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MULTIPLE GESTATION

Multiple gestation refers to a pregnancy in which two or more fetuses are present in the womb. Generally this occurs in approximately 1 to 2 percent of pregnancies. However, with the use of fertility drugs and high-tech procedures such as in vitro fertilization (IVF), multiple gestations are much more common. The vast majority of these pregnancies are twins, but triplets, quadruplets, and higher numbers can occur.

Because multiple pregnancies have a shorter gestation period, babies are at risk of premature birth and other complications such as increased chance of miscarriage, birth defects, premature birth, and mental and/or physical problems. In general the risk of complications due to premature delivery is significantly less once the pregnancy reaches 32-34 weeks gestation.

The average length of pregnancy is:

• 39 weeks for a single gestation
• 35 weeks for twins
• 33 weeks for triplets
• 29 weeks for quadruplets

Maternal risks due to multiple gestation include premature labor, premature delivery, pregnancy-induced high blood pressure or pre-eclampsia (toxemia), diabetes, and vaginal/uterine hemorrhage.

Diagnosis of Multiple Gestation

Multiple gestation is usually diagnosed before delivery accurately and safely by using a combination of ultrasound (using sound waves to create an image of your baby) examination, and a blood test for alpha-fetoprotein.

Prenatal Care

A multiple pregnancy requires special prenatal care, with more prenatal visits and medical tests than normal pregnancies. In addition, the risk of certain complications is higher in multiple gestation. The mother is more likely to develop high blood pressure or anemia, and the babies are more likely to be born small. The mother is also more likely to go into preterm labor. Sometimes these problems can be prevented with early detection and proper prenatal care.

Nutrition

Multiple gestation is a major nutritional stress. Some of the key nutrients that need to be included in a multiples pregnancy diet are adequate amounts of protein, calories, calcium and iron.

Eating well and gaining weight are important for the health of the mother and her children. Experts suggest the mother should add an estimated 300 calories per baby to her daily diet.

Prenatal vitamins with folic acid are prescribed to help babies grow and protect against birth defects. In multiple gestation anemia is common, therefore it is especially important to take prenatal vitamins and iron as prescribed. Anemia results from inadequate iron supply which can cause loss of appetite, extreme fatigue in the mother as well as decreased oxygen supply to the babies.

Calcium is also very important during the last two trimesters. The last trimester is when half the calcium required by the fetus will be deposited in the fetal bones. The required amount of calcium is 1,600-2,000 mg. per day for a multiple pregnancy.

Rest

The uterus becomes much larger than normal in multiple gestation, often causing more discomfort than a normal pregnancy. Doctors recommend resting during the day for more energy, avoiding standing for long periods and lifting heavy objects.

With the increased risk of complications associated with a multiple birth, bedrest may be recommended at some point during the pregnancy to alleviate potential health risks to the mother (such as pre-eclampsia), or for the babies (such as preterm labor).

Multiple Gestation Complications

Premature Labor Premature labor is the onset of true labor before the 37th week of gestation (3 weeks before the due date). Premature labor can result in premature birth, the most common problem of multiple gestation. This condition occurs ten times more often in multiples than with singletons. About half of all twins and three-quarters of triplets are born before the thirty-seventh week of pregnancy. Premature babies often have respiratory and digestive problems.

If premature labor starts, but then is stopped and the baby is delivered at term, the baby is at no increased risk for complications. If the premature labor results in delivery, however, the complications expected depend on the baby's age, weight, and general condition.

Warning Signs of Preterm Labor

• Discharge from your vagina: Change in type (watery, bloody or mucous)/increase in amount
• A feeling of pressure in your lower abdomen or pelvic area
• Constant, low, dull backache
• Mild abdominal cramps like a menstrual period, with or without diarrhea
• Regular contractions or tightening of your uterus
• Ruptured membranes (your "water breaks")
• "Feeling bad or something's not quite right"

A physician should be contacted immediately if premature labor is suspected.

Hypertension

High blood pressure that occurs for the first time in pregnancy is called pregnancy-induced hypertension. Although this condition is seen more often in multiple pregnancies, the diagnosis and treatment is the same as when carrying a single baby.

Usually a slightly elevated blood pressure causes no harm to mother or baby. However, if mildly elevated blood pressure is accompanied by protein in the urine, swelling in the hands and face, or changes in certain blood tests, the diagnosis is pre-eclampsia.

