Revascularization of internal iliac arteries during aortoiliac surgery: a multicenter study

Prenatal screening for fetal abnormalities in an accepted part of modern obstetric management. Improvements on current screening procedures need to address increased diagnostic efficacy and earlier diagnosis. This study evaluates diagnostic efficacy of PAPP-A and F beta-hCG in the detection of first trimester pregnancy abnormalities, including Down syndrome (DS). Of 731 pregnant volunteers, obtained from a mature age population undergoing chorionic villus sampling (CVS), 17 DS and 11 compromised (six numerical (excluding sex chromosome) aneuploidies, five spontaneously failed) pregnancies were detected. Application of an algorithm, which combines PAPP-A and F beta-hCG levels with material age, detected 66.6 per cent of DS pregnancies for a five per cent false positive rate. Similarly, for a 1-2 per cent recall rate, 72.2 per cent of compromised pregnancies were detected. This report supports the notion that prenatal screening at 9-12 weeks of pregnancy is achievable with PAPP-A and F beta hCG quantitation. Whereas mid-gestational screening targetted the detection of fetal abnormalities, screening earlier in pregnancy will detect other pregnancy-related abnormalities, in addition to aneuploidy.     

Screening for fetal anomalies in the 12th week of pregnancy by transvaginal sonography in an unselected population

The advantages and limitations of transvaginal (TV) sonography in detecting fetal anomalies in the 12th week of pregnancy were examined in a prospective screening study of an unselected population. During a 3-year period, 3991 examinations were performed and 35 fetuses were identified as having 43 anomalies (0.9 per cent). Most of these malformations were either severe structural disorders or isolated nuchal changes when karyotyping revealed chromosomal aberration in six cases. Twenty-one pregnancies were terminated and three fetuses died. Routine transabdominal (TA) ultrasonographic examinations were performed at 18 and 30 weeks in all those pregnancies where the TV scan had not found fetal anomalies. TA sonography identified 19 abnormal fetuses and ten cases remained undetected. TV sonography detected 51 per cent of malformed fetuses which were diagnosed prenatally (not including cases with nuchal oedema) and 41 per cent of the total were found in this study. Besides offering the possibility of early termination, first trimester screening has the advantage of identifying a transient sonographic sign, nuchal oedema, which can be used as a marker in screening for fetal chromosomal abnormalities. However, standard mid-second-trimester TA scanning is still recommended, since a significant number of malformations cannot be detected so early in pregnancy.     

The outcome of pregnancies with confined placental chromosome mosaicism in cytotrophoblast cells

Cytogenetic findings and outcome of pregnancy are reported in 108 cases in which confined placental mosaicism (CPM, n = 101) or generalized mosaicism (n = 7) was found at or after first-trimester chorionic villus sampling. In all samples, a (semi)direct cytogenetic analysis of cytotrophoblast cells was performed. Two pregnancies with CPM ended in a spontaneous abortion before 28 weeks (1.9 per cent). In 15 cases the pregnancy was terminated: eight cases were shown to be examples of CPM; seven cases can be considered as examples of generalized mosaicism. A normal cytogenetic result was obtained after follow-up amniocentesis in 88 of the remaining 91 cases. In three cases, no amniocentesis was performed but confirmation of a normal karyotype was obtained in other cells. One of the 91 pregnancies was nevertheless terminated for psychosocial reasons. One child died perinatally and another on the seventh day after birth. The birth weight is known for 89 children; the curve shows a normal distribution. In 11 of these children (12.3 per cent), the birth weight was found to be below the tenth centile. The outcome in a subgroup of eight pregnancies with CPM and involvement of chromosome 13, 16, or 22, however, revealed two fetal losses and four children with a birth weight below the tenth centile (75 per cent).     

