EVect of antenatal administration of thyrotrophin releasing hormone on fetal flow velocity waveforms

Aim—To determine whether antenatal administration of thyrotrophin releasing hormone (TRH), to promote lungmaturation, alters blood flow through the fetal middle cerebral, umbilical artery, or ductus arteriosus and through the maternal uterine arteries. Methods—The eVect of transplacentally administered TRH on the fetal circulation was prospectively evaluated in 30 patients between 24 and 34 weeks’ gestation. TRH (400 μg) was given to the mother intravenously either as a bolus or an infusion. Fetal eVects were determined by measuring the maximum velocity and pulsatility index (PI) in middle cerebral artery, ductus arteriosus, uterine artery and umbilical artery Doppler waveforms. Measurements weremade immediately before, and 10 and 60 minutes after maternal TRH administration. Results—Intravenous injection of TRH had no significant eVect on PI in the uterine, umbilical, or middle cerebral artery and the ductus arteriosus within 60 minutes of administration in either group. Conclusion—The antenatal use of TRH in conjunction with steroids for fetal lung maturity does not aVect utero-placental or fetal haemodynamic variables, as measured by Doppler. These findings, therefore, do not support the suggestion that antenatal intravenous administration of TRH either as bolus or infusion may have immediate adverse vascular eVects in the fetus. (Arch Dis Child 1997;77:F127–F130)