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Norepinephrine dose-conductance-response relationships were determined for the placental and nonplacental vasculatures of ewes between 95 and 130 days of gestation with the use of radioactive-labeled microspheres injected under flow meter guidance. The regression line for the placental circulation differed significantly from that for the nonplacental circulation (P less than 0.01). The decrease in nonplacental conductance was 30 to 45% of control greater than the decrease in placental conductance. These responses are consistent with the hypothesis that the site of placental vascular resistance is in vessels of larger caliber than those which are usually the primary site of resistance to blood flow.

The rates and distributions of uterine blood flow (UBF) were measured in conscious castrated ewes during estradiol, progesterone, and combined-hormone regimens. Supplemental progesterone decreased the magnitude of UBF observed on estradiol alone. Progesterone favored distribution of UBF to the uterine caruncles and estradiol favored distribution to the myometrium and uterine cervix. Proportionate endometrial blood flows were similar on all hormone regimens. These observations suggest that estradiol secretion may not be responsible for the definitive increase in UBF observed during ovine pregnancy.

Intravascular procaine, lidocaine, mepivacaine, and bupivacaine decrease blood flow to the placental and nonplacental vascular beds of gravid ewes by stimulating vasoconstriction and myometrial contractility. These effects appear to be direct ones since they are not affected by alpha-adrenergic blockade. Dose-response curves determined in nonpregnant ewes indicate that significant decreases in blood flow may occur at arterial blood concentrations encountered clinically. It is proposed that reduced placental blood flow is the cause of fetal bradycardia following paracervical block anesthesia. The implications of these findings in obstetric anesthesia are discussed.

A study of the capability of the roll-over test to predict pregnancy-induced hypertension was undertaken using our private patients. Sixty primigravid and 60 multigravid patients were studied between the twenty-eighth and thirty-second week of gestations. These patients were chosen at random by one of our two nurses who conducted all these studies. All results were recorded but were not available to the physicians. Eighteen months later, after all study patients had delivered, the hospital charts and the patients' office records were evaluated to determine if preganancy-induced hypertension had occurred. In primigravid patients a positive test accurately predicted the later development of pregnancy-induced hypertension only 50 per cent of the time while a negative test accurately predicted that it would not develop 93 per cent of the time. In multigravid patients, only 25 per cent of the patients who had positive tests later developed hypertension. The negative test in multigravid patients was accurate 94 per cent of the time.

Placental and myoendometrial pressure-flow relationships were determined in 17 gravid ewes between 29 and 110 gestational days with the use of radioactive-labeled microsphere injections under flow meter guidance. Myoendometrial relationships were consistently curvilinear with convexity toward the flow axis. From 29 to 40 days, caruncular-cotyledonary relationships were similar to myoendometrial ones. After 50 days, the relationship was slightly but significantly curvilinear with convexity toward the pressure axis. From 42 to 50 days, responses were intermediate. The changes in caruncle-cotyledon vascular reactivity correlated with the onset and maturation of interdigitation of fetal and maternal tissues during definitive placentation. A hypothesis for these changes in vascular reactivity is presented.

The significance of midline wavering in the central nervous system as a diagnostic sign in hydrocephalus was evaluated prospectively in 27 hydrocephalic fetuses. No normal fetuses in a control group exhibited a wavering midline at three different times in pregnancy. Wavering along the entire length of the midline was seen in all 27 affected infants with hydrocephalus diagnosed from 12 to 42 weeks' gestation, prior to determination of an abnormal lateral ventricular width:hemispheric width ratio in one of 23 cases for which data were available and prior to an increased biparietal diameter in 25 (48%). One fetus, not included in the series, showed wavering of the midline echo and had an abnormal lateral ventricular width:hemispheric width ratio. The neonate was later shown to have trisomy 21 (47,XY,+21) and is suspected to have had a transient ventriculomegaly. Wavering along the complete length of the midline echo appears to be a constant finding in hydrocephalus in the fetus.