Betamethasone is an injectable medication given during pregnancy, primarily to women at risk of preterm birth. This corticosteroid mimics naturally occurring hormones and helps prepare the unborn baby for an early arrival. Administering betamethasone improves outcomes for infants born prematurely.
Purpose of the Injection
The primary purpose of betamethasone during pregnancy is to accelerate the development of the baby’s lungs. Premature babies often have underdeveloped lungs, lacking sufficient surfactant—a substance that helps air sacs expand and prevents collapse. Betamethasone stimulates surfactant production, allowing lungs to function more effectively at birth.
This corticosteroid also promotes overall structural maturation of the lungs. It enhances the expression of surfactant-associated proteins and improves gas exchange and lung compliance. These actions prepare the fetal lungs for breathing outside the womb, which is especially important for infants born before their lungs are fully mature.
When and How it’s Administered
Betamethasone injections are typically recommended for pregnant women between 24 and 34 weeks of gestation at risk of preterm delivery within seven days. It may also be considered for women between 34 and 36 weeks and 6 days of gestation with a high risk of preterm birth. The standard dosage is two 12-milligram (mg) doses, administered intramuscularly, usually 24 hours apart.
Injections are given in a large muscle, such as the arm, leg, or buttocks, allowing the medication to reach the baby via the mother’s bloodstream. While a 24-hour interval is standard, shorter intervals, such as 12 hours, are being explored when delivery is imminent.
Benefits for the Baby
The primary benefit of betamethasone for the baby is a significant reduction in the risk and severity of respiratory distress syndrome (RDS). This condition, common in premature infants due to immature lungs, makes breathing difficult and often requires medical support. By accelerating lung maturation, betamethasone helps babies breathe more easily after birth.
Beyond lung benefits, betamethasone also reduces the risk of other serious complications in premature infants. It decreases the likelihood of intraventricular hemorrhage (IVH), which is bleeding in the brain, and lowers the risk of necrotizing enterocolitis (NEC), a severe intestinal infection. Overall, antenatal betamethasone can decrease a premature infant’s chance of death by as much as 40 percent and may reduce the likelihood of developing long-term disabilities like cerebral palsy.
Potential Side Effects and Considerations
For the mother, betamethasone injections can lead to temporary side effects. These may include a transient increase in blood sugar levels, particularly relevant for women with pre-existing or gestational diabetes, as monitoring may be needed. Other temporary effects can include fluid retention, mild mood changes, or discomfort at the injection site.
For the baby, a temporary decrease in fetal movement might be observed. Generally, these effects are considered mild and temporary, and research suggests the benefits of a single course of antenatal corticosteroids outweigh risks. However, repeated courses may be associated with lower birth weights and reduced head circumference, which is why multiple courses are not recommended. Expectant mothers should discuss any pre-existing medical conditions or concerns with their healthcare provider before receiving the injection.