Second-trimester abortion by intramuscular 15-methyl-prostaglandin F2 alpha or intravaginal prostaglandin E2 suppositories: a randomized trial.

OBJECTIVE: To compare intramuscular (IM) prostaglandin 15 methyl-F2 alpha (15M-PGF2 alpha) with prostaglandin E2 (PGE2) vaginal suppositories for second-trimester abortion in terms of efficacy and side effects. METHODS: Fifty-one women were randomized to receive either 15M-PGF2 alpha IM injections or PGE2 intravaginal suppositories for second-trimester abortion. Efficacy and side effects of the two agents were analyzed by two-tailed t tests, chi 2 analysis with Fisher exact test, and survival analysis. RESULTS: The mean times to rupture of membranes, delivery of fetus, and delivery of placenta were significantly less for women receiving PGE2 vaginal suppositories. The cumulative abortion rate after 24 hours for the PGE2 group was 96%, compared with 69% for the 15M-PGF2 alpha group. Although there were few differences in side effects, the 15M-PGF2 alpha group had significantly fewer headaches, fevers, and chills. CONCLUSION: Intravaginal PGE2 is superior to IM 15M-PGF2 alpha for second-trimester abortion.

Efficacy of the biparietal diameter/femur length ratio to detect Down syndrome in patients with an abnormal biochemical screen.

Abnormal fetal biometry is considered a marker for fetal trisomy. We prospectively evaluated the biparietal diameter/femur length ratio to identify Down syndrome fetuses. This ratio was calculated when women (< 35 years old) underwent an amniocentesis for an abnormal biochemical screen for Down syndrome. Using reported ratio cut-offs (> 1.5 SD above the mean), the ratio had a sensitivity of 50% (3/6), specificity of 92% (244/264), positive predictive value of 13% (3/23), negative predictive value of 99% (244/247), and a relative risk of 10.8. Using our own population ratio, a cut-off > 1.5 SD had a sensitivity of 50% (3/6), specificity of 94% (249/252), positive predictive value of 17% (3/18), negative predictive value of 99% (249/252) and a relative risk of 13.9. A lower cut-off decreased the efficacy to detect Down syndrome. A ratio > 1.5 SD above the mean is a useful adjunct to identify Down syndrome in pregnancies at risk by an abnormal biochemical screen.

Variable clinical expression of mosaic trisomy 16 in the newborn infant.

Trisomy 16 is common in embryos and fetuses aborted early during development. Mosaicism for trisomy 16 is sometimes encountered during prenatal diagnosis, particularly with chorionic villi biopsy specimens, and, until recently, was thought to be confined to the placenta. However, recently, several liveborn infants with trisomy 16 mosaicism have been described. We report on an additional liveborn infant with trisomy 16 mosaicism and compare the clinical findings with those of the previously reported cases in an attempt to delineate a mosaic trisomy 16 syndrome. Cytogenetic analysis from our patient showed that there was a different proportion of abnormal cells in different tissues and that the anomaly was undetectable in blood lymphocyte cultures. This observation was consistent with some of the previous reports. DNA analysis of parents and child was carried out using a polymorphic dinucleotide marker that maps to the long arm of chromosome 16. This analysis showed that the extra chromosome 16 in the infant was maternal in origin and suggested that the nondisjunction was probably a first meiotic division error. Our results suggest that an investigation of multiple tissues is required before concluding that mosaicism is confined to the placenta. We conclude that a finding of trisomy 16 mosaicism at prenatal diagnosis should be regarded with extreme caution. This diagnosis may be associated with a highly variable phenotype that may occasionally be compatible with extrauterine life.

Ear length in second-trimester aneuploid fetuses.

OBJECTIVE: To test the hypothesis that small ears have diagnostic value in detecting second-trimester aneuploid fetuses by ultrasound. METHODS: We prospectively studied 452 patients with singleton pregnancies undergoing ultrasound examination for genetic amniocentesis at 14-25 weeks and an additional 30 singleton pregnancies at 20-25 weeks with a negative anomaly screen. Standard fetal biometry measurements were obtained, including ear length (from helix to end of lobe). RESULTS: Of these patients, 424 (88%) had ear measurements obtained, and a nomogram for ear length by gestational age was compiled. The relationship between ear length and gestational age was linear across the second trimester (r = 0.84, P < .001). Fourteen fetuses had aneuploidy by amniocentesis, of whom ten had ear lengths at or below the tenth percentile. The sensitivity was 71% and the specificity 92% (377 of 410). Positive and negative predictive values were 23% (ten of 43) and 99% (377 of 381), respectively. CONCLUSION: Fetal ear length may be useful in identifying aneuploid fetuses sonographically during the second trimester.

Comparison of humerus length with femur length in fetuses with Down syndrome.

A recent report by FitzSimmons et al. demonstrated a greater frequency of upper- versus lower-extremity shortening in autopsies of second-trimester fetuses with trisomy 21. We undertook this study to determine whether this upper-limb shortening could be detected by prenatal ultrasonography in the second trimester and therefore identify fetuses at risk for trisomy 21. A retrospective review of all prenatal sonograms preceding genetic amniocentesis was conducted. Between 1987 and 1990 11 consecutive fetuses between 15 and 22 weeks' gestation with trisomy 21 were identified by genetic amniocentesis. Femur and humerus lengths were plotted on growth curves created from 1470 normal patients between 12 and 26 weeks. Gestational age was confirmed by last menstrual period and biparietal diameter. In fetuses with trisomy 21, seven of 11 humeri were less than 5th percentile, for a sensitivity of 64%, whereas only two of 11 femurs were less than 5th percentile, for a sensitivity of 18%. Biparietal diameter/femur length and biparietal diameter/humerus length ratios were also tested to predict Down syndrome. In only 2 of 11 cases was the biparietal diameter/femur length ratio greater than 95th percentile, whereas the biparietal diameter/humerus length ratio was greater than 95th percentile in 7 of 11. Since all seven were identified by shortened humerus alone, we conclude that humerus length versus gestational age is the simplest and most effective screen. The positive predictive value of an abnormally short humerus length in detecting Down syndrome was 6.8% in our population where the prevalence of Down syndrome was 1 of 173. The present study supports the observations of FitzSimmons et al. that shortened humerus length has a greater sensitivity than femur length in cases of trisomy 21. We conclude that in fetuses at risk for trisomy 21 humerus length should be determined, because it may, if shortened, aid in the prenatal diagnosis.

Calculated risk of chromosomal abnormalities in twin gestations.

Genetic counseling concerning the risks of chromosomal abnormalities in twin gestations can be difficult; the risk of amniocentesis is weighed against that of chromosomal abnormalities in either one or both of the twins. Because most twins are dizygotic (each with a risk a priori of aneuploidy), the chance that one of the fetuses is affected is greater than would be expected for a singleton. Only three possibilities would result in either one or both twin's being affected: 1) dizygotic twins with one fetus affected, 2) dizygotic twins with both fetuses affected, and 3) monozygotic twins with both fetuses affected. Using existing tables of estimated risks of chromosomal abnormalities in singleton gestations and mathematically derived formulas, we created tables defining the age-related risks of chromosomal abnormalities in twin gestations. According to these tables, a patient at 33 years of age with a twin gestation has a risk of Down syndrome in at least one of her twins equivalent to that of a 35-year-old with a singleton. Prenatal genetic testing should be considered for women with twins at a younger age than the traditional 35.

Prenatal detection of a neural tube defect after fetal exposure to valproic acid.

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.