Assessment of the clinical usefulness of the 'Queenan' chart versus the 'Liley' chart in predicting severity of rhesus iso-immunization

In 1961 Liley developed a chart of changing amniotic fluid bilirubin levels (delta OD450) and gestation, with three zones delineating the severity of rhesus disease. This chart ranged from 27 to 40 weeks and was found to be clinically useful. Extrapolating the use of the Liley chart to earlier gestations however, was unsuccessful. Currently, cordocentesis is the only reliable means of assessing the fetal condition accurately prior to 27 weeks. In 1993, Queenan proposed a chart of delta OD450 from 14 to 40 weeks, with four zones to guide management. The aim of the current study is to assess the clinical usefulness of the 'Queenan' chart vs. the 'Liley' chart. There were 35 pregnancies affected by rhesus disease between 1990 and 1997 at the Mater Mothers' Hospital, Brisbane. The quantitative anti-D and delta OD450 levels obtained before intra-uterine transfusions were recorded. Each sample was labelled with the fetal condition at the time the sample was taken. Of the 72 delta OD450 samples, 36 (50 per cent) were performed before 27 weeks, and these included all four of the severely affected samples and 11 of the 13 moderately affected samples. The sensitivity of the Queenan chart in predicting the severely affected pregnancies was 100 per cent, with specificity of 79.4 per cent, positive predictive value of 22.2 per cent and negative predictive value of 100 per cent. For prediction of moderate/severely affected pregnancies, the sensitivity was 83.3 per cent, with specificity of 94.4 per cent, positive predictive value of 83.3 per cent and negative predictive value of 96.3 per cent. In conclusion, an delta OD450 chart which includes gestations less than 27 weeks is necessary with our changing caseload of rhesus iso-immunized patients, where severely affected pregnancies seemed to occur early and intervention even in moderately affected pregnancies seemed appropriate. We found that the Queenan chart is a suitable alternative to the Liley chart.     

Strong preference for non-invasive prenatal diagnosis in women pregnant through intracytoplasmic sperm injection (ICSI)

Intracytoplasmic sperm injection (ICSI) is a new and most powerful technique to treat severe forms of human infertility. While the follow-up studies have not shown an increased malformation risk so far, the genetic implications of ICSI are still not fully understood. For this reason, many institutions routinely recommend or even enforce invasive prenatal tests after successful intracytoplasmic sperm injection. We have counselled 107 women pregnant through ICSI about prenatal diagnosis. Sixty-five had already received genetic counselling prior to the treatment (group 1), while 42 had not attended our clinic before (group 2). They were free to choose between invasive and non-invasive diagnosis or no prenatal tests at all. Fifty-four per cent of these patients had an indication for prenatal karyotyping or other invasive procedures independent of ICSI. Only 17 per cent of the total cohort made use of amniocentesis or fetal blood sampling, 82 per cent opted for non-invasive tests (ultrasound, serum screening), and one couple did not wish any prenatal studies. The preference for non-invasive procedures was stronger in group 1 (94 per cent) than in group 2 (65 per cent). We suggest that if patients pregnant through ICSI have the option to choose freely between invasive and non-invasive prenatal tests, they strongly favour the latter.     

Serum screening of pregnant women reveals Down syndrome. Analysis of biochemical markers for earlier detection

Second trimester maternal serum screening for fetal Down's syndrome (DS), using the AFP (alpha-fetoprotein), hCG (human chorionic gonadotrophin) and uE3 (unconjugated oestriol) triple test, is as well documented procedure associated with a DS-detection rate of about 70 per cent, for an amniocentesis rate of about 7 per cent. The triple test is relatively little used in the Nordic countries, though its wider use would result in more efficient diagnosis of DS and various fetal malformtions. The maternal age indication currently used leaves gravidae under 35 years of age without prenatal diagnostics, although it is in just this age group that the majority (70 per cent) of cases of fetal DS occur. In Denmark, where 12 per cent of gravidae undergo invasive diagnostic procedures, the proportion of induced abortions due to the procedures is far too high, in relation to the DS detection rates obtained. Maternal serum screening yields a much better ratio between the risk of abortion after amniocentesis and the likelihood of DS detection than does maternal age alone. Maternal serum screening at 7-14 weeks of gestation, using pregnancy-associated plasma protein A and free hCG beta subunit concentrations, will become available within the next few years, thus reducing the incidence of some of the psychological and technical problems associated with second trimester screening, especially that of third trimester abortion. Irrespective of whether it is performed in the first or the second trimester, maternal serum screening will be the cornerstone of prenatal DS diagnosis in the future.     

