Why steroids are recommended for preterm labor

Steroid shots help speed up the development of your baby's lungs, which greatly increases your premature baby's chances of survival. That's why they're recommended by the National Institutes of Health (NIH) and the American College of Obstetricians and Gynecologists (ACOG).

If you're between 24 and 34 weeks pregnant and likely to deliver a premature baby in the next week, both the NIH and ACOG recommend a single course of antenatal corticosteroids (ACS). (This is a type of steroid that crosses the placenta better than other types.) In certain cases, ACS can be given between 34 and 36 weeks.

Your doctor may recommend the treatment if you're having symptoms of preterm labor, for example, or if you've been admitted to the hospital for a condition that may (or is scheduled to) result in an early delivery, such as preterm premature rupture of membranes (PPROM), cholestasis of pregnancy, or early preeclampsia.

Antenatal corticosteroids include the medications betamethasone (Celestone) and dexamethasone (Decadron). Both are given as injections, usually in the hospital. If you receive betamethasone (the more commonly used of the two), you'll be given two doses, 24 hours apart. Dexamethasone is given in four doses, 12 hours apart.  

Your practitioner may consider giving you a second treatment, however, if your last treatment was more than two weeks ago, you're still less than 34 weeks pregnant, and you're likely to deliver within the next seven days. This repeat course of steroids is called a rescue course.

Having more than two courses of corticosteroids isn't recommended. While research is ongoing, some studies have found negative effects of repeated (three or more) ACS courses, including a reduction in the baby's birth weight and head circumference.

You may also receive medication called tocolytics if you're showing signs of preterm labor. This medication can help slow or stop contractions, delaying labor for a few days so that you can receive ACS treatment. You may also receive antibiotics to kill any bacterial infections – if you have a positive Group B strep test, for example, or if you have PPROM.  

How long after steroid injections can my baby be born?

The maximum benefits of steroid injections begin when your baby is born two to seven days after receiving the first dose. The treatment isn't as effective if you deliver less than 24 hours from the time you receive the first dose, and it becomes less effective after 7 days. Your doctor will try to give you the treatment at the best time, based on when they think your baby will be born.

Still, the treatment begins working as early as six hours after the first injection, and babies who deliver before the second dose have better outcomes than those not receiving any treatment.

Benefits of steroid shots

ACS treatment speeds up your baby's lung development by prompting the cells in the lungs to produce a chemical called surfactant. Surfactant is normally produced by lung tissue in the mid- to-late third trimester. This surfactant production helps accelerate lung maturation and prevents neonatal respiratory distress syndrome (RDS) which affects a baby's breathing.

Steroid shots also reduce the chance your baby will have some other health problems, such as:

• Neonatal mortality (death) in the first 48 hours
• Bleeding in the brain, or intraventricular hemorrhage (IVH)
• Systemic infection
• Necrotizing enterocolitis (NEC), which affects a baby's intestines

Risks of steroid injections in pregnancy

Corticosteroids appear safe for moms and their babies, and, with few exceptions, the benefits are thought to outweigh any possible problems.

Researchers continue to study possible risks linked to ACS treatment, but to date most studies show no adverse effects on the growth or development of babies or children whose mothers received a single course of ACS before 34 weeks of gestation.

In an effort to examine long-term effects, some researchers looked at adults (around 31 years of age) whose mothers took one course of betamethasone during pregnancy and found no effects on cognitive functioning, working memory and attention, or health-related quality of life.

For the vast majority of moms-to-be, steroids won't have any adverse effects on pregnancy. However, a single dose of steroids may cause a temporary rise in blood sugar (glucose). If you have diabetes or gestational diabetes, you may need to increase your insulin dosage if you take corticosteroids. Your practitioner will monitor you closely.

Learn more:

• What to know about premature babies' survival rates and health outcomes
• Preterm labor test: Fetal fibronectin
• Your preemie baby's growth and development