Is Dexamethasone Safe in Pregnancy?

Dexamethasone is considered safe enough for its primary obstetric use that it remains a cornerstone of care worldwide, but “safe” here carries meaningful caveats depending on the timing, dose, number of courses, and reason it is being given. When prescribed as a single course to accelerate fetal lung maturation before an expected preterm delivery, the drug’s benefits for the baby consistently outweigh its risks. Outside that well-studied scenario, the picture gets murkier, and some uses remain genuinely controversial.

Why Dexamethasone Is Given During Pregnancy

The most common reason a pregnant person receives dexamethasone is to help a baby’s lungs mature faster when preterm delivery looks likely. Babies born too early often lack enough surfactant, the slippery substance that keeps tiny air sacs in the lungs from collapsing with each breath. Dexamethasone crosses the placenta and binds to receptors inside fetal lung cells, triggering them to ramp up production of surfactant and to mature structurally sooner than they otherwise would.¹ The steroid also reduces the permeability of tiny blood vessels in the lungs and speeds up the maturation of surfactant-associated proteins.² The standard regimen is four intramuscular injections of 6 mg given twelve hours apart, completed over about two days.

How Much It Helps the Baby

The clearest benefit is a sharp drop in respiratory distress syndrome. In one well-cited trial of pregnancies complicated by premature rupture of membranes, the rate of respiratory distress fell from about half of untreated babies to a quarter of those whose mothers received dexamethasone. The treated group also had fewer cases of bleeding inside the brain, shorter hospital stays, and lower costs.³

The survival advantage extends to low-resource settings, where neonatal intensive care is less available and the stakes of preterm birth are higher. A large trial across hospitals in low-resource countries found that neonatal death dropped from roughly 24% in the placebo group to about 20% in the dexamethasone group, and combined stillbirth-plus-neonatal-death rates also fell, with no significant increase in maternal infections.⁴ A separate nested case-control study found mortality rates more than three times higher among neonates whose mothers did not receive the drug compared to those who did.⁵

Effects on Fetal Growth

A trade-off that does show up consistently is a small reduction in the baby’s size at birth. A large observational analysis found that antenatal corticosteroid exposure was associated with about a 63-gram decrease in birth weight and a roughly 3-millimeter decrease in head circumference. Even after accounting for the lower body weight, head circumference was still disproportionately smaller, suggesting the brain may be slightly more sensitive to the drug’s growth-slowing effects than the body overall.⁶

A systematic review of the broader literature found reductions in birth weight across roughly half of the studies that examined it, with the size of the reduction ranging widely. About half the studies looking at head circumference also reported a decrease.⁷ However, a French multicenter study that followed full-term newborns who had been exposed to antenatal corticosteroids found no higher risk of having a head circumference below the fifth percentile. Birth length was more likely to be below the fifth percentile in exposed babies, but the head circumference finding was reassuring.⁸

The inconsistency across studies matters. The babies in these analyses are preterm or at risk of preterm birth, which itself affects growth. Disentangling the drug’s effect from the underlying condition that prompted treatment is hard, and the studies that do it most carefully tend to find smaller effects. For a single course given at the right time, the growth reductions are modest and widely considered acceptable given the survival benefit.

Temporary Changes in Fetal Behavior

In the two days after administration, the baby’s movements and heart rate patterns change noticeably on monitoring. A trial comparing dexamethasone and betamethasone found that both drugs substantially suppressed fetal heart rate accelerations, movement, and breathing activity at the 48-hour mark. All of these parameters returned to baseline by 96 hours.⁹ This is worth knowing because a fetal monitoring session performed shortly after treatment can look alarming if nobody realizes the drug is the explanation. The suppression is temporary and does not indicate harm.

What It Does to Maternal Blood Sugar

Dexamethasone temporarily raises blood glucose levels in the mother. In a study tracking glucose and insulin before and after treatment, blood sugar was significantly elevated at 24 and 48 hours after treatment began, then returned to pre-treatment levels by 72 hours.¹⁰ For women with gestational diabetes, this spike requires closer monitoring. A randomized trial compared two dosing schedules in women with mild gestational diabetes and found that a two-dose regimen of 12 mg rather than a four-dose regimen of 6 mg produced fewer hyperglycemic episodes on the second day, suggesting the condensed regimen may be easier to manage for this population.¹¹ In either case, the glucose disruption is short-lived and manageable with monitoring.