Selective termination and elective reduction in twin pregnancies: 10 years experience at a single centre

Selective termination is employed in multifetal pregnancies, in the presence of an abnormal fetus, in order to improve the prognosis of the normal fetuses. The term elective reduction is used to describe reduction in twin pregnancies for maternal medical conditions, psychological, or socioeconomic reasons. The purpose of this study was to evaluate the factors that influence outcome in such pregnancies. Eighty-two twin pregnancies underwent selective termination (n = 59) or elective reduction (n = 23) over a 10-year period. Early procedures, performed < or = 14 weeks (n = 31), had a pregnancy loss of 9.7% and a mean procedure-to-loss interval of 4.1 +/- 2.8 weeks; mean birthweight was 3299 +/- 395 g in survivors, with a mean gestational age at delivery of 38.4 +/- 2.3 weeks. In comparison, procedures performed > 14 weeks (n = 51) had a pregnancy loss of 7.8%, with a procedure-to-loss interval of 1.2 +/- 0.6 weeks. Mean birthweight was 2577 +/- 999 g, with a mean gestational age at delivery of 35.7 +/- 5 weeks. In conclusion, outcomes were more favourable among patients who underwent a first trimester procedure. The slight increase in pregnancy loss may be attributed to a higher than expected rate of spontaneous abortions in the first trimester, as manifested by the higher procedure-to-loss interval after a first trimester procedure. These facts underscore the importance of early detection of fetal abnormalities in twin pregnancies by ultrasonography and chorionic villus sampling.     

Notifying women of the results of their cervical smear tests by mail: does it result in a decreased loss to follow-up of abnormal smears?

We undertook a prospective randomised intervention study of the proportions of women with abnormal cytology results who were lost to follow-up in 42 general practices in urban and rural Queensland over 26 weeks. Practices in the intervention group were provided with a redesigned cervical smear request form that allowed patients to provide an address for direct notification from the laboratory by mail. Satisfaction questionnaires sent to the general practitioners in the intervention group showed that most made at least some use of direct notification, and most felt it was worthwhile. For women with an initial result of cervical intraepithelial neoplasia (CIN), there was a loss to follow-up of 23 per cent (95 per cent confidence interval (CI) 11 to 39) among the control group compared to none in the intervention group (upper CI 7 per cent), a highly significant difference (P < 0.001). Mailing cervical screening results to women may reduce the loss to follow-up of those with CIN findings.     

Karyotyping of fetal cells in the prenatal diagnosis in Costa Rica

The results of 182 genetic amniocenteses between 14 and 37 weeks gestation, from 1986 to 1992, and of two cordocenteses in 1992, are reported. There were two main reasons for referral: maternal age 35 years and older and abnormal ultrasound assessment. Fetal cells were closed cultured and mass harvested. In 3.7% of cases fetal chromosomes were defective. Turn around time was about three weeks up to and including 1991 and two weeks in 1992, culture failure rate was 7% that year. No cytogenetic misdiagnosis and no complication or sequelae related to the amniocenteses were detected. We conclude this is a safe and reliable procedure to obtain fetal karyotypes and to improve obstetric management of high-risk pregnancies.     

