Faculty Bibliography

Fetal exposure to valproic acid has recently been associated with an increased incidence of neural tube defects. The prenatal detection of a fetus with both hydrocephalus and meningomyelocele after valproic acid exposure is presented and specific recommendations made for antepartum evaluation in future pregnancies.

Sixteen isoimmunized pregnancies at risk for erythroblastosis fetalis were managed by serial amniocenteses for bilirubin delta optical density at 450 nm (delta OD450). Before amniocentesis each fetus was evaluated ultrasonically and the fetal liver size, the abdominal circumference, and the umbilical vein diameter, in both the fetal liver and the umbilical cord, were measured. The ultrasonically determined fetal liver size, as well as its growth rate, was found to be greater than normal during the last two weeks before intervention (intrauterine transfusion or delivery) in all eight fetuses with severe hemolytic disease. The umbilical vein diameter in the fetal liver was above normal in only one fetus, whereas the abdominal circumference was increased in only three of the eight severely affected fetuses. These data suggest that serial fetal liver ultrasound measurements may be useful as an adjunct to amniotic fluid analysis to predict the severely affected fetus in need of prompt intervention (intrauterine transfusion or delivery).

When cesarean section is not warranted because of extreme prematurity, continuous electronic fetal heart rate monitoring during the intrapartum period and in utero resuscitation of the distressed fetus are indicated, especially in cases of borderline fetal viability. Two cases are presented to illustrate the benefit of such measures when fetal distress occurs and the fetus is judged to be too small for operative intervention.

The relationship of three different fetal ponderal indexes was studied in 116 normal pregnancies between 20 and 41 weeks. All three fetal ponderal indexes were found to be independent of gestational age. Throughout normal gestation, the femur length to abdominal circumference ratio X 100 was found to be 22.3 +/- 2.4 (mean +/- 2 SD), the tibia length to abdominal circumference ratio X 100 19.3 +/- 2.2 (mean +/- 2 SD), and the femur plus tibia length to abdominal circumference ratio X 100 41.6 +/- 4.2 (mean +/- 2 SD). The clinical applications of the different fetal ponderal indexes in evaluating fetal growth are discussed. Because they are independent of gestational age, the fetal ponderal indexes should prove most useful in evaluating fetal growth in high-risk patients with unknown dates.

A modified fetal biophysical profile (nonstress test, fetal movements, fetal breathing movements, fetal tone, amniotic fluid volume, and placental grading) was serially assessed in 73 patients who presented with premature rupture of the membranes and were not in labor. The last study before delivery was compared with the outcome of pregnancy. The relationships between individual variables and combinations of variables (biophysical scoring) and the outcome of pregnancy--as reflected by the development of chorioamnionitis and/or neonatal sepsis--were determined. These data suggest that the fetal biophysical profile is a useful tool for evaluating patients with rupture of the membranes. Rupture of the membranes by itself does not alter the biophysical scoring of the healthy fetus; however, a low biophysical score (less than or equal to 7) was a good predictor of impending fetal infection in patients with premature rupture of the membranes.

Current techniques for estimating fetal weight in utero use equations containing biparietal diameter and abdominal circumference measurements. When a biparietal diameter cannot be obtained or its technical quality is poor, this technique is hindered. In this study, the use of the fetal femur length and abdominal circumference in estimating fetal weight was investigated. A new formula for estimation of fetal weight with a random error of 13.0 per cent is described.

The growth of the sonographically measured fetal thigh and fetal calf circumferences was studied during normal pregnancy. The normal range of fetal thigh and fetal calf circumferences for each week of pregnancy was determined from 20 to 41 weeks. The ratios of the ultrasonically measured fetal femur length to thigh circumference (expressed as femur length/thigh circumference X 100) and fetal tibia length to calf circumference (expressed as tibia length/calf circumference X 100) were also determined. These ratios were found to be relatively constant, with normal ranges after 20 weeks of 51.8 +/- 7.8 and 57.6 +/- 9.4 (mean +/- 2SD) respectively. The applications of these new fetal parameters in the evaluation of abnormal fetal growth patterns are discussed. It is suggested that these ratios should be used in evaluating fetal growth in high-risk patients who present late in pregnancy with unknown dates.

Amniotic fluid volume was serially assessed by real-time ultrasound in 90 patients who presented with premature rupture of the membranes (PROM) and not in labor. The degree of oligohydramnios was correlated to the outcome of pregnancy, as reflected by pregnancy prolongation, intrapartum fetal heart rate patterns consistent with umbilical cord compression, cesarean section rate, fetal distress, infection, and perinatal mortality rate. These data suggest that in patients with PROM the degree of oligohydramnios is positively correlated with unfavorable pregnancy outcome.

Described is a pregnancy complicated by pregnancy-induced hypertension, polyhydramnios, and obstructive renal failure due to an overdistended uterus. A review of the literature disclosed that only five such cases have been reported previously. Fetal outcome was generally related to the duration of gestation at the onset of polyhydramnios.