SAN FRANCISCO (FRONTLINE MEDICAL NEWS) – Infants born to mothers receiving methadone maintenance treatment show poorer-than-average neurodevelopment outcomes, a retrospective study found.

Delays or difficulties in motor abilities appeared first in these children, followed by evidence of cognitive problems in their second year of life, reported Cristina Borradori Tolsa, MD, of University Hospital, Geneva.

“Higher methadone doses during pregnancy can have a detrimental effect on neonatal characteristics and children’s psychomotor development,” Dr. Borradori Tolsa said at the Pediatric Academic Societies meeting. She noted the need for long-term follow-up of children prenatally exposed to methadone maintenance therapy to evaluate their cognitive abilities and school readiness at preschool ages.

The researchers retrospectively analyzed records of children born to 61 mothers who were receiving methadone maintenance therapy and who gave birth at Geneva Maternity Hospital. The average methadone dosage the mothers were receiving at delivery was 78.1 mg/day, with a range from 10 mg to 300 mg daily. About half the women (51%) were taking 65 mg/day or more, classified in this study as a high dose.

Only 38% of the women had exclusively used methadone, while the other 62% had used a variety of substances, including cocaine, alcohol, benzodiazepine, marijuana, and antidepressants. The women had a low average socioeconomic status based on their level of education and the occupations of the children’s fathers.

The researchers drew children’s development data from their scores on the Bayley Scales of Infant Development, Second Edition (BSID-II), at 6 months and 18-24 months. The BSID-II has an average score of 100 and includes a mental development index for language and cognitive development, and a psychomotor development index to assess fine and gross motor skills.

At age 6 months, 75% of the 40 children assessed showed some level of motor skills delay, and 33% had a moderate to severe delay in psychomotor skills. A quarter had no delay at all (a score of at least 85). The average psychomotor score at 6 months was 76, and the average cognitive score was 88. Most of the children (60%) did, however, show mental development within the normal range at 6 months.

By the age of 18-24 months, half of the 36 children assessed showed no motor delays, and half showed no cognitive delays. One in five (20%) showed a moderate to severe psychomotor delay, and 14% showed a moderate to severe mental development delay. Mild delays in mental development occurred in 36% of the toddlers assessed, and 30% showed mild delays in psychomotor skills.

A dose-response effect was seen with mothers’ higher doses of methadone at birth and their children’s psychomotor scores at 6 months. No similar association existed for mental development, and the psychomotor association disappeared by 18-24 months. At this older age, however, 68% of children born to mothers taking a high dose of methadone showed cognitive delays, compared with 29% of children born to mothers on a low dose.

Although no differences were seen in newborns’ average gestational age (an average of 37.8 weeks overall) or birth weight between the high-dose and low-dose methadone groups, infants born to mothers with high doses were more likely to be small for gestational age (P = .01) and to need longer treatment duration for neonatal abstinence syndrome (NAS) (P = .03). Overall, 44% of the newborns were small for gestational age, 28% were born microcephalic, and all but three required pharmacologic treatment for NAS. NAS treatment lasted an average 54 days for the cohort, and the average hospital stay for the babies was 76 days.

The researchers did not report having any external funding or relevant financial disclosures.


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