Acoustic cry characteristics of infants exposed to methadone during pregnancy

Objective: Infant cry characteristics reflect the neurological and medical status of the infant. This study compared the acoustic cry characteristics of infants born to mothers maintained on methadone during pregnancy with those of infants not exposed to methadone during pregnancy. Methods: At 42 weeks of post-menstrual age, 89 crying episodes ranging in duration from 1.15 to 1.97 sec were collected from 10 methadone-exposed (ME) and 10 non-methadone-exposed (NE) infants. Cry utterances were analysed acoustically using spectrographic displays and measures of cry utterance duration and fine-grained analyses of the fundamental frequency calculated for each cry. Results: No between-group differences were found on measures of cry duration or fundamental frequency. However, analyses of frequency perturbation showed that the cry utterances of ME infants were characterized by significantly higher levels of frequency perturbation than the cries of infants not exposed to methadone. These effects largely persisted after statistical control for the confounding effects of other maternal drug use during pregnancy. Conclusion: The crying behaviour of infants exposed prenatally to the synthetic opiate, methadone, is characterized by higher levels of vocal fold vibratory perturbation than NE infants. These findings suggest the possibility of early, subtle neurological vulnerability in this high-risk group of infants.