Fentanyl use during pregnancy can lead to adverse outcomes in infants, including poor growth, stillbirth, preterm delivery and fetal distress during labor. Researchers now suggest the possibility of a novel syndrome in infants whose mothers used fentanyl during pregnancy.

In a study, published in the journal Genetics in Medicine Open, researchers identified similar facial and musculoskeletal abnormalities such as short stature, microcephaly (small head) and congenital anomalies in 10 infants who were exposed to fentanyl during pregnancy.

The study began in 2022, when a genetic counselor and a group of physicians at Nemours Children's Hospital, Delaware, observed similar facial features and multiple physical abnormalities in several newborns who were brought to the hospital with complaints of feeding difficulties.

Initially, six infants were enrolled in the institutional review board-approved study. Later, four more from other institutions were added.

In addition to small heads, short stature and distinctive facial features, many of them had congenital malformations that included cleft palate, talipes equinovarus or rocker bottom feet (a clubfoot anomaly) and chordee (a condition that causes a downward curve of the penis), or hypospadias (when urethral opening is on the underside of the penis rather than the tip). They also had short, broad thumbs, single palmar creases (normally people have three creases), and mild fusion of the toe digits.

Researchers initially suspected Smith-Lemli-Opitz syndrome, a rare genetic condition that causes distinctive facial features, small head size, intellectual disability and behavioral problems. However, genetic testing ruled out the possibility.

The team then tested the babies for fetal alcohol syndrome as it is also associated with similar symptoms such as distinctive facial features and a small head. Since the test ruled out the possibility and the mothers were all users of fentanyl, researchers suspect it to be a new syndrome.

Further research and lab experiments are needed to confirm if fentanyl caused the abnormalities, or if any other drug or contaminant is responsible for it.

"Given the fentanyl use epidemic, it is important to recognize this condition. Analogous to prenatal alcohol exposure causing fetal alcohol syndrome with long-term physical and developmental consequences, this novel condition may impact many infants in life-changing ways," said senior author Karen W. Gripp, chief of the division of Medical Genetics at Nemours Children's Health, Delaware Valley.

Gripp said the team has come across several anecdotes and observed clinical reports indicating that more children born to mothers who used fentanyl exhibit similar characteristics. However, they had varying degrees of symptoms and severity, suggesting the possibility that the novel syndrome may exist on a spectrum.