Steroid medications given before preterm birth improve lung and placental function, research shows

A new rat study explores lung function and placental changes in the presence of infection and inflammation. The study suggests treating the mother with steroids before giving birth may improve both lung and placental function, potentially preventing a common lung disorder associated with prematurity.

The findings of this first-of-its-kind study are published in the American Journal of Physiology-Lung Cellular and Molecular Physiology.

Ten percent of babies worldwide are born prematurely. One of the most common conditions preemies experience is impaired lung development, which often leads to a condition called bronchopulmonary dysplasia (BPD).

BPD causes breathing difficulties and the need for supplemental oxygen, which also carries health risks. BPD can be caused by a variety of factors, including a type of inflammatory infection in the mother’s uterus called chorioamnionitis. The more severe the mother’s infection, the more severe BPD tends to be.

A standard of care for pregnant mothers is to administer steroids before the baby is born to help improve infant lung function. But the impact of these steroid treatments on the placenta has not been well-defined.

Abnormal function of the placenta in a pregnancy affected by chorioamnionitis may also negatively affect prenatal lung development, but the exact mechanisms aren’t understood. In this new study, researchers analyzed the effects of prenatal steroid treatments on the placenta tissue as well as infant rats’ lung tissue and pulmonary function two weeks after birth.

A group of pregnant rats were treated with the steroid betamethasone two days before giving birth. The research team examined placental structure at birth and lung function in the infants when they were two weeks old. Compared to animals that were not treated for infection and a control group without the associated inflammation, the treated group:

• Showed restored lung structure.
• Increased pulmonary vessel density.
• Normalized spiral artery formation in the placenta. Spiral arteries deliver blood (and nutrients) from mother to child.
• Showed alteration of multiple placental genes, including decreased inflammatory signaling and an increase in placental prolactin, a hormone involved in maintaining healthy pregnancies. Prolactin is a particularly interesting target for future studies because its role in lung development or lung injury has not yet been characterized.

“These findings suggested that antenatal steroids improve placental function, preserve lung growth, and prevent [right ventricular hypertrophy] in infant rats, suggesting a potential benefit for the prevention of BPD,” the researchers wrote.