Postterm pregnancy

Postterm pregnancy is the condition of a baby that has not yet been born after 42 weeks of gestation, two weeks beyond the normal 40.^[1] Post-mature births can carry risks for both the mother and the infant, including fetal malnutrition. After the 42nd week of gestation, the placenta, which supplies the baby with nutrients and oxygen from the mother, starts aging and will eventually fail. If the fetus passes its fecal matter, which is not typical until after birth, and breathes it in, it could become sick with meconium aspiration syndrome. Postterm pregnancy may be a reason to induce labor.^[2]

Signs and symptoms

Postmaturity symptoms vary. The most common are dry skin, overgrown nails, creases on the baby's palms and soles of their feet, minimal fat, a lot of hair on their head, and either a brown, green, or yellow discoloration of their skin. Doctors diagnose post-mature birth based on the baby's physical appearance and the length of the mother's pregnancy.^[3] Some postmature babies will show no or little sign of postmaturity.

Fetal and neonatal risks

• Reduced placental perfusion—Once a pregnancy has surpassed the 40-week gestation period, doctors closely monitor the mother for signs of placental deterioration. Toward the end of pregnancy, calcium is deposited on the walls of blood vessels, and proteins are deposited on the surface of the placenta, which changes the placenta. This limits the blood flow through the placenta and ultimately leads to placental insufficiency, and the baby is no longer properly nourished. Induced labor is strongly encouraged if this happens.
• Oligohydramnios
• Meconium aspiration

Maternal risks

• Large for gestational age:
• Increased incidence of forceps assisted, vacuum assisted or cesarean birth—Post-term babies may be larger than an average baby, thus increasing the length of labor. The labor is increased because the baby's head is too big to pass through the mother's pelvis. This is called cephalopelvic disproportion. Caesarean sections are encouraged if this happens.^[4] When post-mature babies are larger than average, forceps or vacuum delivery may be used to resolve the difficulties at the delivery time. Difficulty in delivering the shoulders, shoulder dystocia, becomes an increased risk.^[5]
• Increased psychological stress
• Probable labour induction
• Death (if the baby stayed for too long)

Causes

The causes of post-term births are unknown, but post-mature births are more likely when the mother has experienced a previous post-mature birth. Due dates are easily miscalculated when the mother is unsure of her last menstrual period. When there is a miscalculation, the baby could be delivered before or after the expected due date.^[6] Post-mature births can also be attributed to irregular menstrual cycles. When the menstrual period is irregular it is very difficult to judge when the ovaries would be available for fertilization and subsequent pregnancy. Some post-mature pregnancies are because the mother is not certain of her last period, so in reality the baby is not technically post-mature.^[2] However, in most countries where gestation is measured by ultrasound scan technology, this is less likely.

Monitoring

Once a baby is diagnosed post-mature, the mother should be offered additional monitoring as this can provide valuable clues that the baby's health is being maintained.

Fetal movement recording

Regular movements of the baby is the best sign indicating that it is still in good health. The mother should keep a "kick-chart" to record the movements of her baby. A rate of fewer than 10 movements in 2 hours is not a good sign, and a doctor should be contacted. If there is a reduction in the number of movements it could indicate placental deterioration.

Electronic fetal monitoring

Electronic fetal monitoring uses a cardiotocograph to check the baby's heartbeat and is typically monitored over a 30-minute period. If the heartbeat proves to be normal, the doctor will not usually suggest induced labor.

Ultrasound scan

An ultrasound scan evaluates the amount of amniotic fluid around the baby. If the placenta is deteriorating, then the amount of fluid will be low, and induced labor is highly recommended. However, ultra sounds are not always accurate since they also monitor the fetus's development, and if the fetus is smaller than normal, the doctor's guess at the age can be quite off. The actual placenta won't start to deteriorate until about 46 weeks. Because of the risks, doctors favour induction by 42 weeks.

Biophysical profile

A biophysical profile checks for the baby's heart rate, muscle tone, movement, breathing, and the amount of amniotic fluid surrounding the baby.

Doppler flow study

Doppler flow study is a type of ultrasound that measures the amount of blood flowing in and out of the placenta.^[5]

Management

Expectant

A woman who has reached 42 weeks of pregnancy is likely to be offered induction of labour. Alternatively, she can choose expectant management, that is, she waits for the natural onset of labour. Women opting for expectant management may also choose to carry on with additional monitoring of their baby, with regular CTG, ultrasound, and biophysical profile. Risks of expectant management vary between studies.^[7]

Inducing labor

Inducing labor artificially starts the labor process by using medication and other techniques. Labor is usually only induced if there is potential danger on the mother or child.^[8] There are several reasons for labor induction; the mother's water breaks, and contractions have not started, the child is post-mature, the mother has diabetes or high blood pressure, or there is not enough amniotic fluid around the baby.^[9] Labor induction is not always the best choice because it has its own risks. Sometimes mothers will request to be induced for reasons that are not medical. This is called an elective induction. Doctors try to avoid inducing labor unless it is completely necessary.^[8]

Procedure

There are four common methods of starting contractions. The four most common are stripping the membranes, breaking the mother's water, giving the hormone prostaglandin, and giving the synthetic hormone pitocin. Stripping the membranes doesn't work for all women, but can for most. A doctor inserts a finger into the mother's cervix and moves it around to separate the membrane connecting the amniotic sac, which houses the baby, from the walls of the uterus. Once this membrane is stripped, the hormone prostaglandin is naturally released into the mother's body and initiates contractions.^[8] Most of the time doing this only once will not immediately start labor. It may have to be done several times before the stimulant hormone is released, and contractions start.^[10] The next method is breaking the mother's water, which is also referred to as an amniotomy. The doctor uses a plastic hook to break the membrane and rupture the amniotic sac. Within a few hours labor usually begins. Giving the hormone prostagladin ripens the cervix, meaning the cervix softens, thins out, or dilates. The drug Cervidil is administered by mouth in tablet form or in gel form as an insert. This is most often done in the hospital overnight. The hormone oxytocin is usually given in the synthetic form of Pitocin. It is administered through an IV throughout the labor process. This hormone stimulates contractions. Pitocin is also used to "restart" labor when it's lagging.

The use of misoprostol is also allowed, but close monitoring of the mother is required.

Feelings

• Stripping the membranes: Stripping the membranes only takes a few minutes and causes a few intense cramps. Many women report a feeling similar to urination, others report it to be quite painful.
• Breaking the water: Having one's water broken feels like a slight tug and then a warm flow of liquid.
• Pitocin: When the synthetic hormone, pitocin, is used, contractions occur more frequently than a natural occurring birth; they are also more intense.

Epidemiology

Postterm pregnancy occurs in 3% to 12% of pregnancies.^[11]

Notes