Introduction: Intrapartum opioids in labor may interfere with the early breastfeeding phase and cause breastfeeding difficulties. This study examines the effects of intrapartum fentanyl given intravenously (IV) or through epidural analgesia (EDA) on early breastfeeding.

Material and methods: This is a prospective observational study conducted in a regional maternity unit. We included 1101 healthy mothers of term singleton babies in vertex presentation born between 2016 and 2018 (468 nulliparous and 633 multiparous). The main data were collected prospectively, and additional data were retrieved from hospital records. The main outcome measures were exclusive breastfeeding at discharge, spontaneous suckling, and breastfeeding problems after birth. We assessed the outcomes in four groups categorized by intrapartum opioid exposure: none, IV fentanyl, EDA fentanyl and IV+EDA fentanyl. We also analyzed the dose-response relation of fentanyl administered by epidural or IV and early breastfeeding. Ultimately, we dichotomized the IV fentanyl group into two groups (≤200 µg and >200 µg) to further study the effect on early breastfeeding.

Results: The odds of non-exclusive breastfeeding were doubled with EDA fentanyl (odds ratio [OR] 2.45, 95% CI 1.34-4.48, p = 0.004) and four times higher with IV+EDA fentanyl (OR 4.20, 95% CI 2.49-7.09, p < 0.001) compared with no opioid exposure. Spontaneous suckling was negatively associated with intrapartum fentanyl use (p < 0.001) irrespective of mode of administration. When the IV fentanyl doses exceeded 200 µg compared with less than 200 µg, we found a reduction in exclusive breastfeeding (81% vs. 89%; p = 0.014) and spontaneous suckling (68% vs. 83%; p < 0.001) and an increase in breastfeeding problems (41% vs. 27%; p = 0.004).

Conclusions: Fentanyl in labor is associated with breastfeeding difficulties. However, IV fentanyl in low doses (≤200 µg) seems to affect breastfeeding less than EDA fentanyl and is therefore a viable alternative when labor analgesia is needed. This could be most relevant for multiparous women, where a shorter labor is expected. More research is needed to determine the optimal dose and route of administration of fentanyl for labor analgesia.