What Might Go Wrong in the Third Trimester?

Written by the Healthline Editorial Team | Published on March 15, 2012
Medically Reviewed by Joan Lingen, Department of Obstetrics and Gynecology, Onley Community Health Center, Onancock, VA

Overview

Prenatal care is especially important in the third trimester because the types of complications that can arise at this time are more easily managed if detected early.

Gestational Diabetes

Gestational diabetes occurs because the hormonal changes of pregnancy make it more difficult for your body to effectively use insulin. When insulin cannot do its job of lowering blood sugar to normal levels, the result is abnormally high glucose (blood sugar) levels. Most women have no symptoms. While this condition is usually not dangerous for the mother, it poses several problems for the fetus. Specifically, macrosomia (excessive growth) of the fetus can increase the likelihood of cesarean delivery and the risk of birth injuries. When glucose levels are well controlled, macrosomia is less likely.

At the beginning of the third trimester, all pregnant women should get tested for gestational diabetes. During this test (the so-called one-hour glucose test) a woman drinks a glucose-laden fluid, and her blood sugar level is tested one hour later. If it is abnormal (above 130 or 140mg/dL based on which of two accepted standards is used), a three-hour oral glucose tolerance test (OGTT) is done to confirm the diagnosis. Prior to this test, a woman follows a carbohydrate diet for three days and then fasts overnight (eight hours). She then takes 100 mg of oral glucose. Her glucose levels are measured before she drinks the glucose solution, and then at one, two, and three hours afterwards. The diagnosis of gestational diabetes can be made if two or more values are elevated. Normal plasma glucose levels are 95 or 105 (fasting), 180 or 190 (one hour after glucose solution), 155 or 165 (after two hours), and 140 or 145 (after three hours). This confirmatory test is often negative. If the test is abnormal, dietary changes, exercise, and possibly insulin (Humulin N, Humulin R) will be needed to bring the glucose levels into normal range.

The good news is that gestational diabetes usually resolves during the postpartum period, but there is up to a 50% chance of developing diabetes later in life which can be decreased through lifestyle modifications like diet and weight control. It is also important to note that gestational diabetes will often complicate future pregnancies requiring careful attention to diet, weight control, and usually an early one hour glucose tolerance test. In the event that high glucose levels continue for six weeks after postpartum, the patient will be diagnosed with underlying diabetes mellitus.

Preeclampsia

Preeclampsia is a condition characterized by high blood pressure, protein in the urine, and swelling of the hands and face that occurs after 20 weeks of pregnancy. It occurs in about 10 to 15% of pregnancies and is more common with the first pregnancy, in teenagers, and in women over 35. While it can occur in the late second trimester, preeclampsia is much more common in the third trimester, near term. Preeclampsia can lead to eclampsia (seizures), kidney failure, and rarely death in the mother and fetus.

Signs and Symptoms

Warning Signs 

The Family & Medical Leave Act: If you develop rapid swelling of your feet and legs, hands, or face or any of the following symptoms, call your doctor:

  • headache that does not go away with acetaminophen (Tylenol);
  • loss of vision;
  • "floaters" in your vision;
  • severe pain on your right side or in your stomach area; or
  • easy bruising.

Many women have no symptoms at first. Others have headaches, vision changes, and upper abdominal pain. These signs may suggest severepreeclampsia. The first sign that your doctor usually sees is high blood pressure during a routine prenatal visit. Protein may be detected in your urine, and you may have gained excessive weight. Sometimes your hands and face are swollen, but this is frequently absent in mild disease. Blood tests, such as liver and kidney function tests and blood clotting tests, may confirm the diagnosis and can detect severe disease.

Treatment

How your doctor treats preeclampsia depends on its severity and how far along in the pregnancy you are, but delivery is the ultimate treatment.

