Neonatal bilirubin production after preterm labor tocolysis with nifedipine

We studied the in vivo total bilirubin production, as indexed by the carboxyhemoglobin level (HbCO), of infants whose mothers had ritodrine (RIT) tocolysis or underwent tocolysis with the calcium channel blocker, nifedipine (NIF). No difference in HbCO between the infant groups was detected: NIF 0.67 +/- 0.31% saturation and RIT 0.88 +/- 0.47% saturation. We conclude that NIF is unlikely to cause a clinically important increase in total bilirubin production when used at doses sufficient for tocolysis.