Twins: Why are twins often born early?

I am pregnant with twins. I have carried my two other babies past term and they were good-sized babies and very healthy. I attribute this to my excellent diet. My doctor told me not to expect a full-term birth this time and that twins were often born early. Is this always true, and if so, why?

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Peg Plumbo CNM

Peg Plumbo has been a certified nurse-midwife (CNM) since 1976. She has assisted at over 1,000 births and currently teaches in the... Read more

A twin, or any other higher order multifetal gestation, is by its nature a higher risk pregnancy. The most frequently encountered problem with a twin gestation is prematurity. Growth restriction is another difficulty that may be experienced by one or both of the fetuses. Some labors need to be induced before term if one or both of the babies is in jeopardy.

Because we don't precisely know why labor starts in singleton pregnancies, it is hard to accurately theorize what influences preterm labor in twin gestations.

The distended uterus may put out signals or respond to hormones triggering premature contractions. The amniotic membranes may rupture too early. We know that the fetus has a role in the initiation of labor, so if two or more fetuses are present, perhaps they secrete a higher level of a stimulus substance. We just don't know the answer or answers.

Some twins share the same placenta and the same amniotic membranes (monoamniotic). These twins are at higher risk of cord entanglement and of twin to twin transfusion. Such a pregnancy is considered "full term" at 34 weeks and should be delivered this early because of the significantly higher risks associated with longer gestation.

All twin gestation are considered full term at 38 weeks by most obstetricians and it is not unusual for mothers to be induced at this time. Risks of going to term with twins are: the potential for cord prolapse, intrauterine fetal death of one baby and twin to twin transfusion. Mothers too may be at higher risk of placental abruption, hemorrhage and hypertension.

A report was published recently by the Health Resources and Services Administration's Maternal and Child Health Bureau (The Journal of the American Medical Association, 2000;283). Lead author, Dr. Michael D. Kogan, reported that results demonstrated that mothers who received more frequent prenatal visits had the highest risk of preterm birth, but these babies were more likely to survive.

Might it be that women who seek prenatal care earlier and are more adherent to a schedule of regular visits are higher risk, or are the interventions and antepartal fetal testing creating the need to deliver these babies earlier?

The number of twin gestations has increased as maternal age has advanced and assisted reproductive therapies are utiized more frequently. Such women are seeking care from, and are being referred more often to, higher level specialists. Such practitioners rely on technology to ascertain fetal well-being. The results may be earlier and earlier delivery. Fear of litigation may also be driving such preterm interventions and deliveries.

The message is clear that women need to regain some of the faith in their own ability to birth their babies. Mothers and fathers should interview potential care providers to see if philosophies match. Trust in one's physician or midwife is critical as is the ability and freedom to ask questions and even disagree with the plan of care. Such a dialogue is in the best interests of the woman, her baby and the family.

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