Many women have some swelling, especially in their feet and legs, at the end of the day. Too much or sudden swelling may be more serious. The symptoms of pre-eclampsia are different for each patient, but in rare, severe cases, they can include seizures ("eclampsia") or temporary liver or kidney dysfunction. Very high blood pressures can lead to a stroke. This level of hypertension is quite rare in pregnant women who have not had prior blood pressure problems.

Those with multiple pregnancies should contact their physicians immediately if they experience any of the following warning symptoms of hypertension:

• Swelling in your hands or feet
• Sudden weight gain (5 pounds in one week)
• Persistent headache
• Constant spots before your eyes/blurred vision
• Pain in the upper abdomen

When blood pressure elevates during pregnancy bed rest may be recommended and/or hospitalization may even be required. If blood pressure becomes too high delivery may be necessary. Upon delivery symptoms of this condition usually resolve quickly. Blood pressure may take a few weeks to return to normal, but the patient is usually out of the dangerous zone before they leave the hospital.

Growth Problems

Since multiples have to share the nutrition they receive, one or both babies might grow at a slower rate than expected or have other growth problems. Intrauterine growth restriction (IUGR) is the term for slow growth of babies during pregnancy.

Twins are called discordant if one is much smaller than the other. This may be due to one twin getting more blood and having more amniotic fluid than the other, poor functioning of the placenta, or birth defects. The smaller baby is more likely to have problems during pregnancy and after birth. Ultrasound will be used to check each baby's growth and the amount of amniotic fluid. Early delivery may be needed if either baby shows signs of having problems before term.

One condition that can cause one twin to be smaller than the other is twin-twin transfusion syndrome (TTS). TTS can develop when twins share a placenta. It affects identical twins during pregnancy when blood passes disproportionately from one baby to the other through connecting blood vessels within their shared placenta. This can be dangerous for both twins. One baby, the recipient twin, gets too much blood overloading his or her cardiovascular system, and may die from heart failure. The other baby, the donor twin, does not get enough blood and may die from severe anemia.

An ultrasound is used to check the amount of amniotic fluid. Some of the extra fluid may need to be removed. If TTS is severe, the twins may have to be delivered early.

Ultrasounds are generally performed in the last few months of pregnancy in order to follow the growth of each baby.

Fetal Loss

Sometimes one baby will miscarry, leaving the others to develop on their own. In early pregnancy, this is called the vanishing twin. If this happens, you may have some spotting or bleeding from your vagina. This does not harm you or the other baby. Death of one of the babies is more serious in later pregnancy.

Monitoring Multiple Gestation

Many techniques are used to check the well-being of multiples. They may be done to confirm other test results or to provide further information. Tests administered during multiple gestation include:

• Repeat ultrasound to check the babies' growth
• Examine your cervix for changes that may show early signs of preterm labor
• Count your babies' movements, called kick counts
• Examine the babies' heart rate, body movement, muscle tone, and the amount of amniotic fluid by ultrasound
• Measure the babies' heart rate in response to the their own movements (called a nonstress test)
• Amniocentesis may be needed to reveal the babies' lung maturity

Delivery

The delivery of multiples depends on certain factors:

• Position of each baby
• Weight of each baby
• Health of the mother
• Health of the babies

The main deciding factor in delivery method is the position of the baby closest to the cervix. Twins can usually be born vaginally if they are both are in the head-down position. A vaginal birth may also be possible if the first twin is born vaginally and the second one is breech or sideways. The obstetrician may accomplish this by moving the second twin into a better position by pushing on the mother's abdomen externally or performing a breech extraction.

If these methods don't work, a cesarean birth may be needed, in which the baby is delivered through a cut made in the abdomen and uterus. When the lower twin is not in the head-down position, both twins often are delivered by cesarean birth. Cesarean delivery may also be needed when either of the babies is having problems.

Since fetal positions are often not head down, the vast majority of triplets and larger multiples are delivered by cesarean section.

Labor may take longer with multiples, especially the pushing stage. Babies are usually born several minutes apart in a vaginal delivery, but it can take longer.

Thomas G. Stovall, M.D.

Dr. Stovall is a Clinical Professor of Obstetrics and Gynecology at the University of Tennessee Health Science Center in Memphis, Tennessee and Partner of Women's Health Specialists, Inc.

Date Published: 2004-03-10

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