Dexamethasone Versus Betamethasone

Betamethasone is the other corticosteroid used for fetal lung maturation, and a reasonable question is whether one is safer than the other. A systematic review and network meta-analysis found no meaningful difference between the two drugs for most outcomes that matter: neonatal death, neurodevelopmental disability, bleeding in the brain, or birth weight were all statistically and clinically similar.¹² A large randomized trial also confirmed similar rates of death or neurosensory disability between the two drugs, with about a third of infants in each group affected. Dexamethasone caused less discomfort at the injection site, which was the most common side effect reported by the mothers.¹³

Where the picture gets less equal is with repeated courses. A study following infants to age two found that multiple courses of dexamethasone, but not betamethasone, were associated with a higher risk of white-matter injury (leukomalacia) and neurodevelopmental problems.¹⁴ This finding has pushed many clinicians toward betamethasone when repeat dosing is being considered, though both drugs carry greater risk with repeated exposure.

The Problem With Repeat Courses

A single course of dexamethasone has a fairly clean safety record. Repeat courses are where the evidence turns cautionary. In a primate study, repeated courses of antenatal corticosteroids reduced the density of myelinating cells in the brain compared to both single-course and control animals.¹⁵ Myelin is the insulation around nerve fibers that allows fast, efficient signaling, so fewer myelinating cells is not a trivial finding.

Human data point in the same direction. A study assessing infants at one year found that those exposed to antenatal dexamethasone were about 1.6 times more likely to score below competence thresholds in cognitive development compared to unexposed infants.¹⁶ Current guidelines generally recommend a single course, with a possible single “rescue” course if preterm delivery remains imminent more than a week after the first. Routinely stacking courses is not supported by the evidence.

Longer-Term Worries From Animal and Human Studies

Animal research raises concerns that go beyond the neonatal period. In a primate study, offspring exposed to dexamethasone in utero showed impaired glucose tolerance, higher insulin levels, elevated blood pressure, and an exaggerated stress-hormone response by eight to twelve months of age. Their pancreatic insulin-producing cells were reduced by about a quarter.¹⁷ Rat studies have similarly found that dexamethasone-exposed pups catch up in weight by weaning but develop permanent hypertension and metabolic abnormalities as adults.¹⁸ A recent study has also identified an epigenetic mechanism behind lasting vascular changes: dexamethasone exposure altered methylation patterns in a gene involved in blood-vessel relaxation, reducing the ability of blood vessels to dilate properly in male offspring.¹⁹

Human long-term data are harder to come by, but one study of school-age children whose mothers received dexamethasone in early pregnancy (for congenital adrenal hyperplasia, not lung maturation) found higher rates of overweight and lower intelligence scores in the treated group. The earlier in pregnancy the treatment started, the more pronounced the effect on IQ appeared.²⁰ A separate assessment of children exposed to dexamethasone during the first trimester for the same condition found normal full-scale IQ but impaired verbal working memory and increased social anxiety.²¹

These findings do not translate directly to the standard lung-maturation regimen, which involves a brief course much later in pregnancy. The first-trimester exposures studied in the congenital adrenal hyperplasia literature are longer, start earlier, and hit a period when the fetal brain is especially vulnerable. Still, they serve as a reminder that glucocorticoid exposure during development is not biologically inert, and they are part of why clinicians try to limit the dose and number of courses to the minimum that is beneficial.

First-Trimester Use for Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) is a genetic condition where the fetus produces excess androgens, which can cause ambiguous genitalia in affected girls. Some centers give dexamethasone starting in the first trimester to suppress these androgens before sex differentiation occurs. This is a completely different use from third-trimester lung maturation, and it is far more controversial.

