Betamethasone: In-Utero Steroids Help Prevent Birth Injuries in Premature Babies

Premature babies are at risk for serious health problems, including respiratory distress, brain bleeds, periventricular leukomalacia (white matter brain damage), and necrotizing enterocolitis (intestinal infection). If physicians expect that an infant is going to be born preterm, they can lessen these risks by injecting the pregnant mother with a drug called betamethasone. Betamethasone can help the baby’s organs and tissues mature faster, which decreases vulnerability to the aforementioned issues and improves long-term health outcomes.

Betamethasone is a type of corticosteroid, which are synthetic versions of naturally-occurring hormones. In adults, corticosteroids can be used to reduce itching, swelling, and allergic reactions. Betamethasone can also be given in utero (antenatally) via an injection into the mother’s arm, leg, or buttocks; it then travels through her bloodstream and into the baby’s circulation (1). Antenatal betamethasone is primarily used to speed up lung development in preterm fetuses. It stimulates the synthesis and release of surfactant (2), which lubricates the lungs, allowing the air sacs to slide against one another without sticking when the infant breathes. Full-term babies produce enough surfactant to breathe without assistance, but premature babies often do not. Antenatal betamethasone can help to mitigate this issue, and it significantly reduces the risk of serious respiratory problems and death (3).

In addition to preparing the baby’s lungs for the outside world, betamethasone reduces the risk of infant brain bleeds and a type of intestinal infection called necrotizing enterocolitis (3, 4). One meta-analysis indicated that betamethasone  could prevent brain bleeds in about six of 100 babies and necrotizing enterocolitis in about four of 100 babies (4).

Overall, antenatal betamethasone may reduce a premature infant’s chance of death by as much as 40 percent (1, 5). Moreover, it can decrease the risk of lifelong disabilities such as periventricular leukomalacia (2), cerebral palsy (CP) (6), seizures, and intellectual disabilities, among other issues.

Animal studies have shown significant risks associated with antenatal betamethasone, including hyperactivity, other behavioral abnormalities, and altered endocrine function. Moreover, in guinea pigs, it is not just the direct offspring that are affected; the consequences of betamethasone can continue on to the next generation. Researchers believe this is due to epigenetic mechanisms; in other words, changes in DNA expression that can be heritable (5, 7).

Although these findings were somewhat alarming, research on humans has indicated that when given late in pregnancy and in small doses, the risks are minimal (1, 2, 8). Women at high risk of delivering prematurely used to receive steroids once a week until their babies were born. However, studies linked multiple courses of steroids with lower birth weights and smaller heads (1, 8, 9), so repeated courses are no longer recommended, in most cases.

The American College of Obstetricians and Gynecologists (ACOG) currently makes the following recommendations regarding corticosteroid administration:

• Women between 24-34 weeks of gestation, who are at risk of delivering a premature baby within the next week, should be given a single course of corticosteroids. In some cases, this may also be recommended for women between 23-24 weeks of pregnancy.
• Women between 34-37 weeks of gestation, who are at risk of delivering a premature baby within the next week, can be given a single course of corticosteroids if they have not already received one.
• Women at less than 34 weeks of gestation who are at risk of delivering a premature baby within the next week can be given a second course of course of corticosteroids if it has been more than 14 days since the first course. In some situations, physicians may recommend a second course seven days after the first (8).

Betamethasone is most effective if given between two and seven days prior to the baby’s birth (1).

Besides giving antenatal betamethasone, there are other things doctors may recommend in order to help a fetus that is likely to be born prematurely or a baby that already has. These interventions include:

1. Cervical cerclage to prevent preterm birth in women with incompetent cervix
2. Progesterone therapy to prevent preterm birth
3. Medications to stop contractions (terbutaline and brethine)
4. Antenatal magnesium sulfate to protect the baby from brain injuries
5. Surfactant given to the baby after birth
6. Careful monitoring for and prevention of infection
7. Ventilatory and respiratory support

For more information, please visit our page on “Premature Birth and Its Prevention.”