Intraamniotic Triidothyronine instillation for prevention of respiratory distress syndrome in pregnancies complicated by hypertension

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Abstract
Intraamniotic thyroxine administration is beneficial in cases of pregnancy hypertension for fetal pulmonary maturity enhancement. Triiodothyronine (T3) similar to thyroxine (T4) except for its increased potency per mole was administered intraamniotically to 15 hypertensive patients with preterm deliveries. The hypertensive disorder was severe preeclamptic toxemia (7 cases); superimposed preeclampsia upon chronic hypertension (6 patients) and underlying diabetes mellitus (2 patients). Premature labor was elective in 8 and spontaneous in 7 cases. The mean gestational age was 32.4 wk. The administration-delivery interval following 40 mg intraamniotic T3 ranged from 6 to 72 h. Eight untreated spontaneous preterm deliveries (gestational age 33.6 wk) served as a control group. Blood samples were collected from the umbilical cord and from the newborn at intervals of 24, 48 and 72 h following delivery. T3 and TSH levels were investigated by radioimmunoassay methods. Cord blood T3 levels were similar in the treated (70.2 .+-. 10.4 ng/dl) and the control groups (71.2 .+-. 9.7 ng/dl). There were no significant differences in T3 concentration between the 2 groups 24, 48 and 72 h after delivery. TSH values of cord blood in the study group ranged from 2.0 to 8.2 .mu.U/ml (mean 4.6 .mu.U/ml) and in the control group from 3.0 to 11.2 .mu.U/ml (mean 5.1 .mu.U/ml). These differences are not statistically significant. In the 7 cases where amniotic fluid T3 were fluid determined at delivery, levels were excessively high (275-600 ng/dl). Low Apgar scores were noted in 10 of the 15 neonates. Respiratory distress syndrome occurred in 7 cases (43.8%) with 3 deaths. The present study of 25 very high-risk, hypertensive patients with preterm deliveries does not seem to reveal any positive effect of 40 .mu.g intraamniotic T3 administration upon the incidence and severity of respiratory distress syndrome. Fetal blood analysis of T3 and TSH levels following delivery showed no evidence of T3 reaching the fetal compartment in these highly stressed pregnancies.