, the back faces upwards, with the feet and hands near the birth canal. This is the transverse lie position; generally, the obstetrician can physically rotate the baby into the correct position before labor. However, if labor has started, the doctor will likely perform a C-section instead.

When there are twins, one baby is usually headfirst, and the other is breech. If the lower twin is positioned headfirst, the physician can usually deliver her normally through the vagina then attempt to rotate the second baby into a cephalic or head-first position or a buttocks-first breech position. This often results in a normal delivery. However, if the lower twin is breech, the physician will perform a C-section to deliver both babies safely.

In most cases, the growing fetus moves into the optimal position for birth before delivery. However, some babies face issues that prevent this from occurring. In the case of preterm labor -- labor that starts too soon -- the baby may not yet have moved into the proper position. A mother with fibroid tumors or whose uterus has an irregular shape is more likely to experience positioning issues. Congenital disabilities, long and difficult labors, or very rapid ones also lead to abnormal positions that increase birthing difficulty. Women with diabetes and those with obesity are also more likely to face birth position issues.

In some cases, physicians try to turn the baby and place it in the best position for the delivery. This procedure has a high success rate. Some doctors first prescribe a medication to relax the uterus. Ultrasounds not only help the physician determine the baby’s position, but they also provide the location of the placenta and the amount of amniotic fluid in the mother’s uterus. The physician gently applies pressure to the abdomen and then physically manipulates the baby into the best delivery position.

Many of us find comfort in tucking our knees up into our chests and curling into the "fetal position." Research suggests that when adults curl up into the fetal position, they are experiencing anxiety or sensitivity to a situation. A majority of people sleep on their side in a fetal position. Studies say that women are twice as likely as men to prefer this sleeping method. Other studies found that the fetal position creates a feeling of comfort and security. Furthermore, it can reduce snoring and relieve back pressure in some individuals.