A systematic review of the available evidence concluded that dexamethasone does appear to reduce virilization in affected female fetuses without clearly causing serious maternal or fetal harm in the short term. But the review also stressed that all the evidence is observational, sample sizes are tiny, and meaningful conclusions about safety are difficult to draw.²² A more recent review echoed this uncertainty, noting that no randomized trials exist and practice varies widely across centers in terms of which glucocorticoid is chosen and how risks and benefits are weighed.²³

What makes this use especially tricky is that treatment must begin before the fetus’s sex or genetic status is known. That means roughly seven out of eight treated pregnancies are exposed unnecessarily, because only one in four fetuses will be female, and only one in four of those will carry the classical form of the disease. The neurodevelopmental findings described earlier come mainly from this group, where exposure is weeks or months long and starts during the most sensitive period of brain development. For families considering this option, the decision is genuinely personal and requires weighing uncertain long-term risks against the known burden of genital virilization.

Does It Help in Late Preterm Births?

A question that has received more attention recently is whether dexamethasone benefits babies expected to be born in the late preterm window, roughly 34 to 36 weeks. The evidence here is thin. A multicenter, double-blind, placebo-controlled trial in low-resource countries found that dexamethasone given in late preterm pregnancies did not reduce neonatal death, combined stillbirth and neonatal death, or severe respiratory distress. There was some reduction in a secondary measure of milder respiratory problems, and no evidence of harm to mothers or babies.²⁴ The investigators noted that potential benefit could not be ruled out and called for more trials.

A trial is currently underway to examine whether lower doses of dexamethasone (4 or 5 mg instead of the standard 6 mg) work as well across a wide gestational range, from very preterm through late preterm. This trial aims to fill a gap, since the standard 6-mg dose was established decades ago without the kind of dose-finding work that modern drug development expects.²⁵ Until those results arrive, the case for late preterm use remains unproven.

Why Formulation Can Matter

An often-overlooked detail is what else is in the vial besides dexamethasone itself. An experimental study tested whether dexamethasone or betamethasone harmed developing brain cells in culture. Pure versions of both drugs did not increase neuronal death and actually protected neurons against certain types of injury. But a commercial dexamethasone formulation that contained sulfite preservatives significantly increased neuronal loss and blocked the protective effect entirely.²⁶ This suggests that some of the neurotoxicity attributed to dexamethasone in older studies may have been driven partly by preservatives rather than the drug itself. It also means that not all dexamethasone products are interchangeable from a safety standpoint, and preservative-free formulations are preferred when available.

Translating Animal Data to Humans

Many of the scarier findings about metabolic programming and brain development come from animal models, and it is worth being honest about their limits. A review specifically addressing this issue noted that no animal truly recapitulates human pregnancy and that results from animal studies need rigorous pharmacokinetic scaling before being extrapolated to humans.²⁷ Rodent and primate studies often use doses or durations that exceed what a human fetus would receive from a standard lung-maturation course. That does not mean the animal findings should be dismissed, but they are best understood as signals about what could go wrong rather than demonstrations of what does go wrong in typical clinical use. The fact that human follow-up studies of standard single-course regimens generally show reassuring outcomes fits with the idea that the doses used clinically sit below the threshold for the worst effects seen in animal experiments.

When Dexamethasone Is Used for Maternal Illness

During the COVID-19 pandemic, dexamethasone gained attention as a treatment for severely ill adults regardless of pregnancy status, after a major trial showed it reduced mortality by up to a third in mechanically ventilated patients and by about a fifth in those receiving supplemental oxygen. For pregnant patients specifically, however, guidelines from the Royal College of Obstetricians and Gynaecologists recommended oral prednisolone or intravenous hydrocortisone rather than dexamethasone for treating maternal COVID-19.²⁸ The reasoning is straightforward. Prednisolone and hydrocortisone are largely inactivated by a placental enzyme before reaching the fetus, so they treat the mother’s inflammation without flooding the baby with glucocorticoid. Dexamethasone bypasses that enzyme, which is exactly why it works for fetal lung maturation but makes it a less ideal choice when the goal is treating the mother alone. This distinction trips up people who hear “dexamethasone is used in pregnancy” and assume it is universally interchangeable with other steroids. The choice of corticosteroid depends entirely on whether the intended target is the mother, the fetus, or both.