  • Inducing labor is recommended for term pregnancies and for preterm pregnancies that are unstable or in which the baby's lungsare mature.
  • If you develop mild preeclampsia long before your due date, your doctor may monitor you and the fetus and allow the fetus to mature more. If you are near term, if the baby's lungs are mature, or if severe disease develops, labor is induced. All women with preeclampsia should be put on magnesium sulfate therapy during labor and after delivery for about 24 hours to reduce the risk of seizures.
  • If severe preeclampsia occurs when the fetus is very preterm (about 24 to 32 weeks), your doctor may try to prolong your pregnancy to allow fetal growth. You are hospitalized, monitored carefully, and given steroids to help mature the baby's lungs. If your doctor sees signs of worsening disease, she might induce labor or deliver your baby by cesarean section. Magnesium sulfate is also used to help prevent seizures. In severe preeclampsia, your doctor will focus on preventing eclampsia, controlling blood pressure, and delivering the baby.

Preeclampsia rapidly disappears after delivery. In rare cases, a woman needs blood pressure medication for a short time or diuretics to treat pulmonary edema (fluid in the lungs). While preeclampsia is primarily a disease of first pregnancies, there is an increased risk of recurrence with future pregnancies.

Cause and Prevention

Despite years of scientific study, the true cause of preeclampsia is not known, nor is there any effective prevention. The cure, however, has been known for many decades, and that is delivery of the baby. For that reason, timely diagnosis and delivery is the best way to avoid serious problems for the mother and for the fetus.

Preterm Labor

When labor occurs before the 37th week of pregnancy (before the ninth month), it is considered preterm. Preterm labor is more common in women with a previous preterm birth, with multiple-birth pregnancies (twins, triplets, etc.), with excess amniotic fluid (polyhydramnios), or with infection of the amniotic sac (amnionitis).

Symptoms

The signs and symptoms of preterm labor may be subtle and include vaginal pressure, low back pain, frequent urination, diarrhea, increasedvaginal discharge, or tightness in your lower stomach. In other cases the symptoms are more obvious and you will experience regular painful contractions, leaking of fluid from the vagina, or vaginal bleeding.

Treatment

Premature infants are at risk for numerous health problems - lung disease, in particular. Those risks are much higher for the very preterm infant (24 to 28 weeks of gestation). The exact cause of premature labor is not understood, but it is important for you to be cared for as soon as possible. Several strong medications, such as magnesium sulfate, can help stop preterm labor and delay delivery. Each day your pregnancy is prolonged increases your chances for a healthy baby. A steroid medication is often given to the mother if preterm labor occurs before 34 weeks. This helps mature the fetus's lungs and reduces the severity of lung disease if your labor cannot be stopped. This medication has its peak effect within two days, so it is best to prevent delivery for at least two days, if possible.

All women with preterm labor who have not been tested for the presence of Group B streptococcus should receive antibiotics (penicillin G, ampicillin, or an alternative for those who are penicillin allergic) until delivery.

If preterm labor begins after 36 weeks, the baby is usually delivered, since the risk of lung disease from prematurity is very low.

Preterm Premature Rupture of Membranes (PPROM)

Rupture of membranes is a normal part of giving birth. It is the medical term for saying ?your water broke.? This means that the amniotic sac that surrounds your baby has broken, allowing the amniotic fluid to flow out.

While it is normal for the sac to break during labor, if it happens too early it can cause serious problems for your baby. This is called preterm premature rupture of membranes, or PPROM. Although the cause of PPROM is not clear, infection of the amniotic membranes may be an underlying problem in many cases.

Treatment

Treatment for PPROM varies. Women are often hospitalized and given antibiotics, steroids, and drugs to stop labor (tocolytics). When PPROM occurs at 34 weeks or more, some doctors recommend inducing labor, since the risks of prematurity to the fetus may now be less than the risk of developing serious infection in the fetus or uterus. If there are signs of infection, labor must be induced to avoid serious complications.