Quantitative study on the effect of osthole on proximal tibiae in ovariectomized (OVX) rats

OBJECTIVE: To determine if a correlation exists between the level of maternal serum alpha-fetoprotein (MSAFP) elevation and the rate of adverse pregnancy outcome, to examine the timing of pregnancies ending in fetal or neonatal death, and to develop a protocol for antepartum surveillance in an effort to prevent these adverse outcomes. STUDY DESIGN: Singleton pregnancies with a single second-trimester elevated MSAFP > or = 2.0 multiples of the median (MoM) were eligible if a targeted ultrasound evaluation (< 24 weeks) was in agreement with the dates and no fetoplacental anomaly was detected. Three groups were established based on the second-trimester MSAFP elevation: 2.0-2.49, 2.5-2.99 and > or = 3.0 MoM. RESULTS: Among the 383 patients enrolled, delivery data were available on 333 infants. Stratified by MSAFP elevations of 2.0-2.49, 2.5-2.99 and > or = 3.0 MoM, the rates of adverse pregnancy outcome were: (1) preterm birth: 14.3%, 15.6%, 20.3%; (2) small for gestational age at birth: 7.4%, 11.1%, 22.2%; and (3) perinatal deaths (neonatal and fetal): 2.6%, 3.3%, 5.6%. Seven pregnancy losses (three neonatal and four fetal deaths) occurred prior to 28 weeks. Of these seven, six fetuses exhibited intrauterine growth retardation by 23-26 weeks' gestation, and five of six were associated with MSAFP levels > or = 2.5 MoM. Four losses (two neonatal and two fetal deaths) occurred after 28 weeks. Of these, three involved structurally normal infants with normal growth who died after 34 weeks. All three of these pregnancies exhibited MSAFP elevations < 2.5 MoM. CONCLUSION: In pregnancies with an unexplained elevated second-trimester MSAFP, the rate of adverse pregnancy outcomes is increased with higher elevations. Any proposed program to improve pregnancy outcome in patients with unexplained MSAFP elevations must include efforts aimed at preventing preterm delivery, repeat ultrasound at 24-26 weeks to rule out early-onset intrauterine growth retardation in pregnancies with elevations > or = 2.5 MoM and fetal biophysical monitoring, even in normally grown fetuses, instituted at 32 weeks to detect fetuses at risk for intrauterine death.     

Fetal cardiac measurements derived by transvaginal and transabdominal cross-sectional echocardiography from 14 weeks of gestation to term

OBJECTIVE: Most of the routine ultrasound screening in our institution consists of early transvaginal examinations at 14-17 weeks. Complete fetal echocardiography is performed in every case. However, normal values for most fetal cardiac structures at this stage of gestation are not available. Our aim was to construct normal ranges for fetal cardiac structures, derived from cross-sectional echocardiography, at 14-40 weeks of gestation. DESIGN: A prospective study was performed. The study group consisted of 637 pregnant women referred for a routine sonographic examination. Women with abnormal prenatal or postnatal outcome were not included in the study. Transvaginal examinations were used for 14-17 weeks of gestation. More advanced pregnancies were examined transabdominally. RESULTS: We constructed normal ranges for the left and right end-diastolic transverse ventricular diameters (n = 637), left/right ventricular ratio (n = 637), aortic root diameter (n = 637), pulmonary artery diameter (n = 637), aortic/pulmonary ratio (n = 490), left and right transverse atrial diameters (n = 201) and left/right atrial ratio (n = 201). CONCLUSIONS: The results provide the examiner with normal ranges for fetal cardiac structures for the early transvaginal examination. The continuity of all curves from 14 to 40 weeks of gestation allows follow-up of any specific fetus to term.     

