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A drug to suppress uterine activity with minimal or no side eflfects would be valuable for the prevention of premature or precipitous labor, or for the control of tetanic uterine contractions. Recently it has been reported that diazoxide*, a benzothiadiazine derivative, a smooth muscle relaxant [15] inhibits myometrial activity of the human uterus [3,9] with no apparent adverse reactions on the fetus [5,8]. However, the dose necessary to suppres uterine activity also causes maternal hypotension [5] and the drug has other pharmacologic actions including the induction of hyperglycemia. Because of the lack.of direct Information on the effect of the drug on the fetus, pilot experiments were conducted in our laboratory on the pregnant guinea pig and her fetus [11], Blood glucose rose to a similar degree in both mother and fetus, and when delivered, the fetuses were acidotic and severely depressed, probably äs a result of maternal hypotension. On the basis of these observations, it was feit that possible adverse effects of the drug on the fetus should be examined more carefully. This paper describes experiments on pregnant subhuman primates in which the inhibiting action of diazoxide on uterine activity, placental transfer of the drug and its effect on the cardiovascular and biochemical state of both mother and fetus were studied. Material and methodsExperiments were conducted on a total of 31 pregnant primates. These consisted of 9 rhesus monkeys (maccaca mulatta) and 7 Java monkeys (maccaca fasicularis), at gestational ages ranging from 132 to 155 days (term 168 days), and 15 baboons (papio hybrid) at gestational ages ranging from 150 to 171 days (term 185 days). Acid-base data from 42 additional pregnant primates studied earlier are included in order to evaluate changes in acid-base state of the fetus following the infusion of diazoxide. The model used has been described previously in detail [7], Briefly, catheters were placed in the fetal carotid artery or femoral artery and amniotic fluid at hysterotomy, and in the maternal femoral artery and vein. In addition, thermistor probes were placed in the fetal csophagus and maternal rectum. Post-operatively, light sedation was

Terbutaline, a resorcinol derivative of isoprenaline, is primarily an adrenergic j3 2 -receptor agonist [25]. Terbutaline has been demonstrated äs being a potent inhibitor of myometrial contractlity in vitro [1]. Recent clinical trialshave confirmed the agent's tocolytic activity in both spontaneous and oxytocin-stimulated labor [2,3,15]. the investigations showed that terbutaline was well tolerated maternally despite a moderate tachycardia. Antepartum fetal heart rate monitoring and APGAR scores did not demonstrate any unusual or adverse effects on the fetus in human [2,3,15] or animal [6,7] studies. However, presently there are no systematic clinical or other investigations showing the effect of varying matemal doses on the fetus and on uteroplacental circulation. This study was undertaken to investigate doserelated effects of terbutaline on immature fetal lambs. The drug was infused into the maternal circulation in one phase and directly into the fetal circulation in another during oxytocin-induced labor. The fetal cardiovascular and acid-bäse Status was monitored continuously. Paris V, France 1977-1978. Assistant, füll time, Faculty of Medicine ofSfax, Tunisia 1978-1979 l Materials and methodsTen pregnant ewes and their fetuses (including two sets of twins) were prepared under spinal anesthesia äs described previously [7]. Catheters were introduced into the fetal carotid artery and jugular vein and into the amniotic cavity at hysterotomy. The femoral artery and vein and main maternal uterine vein were also catheterized. An electromagnetic flow probe (Micron Instruments, Calif.) was placed around the uterine artery supplying the pregnant hörn. A minimum period of three days was allowed

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The r o l e of PGs i n t h e maintenance and t h e control of f e t a l and p l a c e n t a l hemodynamics was suggested. Umbilical vessels having smooth muscle t h a t i s not innervated may be p a r t i c u l a r l y responsive t o vasoactive agents such a s PGs. S i x UA were f r e s h l y obtained from normal term pregnancies. Biosynthesis of PGE2, PGF2c(, thromboxane A2 (analyzed a s TxB2) and prostacyclin (PG12) (Measured a s 6-keto PGFla) was studied by incubating UA microsomes with (14c) arachidonic acid (M) and with (14c) c y c l i c P G endoperoxide (PGH2), separation by t h i n l a y e r chromatograph and