Hypertensive effect of antenatal thyrotropin-releasing hormone in pre-eclampsia

Effect 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 lung maturation, alters blood flow through the fetal middle cerebral, umbilical artery, or ductus arteriosus and through the maternal uterine arteries.

METHODS

The effect of transplacentally administered TRH on the fetal circulation was prospectively evaluated in 30 patients between 24 and 34 weeks' gestation. TRH (400 micrograms) was given to the mother intravenously either as a bolus or an infusion. Fetal effects 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 were made immediately before, and 10 and 60 minutes after maternal TRH administration.

RESULTS

Intravenous injection of TRH had no significant effect 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 affect 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 effects in the fetus.

Effect of antenatal thyrotropin-releasing hormone on uterine contractility, blood pressure, and maternal heart rate

OBJECTIVE

The goal was to study the effects on uterine contractility, blood pressure, and heart rate of thyrotropin-releasing hormone given antenatally in combination with glucocorticoids to accelerate fetal maturation.

STUDY DESIGN

A placebo-controlled, randomized, double-blind study was performed involving 30 women whose pregnancies were followed up at the University Hospital Gasthuisberg in 1994 and 1995.

RESULTS

Thyrotropin-releasing hormone induced a significant mean increase of nearly 6 mm Hg in systolic blood pressure and approximately 5 mm Hg in diastolic blood pressure. The duration of this raise was < 20 minutes. Thyrotropin-releasing hormone had no significant effect on maternal heart rate or uterine contractility: 4.2 +/- 1.6 contractions per hour before versus 4.7 +/- 1.7 contractions per hour after treatment.

CONCLUSIONS

Thyrotropin-releasing hormone induces a small (mean < 6 mm Hg) and brief mean (< 20 minutes) increase in blood pressure but appears to have no clinically detectable effect on uterine contractility.

Antenatal lung maturation--should we all be using thyrotropin-releasing hormone?

Thyrotropin-releasing hormone (TRH) appears to be a promising antenatal therapy to help reduce neonatal lung disease. Clinical trials, however, show differing results. At present the optimum dosage, frequency and method of administration have not been established. TRH has been shown significantly to elevate blood pressure in patients with preeclampsia suggesting it should not be used in this group. Moreover concerns over its use in growth retarded fetuses and its long-term neonatal effects have not been addressed. Further trials are needed before routine clinical use can be recommended.