Maternal intravenous MgSO₄ administration and its effects on neonatal respiratory function and risk of development of hemodynamically significant patent ductus arteriosus shunts during the initial 72 hours of life

Tocolytic therapy with MgSO₄ is well-tolerated with a low incidence of significant maternal side effects. There is evidence, however, that Mg⁺⁺ accumulates in amniotic fluid with prolonged tocolysis, defined as > 72 hrs. Fetal swallowing of AF may account for the persistently higher levels seen. Objectives of this project were to track serum Mg⁺⁺ levels among mothers admitted to the L&D Suite of the Johnson City Medical Center Hospital who required IV MgSO₄ therapy > or < 72 hrs for control of pre-eclampsia or premature labor and who deliver their neonates while receiving such therapy. Neonatal Mg⁺⁺ and Ca++ levels were obtained and infants followed for development of clinical signs and echocardiographic evidence of hsPDA with left to right shunts during the initial 72° life. Data collected between 11/95 to 9/98. Infants were divided into 3 groups: controls; IV MgSO₄ exposure < 72° prior to delivery; and IV MgSO₄ exposure > 72° prior to delivery. 36/102 (36%) control infants, 42/159 (26%) < 72° exposed infants and 20/36 (56%) infants > 72° exposure prior to delivery. parameter controls IV MgSO₄ < 72° IV MgSO₄ > 72°# 36 42 20 Birthweight 1296.2 (464-3330) 1024.0 (456-3219) 1021.6 (527-1715) Gestational Age 28.4 (23-36) 28.2 (22-33) 27.9 (24-33) Patients with hspdas (11/95-9/98) Results to date indicate higher average Mg⁺⁺_B among infants exposed to maternal MgSO₄ > 72° than among those infants exposed < 72° or controls. Incidence of hsPDAs requiring indocin IV therapy > 2:1 (> 72° group vs < 72° group) without significant differences among BW or GA suggesting a ductal musculature relaxing effect resulting in a higher incidence of hsPDAs requiring indocin therapy.