Prenatally diagnosed fetal ventriculomegaly; prognosis and outcome

The purpose of the present study was to determine the postnatal outcome and prognostic factors of prenatally diagnosed ventriculomegaly, and to establish the relationship between prenatal sonographic measurements and postnatal psychomotor development. A total of 42 singleton pregnancies with sonographically determined fetal ventriculomegaly at 20-38 weeks' gestation were reviewed, together with follow-up data on postnatal outcome at a mean of 29 months after delivery. Sonographic measurements included head circumference, cerebral lateral ventricular diameter at the anterior and posterior horn level, and hemisphere diameter. Classification of psycho-motor development consisted of assessment of motoric behaviour, speech, communication and social skills ('Van Wiechen' classification). Perinatal mortality rate was 38 per cent, of which half were directly associated with cephalocentesis. Only the ventricle/hemisphere ratio for the anterior and posterior horn of the lateral cerebral ventricles was significantly higher among perinatal deaths than amongst the survivors. Within the subset of survivors (n = 26), psycho-motor development was normal in 46 per cent. Postnatal examination revealed syndrome anomalies in five infants, of which four were associated with psycho-motor retardation. Prenatally diagnosed ventriculomegaly has a poor postnatal outcome with more than 50 per cent of the live-born infants demonstrating abnormal psycho-motor development. The predictive value of fetal biometric measurements is poor. The presence of syndromal anomalies emphasizes the need for genetic counselling in future pregnancies.     

Hormonal profiles of early gestations with abnormal karyotype

OBJECTIVE: To describe the hormonal profiles of chromosomally abnormal pregnancies during the first trimester. DESIGN: A prospective study from 1984 through 1990 in which infertility patients who conceived were monitored weekly with serum E2, P, and beta-hCG levels. SETTING: The infertility practice at Rush-Presbyterian-St. Luke's Medical Center in Chicago, Illinois. PATIENTS: Study included 15 women who had dilatation and curettage for first trimester fetal losses with confirmed abnormal karyotype, 6 women with chromosomally normal male abortuses, and 60 consecutive women whose pregnancies yielded normal term infants. RESULTS: After natural conception, E2 demonstrated a moderate rise in both normal and chromosomally abnormal pregnancies to approximately 300 pg/mL by day 29 (6 weeks of gestation). In normal gestations, E2 continued a steady increase to exceed the level of 1,000 pg/mL by day 64 (11 weeks of gestation). In chromosomally abnormal pregnancies, the mean E2 plateaued and remained at approximately 200 pg/mL until fetal demise was noted. In stimulated conceptions, the rise of E2 was sharp and early (1,200 pg/mL by day 29); in normal pregnancies, E2 steadily increased to an average of 1,400 pg/mL by the end of the first trimester, whereas in karyotypically abnormal gestations, E2 declined to approximately 200 pg/mL by day 64. In pregnancies yielding a male abortus, a sharp decline and plateau at 800 pg/mL by day 56 (10 weeks of gestation) was observed. In both natural and stimulated normal pregnancies, hCG levels first demonstrated a linear rise, followed by a curvilinear increase from day 29 until day 56, with a peak of approximately 110,000 mIU/mL. The beta-hCG in chromosomally abnormal pregnancies, as well as in pregnancies yielding a male abortus, was characterized by a slow and gradual rise to a maximum of 40,000 mIU/mL, which remained relatively linear until day 64 when fetal demise was detected in all cases. Progesterone level data were excluded from analysis because of frequent P supplementation. CONCLUSIONS: There were significant differences in the hormonal profiles of chromosomally normal and abnormal pregnancies. Serial measurements of serum E2 and beta-hCG from the 6th week of gestation may be useful in predicting an abnormal karyotype sooner than other current diagnostic tests.     

Beyond signing the death certificate

Progressively since 1982 and as part of a nationwide programme for the diagnosis and prevention of genetic diseases, maternal serum alpha-fetoprotein (MS-AFP) screening and ultrasound fetal monitoring has been implemented in all pregnant women in Cuba. In Havana City, 328,983 pregnant women underwent MS-AFP screening between 15 and 19 weeks of gestational age. With a cut-off level of > or = 2 multiples of the normal median (MOM), 1767 amniocenteses were carried out to determine the levels of amniotic fluid AFP and 685 malformed fetuses were diagnosed. By ultrasound fetal monitoring, an additional 686 malformed fetuses were detected. As a result of the programme, the birth prevalence of neural tube defects has fallen by 90 per cent.     

