Antenatal interventions based upon fetal surveillance of the daily opioid-exposed fetus: a descriptive analysis

Objective: Daily opioid dependence for maternal pain management, methadone maintenance, or buprenorphine/naloxone therapy is an increasing trend in modern obstetrics. Opioids may produce depressive effects on fetal neurobehavioral status and thus on fetal heart rate patterns. Our primary objective was to describe the current methods utilized in antenatal monitoring of the daily opioid exposed fetus; and to describe interventions based upon monitoring which precipitated a recommendation for delivery. Our ultimate goal was to determine an optimal, evidence-based recommendation for fetal assessment of the daily opioid exposed pregnancy.Study design: A retrospective review of patients undergoing antenatal assessment from January 2016 through April 2017 at two maternal-fetal medicine testing centers identified singleton, fetuses without a known major genetic abnormality with daily opioid exposure. Nonstress tests, amniotic fluid indexes, biophysical profiles, umbilical artery Doppler measurements, and serial biometry were analyzed. Test characteristics and frequency of interventions for abnormal monitoring were quantified.Results: Criteria for daily opioid exposure was identified in 27 patients (77.8% on methadone (n = 21), 14.8% on prescription opioid for chronic pain (n = 4), and 7.4% on buprenorphine/naloxone (n = 2)). Mean maternal age was 30.3 years ±5.5 (range 21-42 years). Parity zero was 6/27 (22.2%). Identified race was 52% Caucasian, 26% African American, 19% Hispanic, and 4% Pacific Islander. There were 112 growth scans, 102 biophysical profiles, 10 isolated nonstress tests, and 81 umbilical artery Doppler studies reviewed. Delivery precipitated by abnormal testing occurred in 6/27 patients (22.2%). Gestational ages of delivery were all between 36 and 38 weeks. Indications for delivery were isolated oligohydramnios 2/6 (one at 37 weeks, one at 38 weeks), oligohydramnios with associated intrauterine growth restriction 2/6 (both at 36 weeks), isolated nonreactive nonstress test 1/6 (occurring at 38 weeks), and low biophysical profile score 1/6 (occurring at 36 weeks). The average nonstress test baseline was 131 (±11) beats per minute (range of 120-150), with no episodes of significant fetal bradycardia or tachycardia. Overall, 94.6% (106/112) of the nonstress tests were reactive, all nonstress tests had variability, 96.4% (108/112) had moderate variability, and 99.1% (111/112) had no decelerations. Time to nonstress test reactivity was <20 min in 93% (104/112), with a mean time to first acceleration of 5.3 (±7.7) min (range of 1-44). Umbilical artery Doppler measurements had an elevated systolic to diastolic ratio >95% for gestational age in 9/83 cases, with no measurements demonstrating absent or reversed end diastolic flow. Umbilical artery Doppler studies did not initiate changes in management.Conclusion: In our population, antepartum assessment with a biophysical profile at no later than 36-week gestation identified all fetuses with testing abnormalities necessitating delivery in the daily opioid exposed fetus (6/27, 22.2%). Oligohydramnios was the most frequent indication for delivery. Serial growth ultrasounds by 32 weeks were necessary to identify the 11.1% of growth restricted, opioid exposed fetuses. A depressive effect of daily opioids on nonstress test reactivity or variability was not evident in our cohort. Future studies should attempt to define optimal monitoring based upon category of opioid dependence, type and dose of opioid consumed, and timing of opioid administration.