Many women deliver within two days of rupture. Within a week almost all women deliver their babies. Occasionally, a woman with PPROM experiences resealing of the membranes. In these rare cases, she may continue her pregnancy to near term, but is watched closely for signs of infection.

Risks of prematurity decrease significantly as the fetus nears term. If PPROM occurs in the range of 32 to 34 weeks and the remaining amniotic fluid shows that the fetus' lungs have matured enough, some physicians induce labor. With improved intensive care nursery services, many preterm infants born in the third trimester (after 28 weeks) do very well.

Problems with the Placenta (Previa and Abruption)

Bleeding in the third trimester may have several causes. A common cause is the normal bleeding associated with labor, which is usually limited and not dangerous. Other serious causes of bleeding are placenta previa and placental abruption.

Placenta Previa

Placenta previa is the abnormal implantation of the placenta over the cervical opening (cervical os). The exact cause of this condition is not understood, but it is more common in women who have had a previous cesarean delivery or previous uterine surgery. Other predisposing factors include large placentas and smoking. This condition is serious because of the risk of bleeding before or during delivery. This can be life-threatening to both the mother and baby.

A common symptom of placenta previa is bright red, sudden, profuse, and painless vaginal bleeding, which usually occurs after the 28th week of pregnancy. An ultrasound is about 95% accurate in determining whether placenta previa is present.

Treatment depends on whether the fetus is preterm and on the amount of bleeding. If labor is unstoppable, the baby is in distress, or there is life-threatening hemorrhage, immediate cesarean section is indicated, no matter how old the fetus is. If the bleeding stops or is not too heavy, delivery can often be avoided to allow the preterm fetus to grow more. If the fetus is near-term or term, delivery usually is recommended. Delivery by cesarean section is necessary. Because of modern obstetric care, ultrasound diagnosis, and the availability of transfusion, if needed, women with placenta previa and their infants usually do well.

Placental Abruption

Placental abruption is a condition in which the placenta separates from the uterus prior to labor. It occurs in less than 1% of births. Placental abruption can result in fetal death and can cause serious bleeding and shock in the mother. Predisposing factors for abruption include cocaine use, high blood pressure (hypertension), advanced maternal age, prior pregnancies, diabetes, uterine distension from excess amniotic fluid (polyhydramnios) or multiple pregnancy, smoking, and heavy alcohol use Precipitating factors include trauma (from a car accident or a blunt blow to the abdomen, for example), PPROM (preterm premature rupture of the membranes), sudden uterine volume loss, and a short umbilical cord.

Symptoms can range from no obvious symptoms in mild abruption to heavy vaginal bleeding and unrelenting abdominal pain from sustained uterine contractions with severe abruption. The uterus is often firm and tender. If a fetal heart tracing shows distress, rapid delivery may be recommended. If the mother has severe bleeding or clotting difficulties, rapid delivery may also be necessary. Cesarean section is frequently necessary. Blood transfusion is commonly needed in severe abruption.

Intrauterine Growth Restriction (IUGR)

Occasionally a baby will be small for gestational age, resulting in asymmetric growth (except in the brain). Maternal hypertension is a common cause since it prevents the placenta from delivering the optimum amount of oxygen and nutrients to the fetus. Other maternal factors that can lead to IUGR include anemia, severe malnutrition, severe diabetes, and chronic renal disease. Factors that limit blood flow to the placenta, like placental infarction and placenta previa, can also lead to IUGR.

Fetuses with IUGR may be less able to tolerate the stress of labor than infants of normal size.

IUGR babies tend to have less body fat and more trouble maintaining their body temperature and glucose levels (blood sugar) after birth.