Growth of infants and young children born small or large for gestational age: findings from the Third National Health and Nutrition Examination Survey

An allele-specific polymerase chain reaction (ASPCR) assay for prenatal genotyping of the Kidd antigen system in order to identify pregnancies at risk for haemolytic disease of the newborn (HDN) was developed. Oligonucleotide primers were designed for ASPCR of JKA and JKB. A validation study was performed using DNA isolated from 54 serotyped whole blood samples and 8 amniocentesis samples. A concordance rate of 100 per cent was observed between serotyping and ASPCR detection of the JKA and JKB alleles. Experiments were conducted to quantify the maternal contamination that could be tolerated in Kidd ASPCR assays. The sensitivity of this assay ranged from 0.2 per cent when detecting the presence of JKB and JKA background, to 2 per cent for detecting the presence of JKA in a JKB background. This sensitive assay is particularly useful for rapid genotyping of fetal amniotic cells to identify pregnancies at risk for HDN due to incompatibilities within the Kidd blood group system.     

Randomised study of risk of fetal loss related to early amniocentesis versus chorionic villus sampling

BACKGROUND: Several cohort studies have shown the feasibility of early amniocentesis (between 11 and 13 weeks of gestation) as an alternative to chorionic villus sampling (CVS) for karyotyping, but the only completed randomised study of fetal safety showed a significant fetal-loss risk related to first-trimester amniocentesis. We assessed fetal safety in early amniocentesis and CVS. METHODS: We assessed early amniocentesis at 11-13 weeks gestational age compared with the fetal risk associated with CVS at 10-12 weeks. 1160 pregnant women were randomly assigned one procedure (581 early amniocentesis, 579 CVS) after a baseline ultrasound examination at 10 weeks' gestation and were followed up until birth. Total fetal loss and neonatal morbidity were the primary outcome measures. Sampling success and pregnancy complications were secondary outcomes. We used a filter to increase the cell yield in the early amniotic-fluid samples. CVS was transabdominal. FINDINGS: We found a significantly increased occurrence of talipes equinovarus in the early amniocentesis group (p < 0.01), the risk of which was associated with sampling at the earliest gestational ages and with temporary leakage of amniotic fluid after sampling. Therefore, the trial was stopped early, which reduced the power of the safety study. 4.8% (27) of fetuses in the CVS group and 5.4% (30) in the early amniocentesis group were lost after randomisation (p = 0.66). More detailed survival analysis did not show any significant differences in fetal loss rates. Leakage of amniotic fluid after sampling occurred significantly more frequently after early amniocentesis than after CVS (p < 0.001), but we found no other major differences in pregnancy complications. Significantly more CVS than early amniocentesis procedures were repeated or failed to produce a karyotype (p < 0.01). INTERPRETATION: Even though the numbers were small, we found an association between early amniocentesis and talipes equinovarus. We believe this association to be true, since it supports a trend in a similar randomised study. Our results show that early amniocentesis, when done with the filter technique, is associated with an abortion risk similar to CVS, although the limited size of our study population reduced the strength of this conclusion.     

Cytogenetic and molecular genetic characterization of trisomy 20 mosaicism in fetal blood and tissues

