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Thirty cases of fetal hydrocephalus were diagnosed at the perinatal ultrasound unit of Yale-New Haven Medical Center during a 41 month period. Prenatal ultrasound was found to be highly valuable in the detection of fetal hydrocephalus. However, the antenatal detection of associated anomalies was not as uniformly successful. The importance of a complete sonographic evaluation of intracranial and extracranial anatomy is stressed, as 10 patients with documented hydrocephalus (37%) had associated intracranial anomalies and 17 patients (63%) had associated extracranial anomalies. In this series, isolated hydrocephalus without associated anomalies occurred in only four patients (15%).

With high-resolution ultrasound equipment, it is now possible to diagnose certain fetal anomalies in the third trimester and in some cases before the twentieth week of gestation. During a 27 month period 2,548 ultrasound scans were performed in high-risk patients. An anomaly was diagnosed in 10 of 122 second-trimester patients who were at risk for recurrent fetal defects. Fetal deformity was also found in 26 third-trimester patients. Of the 2.8% of patients found to have polyhydramnios 18% were associated with various types of anomaly. With ultrasound it was possible to examine internal fetal anatomy and to identify abnormalities of the fetal cranium, spine, chest, abdomen, and limbs. These anomalies are reviewed here in detail. Based on ultrasonically derived information, second-trimester patients can be offered information concerning the status of their fetuses at risk genetically and physicians can better manage third-trimester patients with diagnosed fetal deformities.

We describe a potential screening method for the second trimester detection of the fetus with Down syndrome by the use of standard sonographic biometry. Retrospective assessment of the biparietal diameter, femur length, and biparietal diameter/femur length ratio in 55 fetuses with Down syndrome and 544 control fetuses was performed at two medical centers. Adequate numbers of cases and controls were available to permit statistically significant comparisons between the groups at 15 to 23 weeks' gestation. Fetuses with Down syndrome displayed no statistically significant differences in the cephalic index or the biparietal diameter compared with controls at a given gestational age. Significant femur length shortening was observed, but the greatest statistical difference was noted for the biparietal diameter/femur length ratio. This ratio was found to decrease with gestational age in the normal population and was consistently elevated in the Down syndrome population (compared with control) throughout the second trimester. With a cutoff value of 1.5 SD above the normal population mean for the biparietal diameter/femur length ratio, 50% to 70% of fetuses with Down syndrome could be identified in 6% of the total population (p less than 0.0001). This preliminary study suggests that the biparietal diameter/femur length ratio may prove superior to current Down syndrome screening methods and, as a third independent variable, may significantly enhance the sensitivity and specificity of combined maternal age/maternal serum alpha-fetoprotein screening modalities.

During a two-year period, nine cases of cephalocele were evaluated at the authors' perinatal ultrasound unit. There was one false positive and one false negative diagnosis. In five cases, multiple anomalies were present; three as part of the amnion rupture sequence. The obstetric management consisted of elective termination of pregnancy in five cases and cesarean section in four. The value of sonography in the diagnosis of cephalocele and associated syndromes and malformations is discussed. A plan of management and counseling based upon current understanding of prognosis is presented.

Ultrasonographic examinations were conducted between 6 and 12 weeks' gestation in 77 first-trimester pregnancies with normal fetal outcome. Each examination consisted of measurements of the secondary yolk sac diameter and the fetal crown-rump length. The yolk sac was seen in all cases, and whereas its measurements demonstrated wide biologic variability, it correlated weakly (R2 = 0.39) with gestational age as confirmed by crown-rump length measurements. Growth of the yolk sac diameter, although slight, assumed a curvilinear relationship with gestational age. Such a growth profile is best described by a second-degree polynomial regression equation. The yolk sac performs important functions for embryonic development during organogenesis and the remnant of the secondary yolk sac seen on ultrasonography is often considered to be a potential predictor of fetal outcome. Our findings indicate that the size of this remnant in pregnancies with normal karyotypes and normal fetal outcomes is extremely variable. Additionally, the yolk sac size in patients with karyotypic abnormalities and spontaneous abortion were equally variable and almost all were within the normal range. In light of these findings, the secondary yolk sac size does not appear to be a sensitive predictor of embryonic integrity and pregnancy outcome.

Previous studies have indicated that patients with elevated levels of amniotic fluid alpha-fetoprotein (AFAFP) are at very high risk for fetal neural tube defects. Twenty-eight patients whose levels of AFAFP were greater than 3 standard deviations above the mean were evaluated with a Stage II ultrasound examination for detailed assessment of fetal anatomy. In 16 patients with AFAFP levels greater than 5 SD above the mean, six fetuses with open spina bifida were identified (37.5%). Moreover, in four fetuses in this group, the diagnosis was ventral wall defects (two with gastroschisis and two with omphalocele), and one fetus had multiple lethal anomalies. The other 5 patients had normal scans, and, with the exception of one patient who was delivered of a nondysmorphic stillborn infant at 28 weeks, all had normal infants at birth. Among the other 12 patients with AFAFP levels between 3 and 5 SD above the mean, there were only two adverse findings--an intrauterine death and an omphalocele. A Stage II ultrasound examination performed when AFAFP levels are elevated enables one to distinguish between conditions which are lethal or associated with significant impairment and those which are amenable to surgical procedures. Morphologically normal fetuses can also be identified. Since this diagnostic technique will allow salvage of many pregnancies that otherwise would be aborted, it should be an integral part of any alpha-fetoprotein screening program.

During a 5-year period, a diagnosis of obstructive uropathy was made in 25 fetuses. Eight of them had unilateral obstruction and 17 were affected bilaterally. The most common condition encountered was urethral obstruction by posterior valves. The site and nature of the obstruction were correctly identified in 22 of the 25 fetuses. Among the 17 who had bilateral obstruction, only three survived. In contrast, only one infant with unilateral obstruction died (of unrelated causes). Oligohydramnios in low-level (urethral) obstruction was a uniformly lethal finding. Relief of urethral obstruction in two fetuses after 20 weeks of gestation did not result in survival of the infant, whereas shunting prior to 20 weeks in one fetus seemed to have a beneficial effect. On the basis of this experience, we suggest that unilateral obstruction would be treated best by conservative management, while in bilateral obstruction invasive treatment may be effective if initiated early in gestation, before significant oligohydramnios occurs.