If growth problems are suspected, an ultrasound is done to measure the fetus and calculate an estimated fetal weight. The estimate can be compared with the range of normal weights for fetuses of similar age. In order to determine whether the fetus is small for gestational age or growth restricted, a series of ultrasounds will be done over to time to document weight gain. A specialized ultrasound monitoring umbilical blood flow, which can be decreased in growth restricted fetuses, may also be ordered. Amniocentesis may be used to check for chromosomal problems or infection. Monitoring the fetal heart pattern and measurement of the amniotic fluid are common. Induction of labor or cesarean section for the preterm IUGR fetus may be necessary if growth stops, if there is reduced amniotic fluid, or if the fetus shows an abnormal heart rate.

Luckily, most growth-restricted babies develop normally after birth. They tend to catch up in growth by two years old.

Post-Term Pregnancy

Most women deliver between 38 and 42 weeks gestation. About 10% deliver after 42 weeks, which is considered post-term or post-dates.

Sometimes, a woman's due date is not calculated correctly, and the pregnancy is therefore not truly post-term. Early in pregnancy, an ultrasound can confirm the correct due date and eliminate the confusion. When good dating techniques are used, true post-term pregnancies only happen 2% of the time. The cause of post-term pregnancy is unclear, although hormonal and hereditary factors are suspected.

Post-term pregnancy is not generally dangerous to the mother's health. The concern is for the fetus. The placenta is an organ that is designed to work for about 40 weeks. It provides oxygen and nutrition for the growing fetus. After 41 weeks of pregnancy, the placenta is less likely to work well, and this may result in decreased amniotic fluid around the fetus (oligohydramnios). This condition can cause compression of the umbilical cord and decrease oxygen supply to the fetus. This may be reflected on the fetal heart monitor in a pattern called late decelerations. There is a risk of sudden fetal death when the pregnancy is post-term.

Once a woman reaches 41 weeks of pregnancy, she usually has fetal heart rate monitoring and a measurement of the amniotic fluid. If the testing shows low fluid level or abnormal fetal heart rate patterns, labor is induced. Otherwise, spontaneous labor is awaited until no more than 42 to 43 weeks, after which it is induced.

The other risk is meconium. Meconium is a fetus's bowel movement and it is more common when the pregnancy is post-term. Most fetuses that have a bowel movement inside the uterus have no problems. However, if the fetus inhales the meconium, it can cause a very serious type of pneumonia and rarely death. For these reasons, physicians have traditionally tried to wash out the meconium during labor with an amnioinfusion (instillation of fluids into the uterus through a tube passed up through the cervix). Immediately after delivery, the baby's nose and mouth are suctioned to remove meconium, and a doctor may pass a tube down into the baby's windpipe to remove it before it can reach the lungs. Unfortunately, recent studies have failed to confirm a benefit to these interventions.

Malpresentation (Breech, Transverse Lie)

As a woman approaches her ninth month of pregnancy, the fetus generally settles into a head down position inside the uterus. This is known as vertex or cephalic presentation. In about 3% of pregnancies, the fetus will be bottom or feet first, known as breech presentation. Occasionally, the fetus will be lying sideways (transverse presentation).

The safest way for a baby to be born is head first or in the vertex presentation. If the fetus is breech or transverse, the best way to avoid problems with delivery and prevent cesarean section is to try to turn (or vert) the fetus to vertex presentation (head down). This is known as external cephalic version and it is usually attempted at 37 to 38 weeks if the malpresentation is known.

External cephalic version is somewhat like a firm massage of the abdomen and can be uncomfortable. It is usually a safe procedure, but some rare complications include placental abruption and fetal distress, necessitating emergency cesarean section.

If the fetus is successfully turned, spontaneous labor can be awaited or labor can be induced. If the version is unsuccessful, some doctors wait a week and try again. If unsuccessful after reattempts, you and your doctor will decide the best type of delivery, vaginal or cesarean. Breech fetuses can be delivered vaginally or by cesarean section. Measurement of the bones of the mother's birth canal and ultrasound to estimate fetal weight are often obtained in preparation for breech vaginal deliveries. Transverse fetuses are delivered by cesarean.

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