Preterm labor is one of the most important and vexing challenges complicating pregnancy. Premature babies account for an estimated 6%–10% of births, yet they account for 70%–85% of neonatal morbidity and mortality.
In multiple gestations, which are increasingly common as a result of delayed childbearing and the use of assisted reproductive technologies, preterm labor is an even greater risk. The literature points to an incidence of preterm labor of 20%–75% in multiple gestations. Although these figures may be somewhat high, I think it is safe to say that at least 1 in 10 multiple gestations seen at my institution are complicated by preterm labor. Not all of these patients will be admitted or will deliver early, but the very common nature of this problem and the potentially lethal consequences of premature multiple deliveries make this an issue that every physician and institution should approach carefully.
First, it is important to consider the delivery goal of a multiple gestation pregnancy. Overall, most twins are delivered at 37–38 weeks. For triplets, the gestational age is closer to 34 weeks, and quadruplets are born at around 30 weeks. These are reasonable numbers applicable to community practice.
If a patient arrives in preterm labor, you have to decide what to do, considering her situation and the capabilities of your local hospital and medical staff. It is clear that premature babies fare best when they are cared for in the institution where they are born. If someone needs to be transferred, it should be the mother, not the baby.
Obviously, if a patient carrying twins presents in labor at 35 or 36 weeks, most obstetricians would be inclined to do very little to cut short the labor, because—in the absence of other complications—these babies are likely to do well. However, if she presents at 29 weeks, it would make sense to be more aggressive.
Can the patient be safely and aggressively managed for preterm labor in her local community? The answer hinges on the plan for delivery if the treatment fails. Each hospital and service has to pick a gestational age at which neonatal survival is acceptably high. Then, options for the mother should be discussed with her and with the neonatal intensive care unit at your hospital or the institution to which she will be transferred.
Depending on the circumstances, the treatment of preterm labor may be undertaken for several reasons:
▸ To delay delivery until the patient can be transferred to a tertiary medical center with a high-level neonatal intensive care unit.
▸ To delay delivery 24–48 hours for the administration of corticosteroid therapy.
▸ To reduce the strength and frequency of uterine contractions, enabling the fetus to further develop in the uterus.
▸ To minimize hospital stays for the mother and the neonate.
▸ To reduce the risk of neonatal morbidity and mortality by preventing preterm delivery, the most dangerous complication of multiple gestation pregnancies.
When I consult with a woman in preterm labor, I go through a list of available options. Unfortunately, a careful review of the literature reveals few really good, effective treatments.
Although new ideas emerge every few years, not many interventional strategies have withstood attempts to corroborate results from single institutions. It may be tempting to “just do something,” but we owe it to our patients to stick to scientifically valid and efficacious treatments.
Bed rest or activity restriction will not prevent preterm labor. Rest neither lengthens gestation nor reduces neonatal morbidity in multiple gestation pregnancies. In some studies these patients did worse.
If a patient carrying multiples has a short cervix and threatened preterm labor, there is some evidence to support getting her off her feet rather than having her continue working at a very active job.
Once a multiple pregnancy is complicated by preterm labor, hospitalization may be necessary for observation and implementation of a treatment course.
There is no evidence that hydration is an effective treatment for preterm labor. In fact, the initial administration of bolus intravenous fluids may pose some risk to patients with multiple gestations. These patients already have an increased blood volume and could develop pulmonary edema from fluid overload if tocolytic therapy is initiated after unnecessary fluids are administered.
A study by Paul J. Meis, M.D., and colleagues (N. Engl. J. Med. 2003;348:2379–85) suggests recurrent preterm birth in singleton pregnancies can be prevented by 17 δ-hydroxyprogesterone caproate. The jury is still out on whether progesterone can be useful in managing active or threatened preterm labor in a multiple gestation pregnancy.