We report a case of mosaic trisomy 20, the most common autosomal mosaicism identified in amniocytes, ascertained in a woman referred for amniocentesis because of abnormal ultrasound at 18.1 weeks' gestation which revealed short femurs and nuchal thickening. Metaphase analysis of 98 clones revealed 47,XY, +20 in 96 cells (98 per cent). Trisomy 20 was demonstrated in 6 cells (12 per cent) in a total of 50 cells from two fetal blood cultures obtained after pregnancy termination. Fluorescence in situ hybridization (FISH) analysis of interphase nuclei utilizing a chromosome 20 alpha-satellite centromeric DNA probe revealed three signals in 57/546 nuclei (10 per cent) in fetal blood. Metaphase analysis of 167 cells from seven different fetal tissue sources revealed trisomy 20 in 32 cells (19.2 per cent). The percentage of trisomy 20 cells varied with tissue type, with the highest percentage (13/25 cells, 52 per cent) identified in the small intestine and lymph nodes and the lowest percentage (1/34 cells, 2.9 per cent) identified in a specimen of chorionic villi. Molecular genetic analyses utilizing polymerase chain reaction (PCR)-formated dinucleotide repeat polymorphisms demonstrated that the non-disjunctional event most likely occurred post-zygotically and that the origin of the extra chromosome 20 was maternal. This study is the first to demonstrate trisomy 20 cells in fetal blood, suggesting that mosaic trisomy 20 can be embryonic in origin. In cases of prenatally detected mosaic trisomy 20, examination of fetal blood should be considered, as well as study of placental membranes, skin, and urine sediment to confirm the karyotype and determine its significance.     

Outpatient termination of pregnancy

Termination of pregnancy was performed under local anaesthesia as an outpatient procedure on 251 patients. The gestational ages ranged from 5 to 12 weeks. Either the portable Karman curette equipment or the syringe kits were used. The incidence of complications was low. Only 6 per cent of patients would have preferred general anaesthesia. The optimal gestational age at which to terminate pregnancies appeared to be between 6 and 10 weeks. Ninety-one per cent of patients used effective contraception after the termination.     

The use of second-trimester genetic sonogram in guiding clinical management of patients at increased risk for fetal trisomy 21

OBJECTIVE: To test the efficacy of ultrasound in detecting fetuses with trisomy 21. METHODS: From November 1, 1992, to December 31, 1995, a second-trimester genetic sonogram was offered to all women with singleton fetuses at increased risk (at least 1:274) for trisomy 21, who had either declined genetic amniocentesis or chose to have a sonogram before deciding whether to undergo an amniocentesis. In addition to standard fetal biometry, the following ultrasound markers for aneuploidy were evaluated: structural anomalies (including face, hands, and cardiac [four-chamber view and outflow tracts]), short femur, short humerus, pyelectasis, nuchal fold thickening, echogenic bowel, choroid plexus cysts, hypoplastic middle phalanx of the fifth digit, wide space between the first and second toes, and two-vessel umbilical cord. Outcome information included the results of genetic amniocentesis, if performed, or the results of postnatal pediatric assessment and follow-up. RESULTS: Five hundred seventy-three patients had a genetic sonogram between 15 and 23 weeks' gestation: 378 patients had advanced maternal age (at least 35 years), 141 had abnormal serum biochemistry, and 54 had both. The majority (495, or 86.3%) had a normal genetic sonogram (absence of abnormal ultrasound markers); 51 (9%) had one marker present, and 27 (4.7%) had two or more markers present. Outcome was obtained on 422 patients (the remaining were ongoing pregnancies or were lost to follow-up). Twelve of 14 fetuses with trisomy 21, one fetus with trisomy 13, and one fetus with triploidy had two or more abnormal ultrasound markers present; one fetus with trisomy 21 had one abnormal marker and one had a completely normal ultrasound. When one or more abnormal ultrasound markers were present, the sensitivity, specificity, and positive and negative predictive values for trisomy 21 were 92.8%, 86.7%, 19.4%, and 99.7%, respectively. When two or more abnormal ultrasound markers were present, the corresponding values were 85.7%, 96.8%, 48%, and 99.5%. In the study population, the amniocentesis rate was 12.7% overall and 17.3% in cases with known outcome. CONCLUSION: Second-trimester genetic sonogram may be a reasonable alternative for patients at increased risk for fetal trisomy 21 who wish to avoid amniocentesis. In experienced hands, this approach may result in a high detection rate of trisomy 21 (93%), with an amniocentesis rate of less than 20%.