By Michelle Edgar, LM
One of the factors that sets the stage for a productive labor and normal vaginal birth is a baby in a good position at the end of pregnancy, especially at the time labor begins. At or around 32 weeks of pregnancy, most babies will have adopted a longitudinal lie (most head-down, some breech (bottom down) in the mother’s womb. Near the end of pregnancy as baby grows and has less room to move around, he tends to settle into a position with his back on either the mother’s right or left side. Ideally for most mama-baby pairs, a baby enters its mother’s pelvis head-down with its chin tucked toward its chest and its back on her left side. This is typically called optimal fetal positioning.
As midwives, we pay close attention to a baby’s position during prenatal visits. At every visit in the third trimester we use our hands to palpate the mother’s belly, feeling for the baby’s head, back, bottom and limbs.
If at 32 weeks we determine a baby is in a breech or other non-vertex (non-head down) position, we suggest a variety of techniques to our clients that they can practice on their own or with the help of other providers, such as a chiropractor or acupuncturist, to encourage the baby to turn while it is still small and has room to do so easily. Most babies will stay head-down once they switch, but some like to keep us on our toes until the very last minute! If by 36 weeks of pregnancy a baby has persistently remained in a non-vertex position despite efforts to help it turn, we counsel our clients about the risks and benefits of undergoing an external cephalic version. This is a procedure performed in hospital, under ultrasound guidance, with or without various medications for the mother, in which a doctor manually rotates the baby from the outside into a head-down position. Depending on a variety of factors, the overall success rate of this procedure is around 50%. It is usually performed at or after 37 weeks of pregnancy due to the chance of the baby reverting back to a non-vertex position while it may still have room, and also due to the small risk of the need for emergency Cesarean delivery if there is a problem during the procedure. If a baby continues to present non-vertex, her parents decide whether to try for a vaginal birth, or to consent to an elective Cesarean delivery, which is the standard of care at most area hospitals.
A more subtle determination is the position of the vertex baby’s head in the mother’s pelvis. Ideally the baby has its chin tucked toward its chest with its back easily felt along mom’s left side. Carrying a baby in this position at the end of pregnancy provides the greatest chance for a straightforward labor with either no or minimal medical intervention. If a baby persistently presents its back on the mother’s right side or towards her back, she is more likely to present occiput posterior, or “OP.” Mothers with babies presenting in OP have a greater likelihood of the pregnancy going late (possibly needing to induce labor), and of the mother experiencing the dreaded back labor.
Between 15-30% of babies are positioned OP at the time labor begins. This fetal position is associated with longer and more painful labors, increased need for medical intervention such as pitocin augmentation, vacuum or forceps-assisted delivery, 3rd and 4th degree perineal/anal lacerations and Cesarean section. There is also a correlation between the use of epidural anesthesia in labor and having a baby in a persistent OP position, and its attendant risks.
As midwives we are skilled in recognizing the dysfunctional labor patterns that often happen when a baby is presenting in a sub-optimal position, such as OP, asynclitic (baby’s head crooked) or de-flexed (baby’s chin not tucked toward chest). Throughout the course of prenatal care, we suggest ways our clients can encourage their babies to adopt an optimal position at the end of pregnancy. We use a variety of techniques including maternal postures and movements, manual rotation/flexion of the baby’s head, homeopathy, nutritional support and IV therapy to help avoid maternal exhaustion if indicated. We are also skilled in working with these mama-baby pairs to support them through a potentially longer, more painful labor and to help correct the baby’s malpresentation, thereby reducing the need for the medical interventions described above.
A baby in a suboptimal position at some point in labor is common and can happen to anyone. If you educate yourself, live a healthy, active lifestyle and build a skilled, supportive birth team, you will be in a good position to have a great birth.
–Michelle Edgar, LM, Nicole Sellers, LM and Ellah Ray, LM
East Bay Homebirth Midwifery
None of the information in this column is intended to be used for medical diagnosis or treatment. Talk with your healthcare provider about any questions you may have regarding a medical condition.