Effects of maternal magnesium sulfate administration on intestinal blood flow velocity in preterm neonates

Background: Antenatal MgSO ₄ administration is used extensively as a tocolytic agent and to treat preeclampsia. Various effects on the fetus and newborn have been reported, and MgSO ₄ has well-documented vasoactive effects. Objective: To determine if antenatal MgSO ₄ administration affects intestinal blood flow velocity in newborn preterm infants. Methods: Peak, mean and end-diastolic velocities in the superior mesenteric artery were measured on day 1 of life. Maternal medical records were reviewed to identify infants whose mothers had been administered MgSO ₄ for preterm labor or preeclampsia within 24 h of delivery. Result: Fifty-six infants were studied: 27 were exposed and 29 were not exposed to antenatal MgSO ₄. Mean birth weight (1,371 ± 349 and 1,401 ± 469 g, respectively), gestational age (29.7 ± 2.0 and 30.0 ± 2.9 weeks, respectively) and infant hemodynamic and clinical variables (other than clinical indication for antenatal MgSO ₄ administration) were similar between groups. There were no significant differences between the exposed and unexposed groups in intestinal blood flow velocities. For the exposed group, however, there was a significant negative correlation between mean velocity and the number of hours from birth to the time superior mesenteric artery blood flow velocity measurements were made (p = 0.002); there was no correlation for the unexposed group (p = 0.852). Conclusion: Group mean values indicate that antenatal exposure to MgSO ₄ does not significantly affect intestinal blood flow velocity in newborn preterm infants. However, the significant negative relationship between mean blood flow velocity and time from birth to blood flow velocity measurement in exposed infants suggests that there may be measurable effects of MgSO ₄ exposure within the hours immediately after birth. Trials that prospectively evaluate the development of intestinal blood flow velocities are needed to further clarify potential effects of antenatal MgSO ₄ on the gastrointestinal tract of preterm infants.