The prenatal diagnosis of Dandy-Walker variant should not be made before 18 weeks gestation because the development of the cerebellar vermis may be incomplete at that time.

These sonographic markers seem to be sensitive for the detection of chromosomal abnormalities.

Most previously published tables of birth weight percentiles as a function of gestational age have been derived from neonates with imprecise gestational dating. In order to improve the accuracy of neonatal birth weight percentiles, we developed a birth weight table based on measurements from a group of neonates who had accurate gestational dating by prenatal first trimester ultrasonography. By matching a database of obstetrical ultrasonograms over a 5 year period to birth records at our institution, 3718 newborn infants with gestational dating by first trimester ultrasonography were identified. Statistical smoothing and regression techniques were applied to gestational age at birth and birth weight data to develop a table for the 10th, 50th, 90th, and other weight percentiles for 25 weeks of gestation onward. The weight table developed from our population has lower 50th and 90th percentile weights, and narrower 10th to 90th percentile ranges, at 25 to 35 weeks than in prior tables. At 39 to 43 weeks, our 10th, 50th, and 90th percentile weights are higher than those in previous tables. Our weight table for newborn infants, based on measurements from neonates with accurate dating, permits improved assignment of weight percentiles for gestational age and more accurate diagnosis of growth disorders in fetuses and neonates.

No abstract

Choroid plexus (CP) cysts have been associated with trisomy 18, although most fetuses with CP cysts are normal. Since many fetuses with trisomy 18 have other sonographic abnormalities, the necessity of obtaining a karyotype for all fetuses with isolated CP cysts remains controversial. The authors prospectively studied 234 second-trimester fetuses with sonographically discovered CP cysts. Two hundred twenty of them had no other sonographic findings. None of these 220 normal fetuses had evidence of aneuploidy at amniocentesis or an anomaly at birth. Fourteen fetuses had major anomalies detected in utero: 11 had trisomy 18, one had triploidy, and two had normal karyotypes but were structurally abnormal. While size and bilaterality of the CP cysts were not helpful in predicting aneuploidy, the meticulous anatomic survey of fetuses with CP cysts allowed successful identification of all aneuploid fetuses. These data show that the yield of abnormal karyotypes in fetuses with isolated CP cysts is low and may not justify the risk of amniocentesis.