Celestone (betamethasone) is a corticosteroid injection given during pregnancy to speed up a baby’s lung development when preterm delivery is likely. The goal is to reduce the serious complications that premature babies face, especially difficulty breathing on their own. It is one of the most well-studied and effective interventions in obstetric care, typically given as two injections 24 hours apart.
How It Helps a Baby’s Lungs Mature
A baby’s lungs are among the last organs to fully develop. In the final weeks of pregnancy, the lungs begin producing surfactant, a slippery substance that coats the inside of the air sacs and keeps them from collapsing each time the baby exhales. Babies born too early often don’t have enough surfactant, which leads to a dangerous condition called respiratory distress syndrome (RDS).
When betamethasone crosses the placenta, it triggers the baby’s lungs to mature faster and ramp up surfactant production ahead of schedule. This gives premature babies a significantly better chance of breathing on their own after birth. The effect isn’t limited to the lungs. The steroid also helps other organ systems mature, reducing the risk of bleeding in the brain and a serious intestinal condition that affects premature newborns.
How Much It Reduces Preterm Complications
The benefits are substantial. Compared to babies whose mothers did not receive the injection, babies who were exposed to antenatal corticosteroids have roughly a 34% lower risk of respiratory distress syndrome, a 46% lower risk of brain hemorrhage, and a 54% lower risk of the dangerous bowel condition called necrotizing enterocolitis. The risk of death from prematurity drops by about 31%. These numbers come from large pooled analyses and represent one of the clearest success stories in prenatal medicine.
When It’s Given
The standard window for Celestone is between 24 and 34 weeks of pregnancy, when there is a reasonable expectation that delivery could happen within the next seven days. This could be because of preterm labor, premature rupture of membranes, a medical condition requiring early delivery, or other complications that make it unlikely the pregnancy will continue to full term.
The treatment can also be given in the late preterm period, between 34 and 36 weeks, for women who haven’t received a prior course and are expected to deliver within seven days. However, an indicated delivery in this window should never be delayed just to complete the steroid course. The benefits are greatest when delivery occurs between 24 hours and 7 days after the first injection, which is why timing matters so much.
In some cases, a single “rescue” course may be considered if a woman received her initial course more than two weeks earlier and preterm delivery again appears imminent. Repeated full courses are generally avoided because the added benefit diminishes while potential risks increase.
What the Injection Feels Like
Celestone is given as an intramuscular injection, usually in the hip or upper arm. You receive two doses: 12 milligrams each, spaced 24 hours apart. The injection itself can sting or cause soreness at the site, but the process is quick. Most women receive the shots during a hospital admission or observation stay, since the circumstances prompting the treatment (preterm labor, complications) typically require monitoring anyway.
Effects on Your Blood Sugar
The most notable maternal side effect is a temporary spike in blood sugar. This happens to most women who receive the injection, not just those with diabetes. Research tracking blood glucose after betamethasone found that about 84% of high blood sugar episodes occurred within the first 48 hours. Blood glucose levels typically return to normal by 72 hours after the first injection.
For women with gestational diabetes or pre-existing diabetes, the blood sugar disruption can be more significant. Pregnancy already increases insulin resistance, and adding a high-dose steroid on top of that can cause sharp glucose swings. If you have diabetes, expect closer monitoring for at least 72 hours: frequent blood sugar checks, possible insulin adjustments, and potentially a short hospital stay in a monitored setting. The effect is temporary, but it needs active management during that window.
Other short-term side effects are relatively minor. Some women notice a brief increase in energy or restlessness, mild swelling, or a temporary increase in white blood cell count on lab work (which can be confusing if doctors are also watching for signs of infection). These resolve on their own.
Long-Term Safety for Children
One of the most reassuring findings about Celestone in pregnancy comes from long-term follow-up studies. A major follow-up of nearly 950 children whose mothers were randomized to receive either betamethasone or a placebo found no differences in cognitive ability, motor function, social behavior, or behavioral problems at a median age of 7 years. About 17% of children in the steroid group and 18.5% of children in the placebo group scored below average on standardized intelligence testing, a difference that was not statistically meaningful. The original trial had shown a small increase in newborn low blood sugar episodes, but this did not translate into any detectable developmental consequences years later.
Why Timing Matters More Than the Drug Itself
The effectiveness of Celestone depends heavily on when it’s given relative to delivery. The steroid needs roughly 24 hours to begin its work, and the peak benefit occurs within the first seven days after the course. If delivery happens within just a few hours of the first injection, the baby gets only partial benefit. If delivery doesn’t happen for weeks, the effect wanes. This is why your medical team will weigh the likelihood and timing of delivery carefully before recommending it, and why a rescue course may come into play if the initial course was given far in advance.
For pregnancies that remain stable after the steroid course, the fact that the window of maximum benefit has passed doesn’t mean the treatment was wasted. Even partial benefit offers some protection, and the lungs continue to mature naturally with each additional day of pregnancy.