A pregnancy that has progressed without any apparent hitch can still give way to complications during delivery. Here are some of the most common concerns.
Failure to Progress (Prolonged Labor)
A small percentage of women, mostly first-time mothers, may experience a labor that lasts too long. In this situation, both the mother and the baby are at risk for several complications including infections.
Presentation refers to the position the fetus takes as your body prepares for delivery, and it could be either vertex (head down) or breech (buttocks down). In the weeks before your due date, the fetus usually drops lower in the uterus. Ideally for labor, the baby is positioned head-down, facing the mother's back, with its chin tucked to its chest and the back of the head ready to enter the pelvis. That way, the smallest possible part of the baby's head leads the way through the cervix and into the birth canal.
Because the head is the largest and least flexible part of the baby, it's best for it to lead the way into the birth canal. That way there's little risk the body will make it through but the baby's head will get hung up. In cephalopelvic disproportion, the baby's head is often too large to fit through the mother's pelvis, either because of their relative sizes or because of poor positioning of the fetus.
Sometimes the baby is not facing the mother's back, but instead is turned toward her abdomen (occiput or cephalic posterior). This increases the chance of painful "back labor," a lengthy childbirth or tearing of the birth canal. In malpresentation of the head, the baby's head is positioned wrong, with the forehead, top of the head or face entering the birth canal, instead of the back of its head.
Some fetuses present with their buttocks or feet pointed down toward the birth canal (a frank, complete or incomplete/footling breech presentation). Breech presentations are normally seen far before the due date, but most babies will turn to the normal vertex (head-down) presentation as they get closer to the due date. In a frank breech, the baby's buttocks lead the way into the pelvis; the hips are flexed, the knee extended. In a complete breech, both knees and hips are flexed and the buttocks or feet may enter the birth canal first. In a footling or incomplete breech, one or both feet lead the way. A few babies lie horizontally (called transverse lie) in the uterus, which usually means the shoulder will lead the way into the birth canal rather than the head.
Abnormal presentations increase a woman's risk for injuries to the uterus or birth canal, and for abnormal labor. Breech babies are at risk of injury and a prolapsed umbilical cord. Transverse lie is the most serious abnormal presentation, and it can lead to injury of the uterus (ruptured uterus) as well as fetal injury.
Your doctor will determine the presentation and position of the fetus with a physical examination. Sometimes a sonogram helps in determining the fetus' position. When a baby is in the breech position before the last six weeks to eight weeks of pregnancy, the odds are still good that the baby will flip. However, the bigger the baby gets and the closer you get to the due date, the less room there is to maneuver. Doctors estimate that about 90% of fetuses who are in a breech presentation before 28 weeks will have turned by 37 weeks, and over 90% of babies who are breech after 37 weeks will most likely stay that way.
Umbilical Cord Prolapse
The umbilical cord is your baby's lifeline. Oxygen and other nutrients are passed from your system to your baby, through the placenta and the umbilical cord. Sometimes before or during labor, the umbilical cord can slip through the cervix, preceding the baby into the birth canal. It may even protrude from the vagina. This is dangerous because the umbilical cord can get blocked and stop blood flow through the cord. You will probably feel the cord in the birth canal and may see it if it protrudes from your vagina. This is an emergency situation. Call an ambulance to get you to the hospital.
Umbilical Cord Compression
Because the fetus moves a lot inside the uterus, the umbilical cord can get wrapped and unwrapped around the baby many times throughout the pregnancy. While there are "cord accidents" in which the cord gets twisted around and harms the baby, this is extremely rare and usually can't be prevented.
Sometimes the umbilical cord gets stretched and compressed during labor, leading to a brief decrease in the flow of blood within it. This can cause sudden, short drops in the fetal heart rate, called variable decelerations, which are usually picked up by monitors during labor. Cord compression happens in about one in 10 deliveries. In most cases, these changes are of no major concern and most babies quickly pass through this stage and the birth proceeds normally. But a cesarean section may be necessary if the heart rate worsens or the fetus shows other signs of distress, such as decrease of fetal blood pH or passing of the baby's first stool (meconium).
Causes and Treatments Failure to Progress (Prolonged Labor)
Failure to progress refers to labor that does not move as fast as it should. This could happen with a big baby, a baby that does not present normally or with a uterus that does not contract appropriately. But more often than not, no specific cause for "failure to progress" is found. If labor goes on too long, your doctor may give you intravenous fluids to help prevent you from getting dehydrated. If the uterus does not contract enough, he or she may give you oxytocin, a medicine that promotes stronger contractions. And if the cervix stops dilating despite strong contractions of the uterus, a cesarean section may be indicated.
Sometimes a placenta previa may cause an abnormal presentation. But many times the cause is not known. Towards the end of your third trimester, your doctor will check the presentation and position of your fetus by feeling your abdomen. If the fetus remains in breech presentation several weeks before the due date, your doctor may attempt to turn the baby into the correct position.
One option typically offered to women after 36 weeks is an "external cephalic version," which involves manually rotating the baby in cog-like fashion inside the uterus. These manipulations work about 50% to 60% of the time. They're usually more successful on women who have given birth previously because their uteruses stretch more easily.
"Versions" typically take place in the hospital, just in case an emergency cesarean delivery becomes necessary. To make the procedure easier to perform, safer for the baby and more tolerable for the mother-to-be, doctors sometimes administer a uterine muscle relaxant, then use an ultrasound machine and electronic fetal monitor as guides. The procedure typically doesn't involve anesthesia, but sometimes an epidural can help with the version. Since not all doctors have been trained to do versions, you may be referred to another obstetrician in your area.
There is a very small risk that the maneuver could cause the baby's cord to become entangled or the placenta to separate from the uterus. There's also a chance that the baby might flip back into a breech position before delivery, so some doctors induce labor immediately. The risk of reverting to breech is lower closer to term, but the bigger the baby, the harder it is to turn.
The procedure can be uncomfortable, but avoids a cesarean section, which is most likely if the baby can't be moved into the proper position.
Umbilical cord prolapse happens more often when a fetus is small, preterm, in breech (frank, complete or incomplete/footling) presentation, or if its head hasn't entered the mother's pelvis yet ("floating presenting part"). This prolapse can occur, too, if the amniotic sac breaks before the fetus has moved into place in the pelvis.
Umbilical cord prolapse is an emergency. If you are not at the hospital when it happens, call an ambulance to take you there. Until help arrives, get on your hands and knees with your chest on the floor and your buttocks raised. In this position, gravity will help keep the baby from pressing against the cord and cutting off his or her blood and oxygen supply. Once you get to the hospital, a cesarean delivery will probably be performed unless a vaginal birth is already progressing naturally.
Umbilical Cord Compression
Umbilical cord compression can occur if the cord becomes wrapped around the baby's neck or if it is positioned between the baby's head and the mother's pelvic bone. You may be given oxygen to increase the amount available to your baby. Your doctor may hurry along the delivery by using forceps or vacuum assistance, or in some cases, delivering the baby by cesarean section.