Accuracy of prenatal diagnosis of isolated aqueductal stenosis

OBJECTIVE

The objective of this article is to determine the success rate of prenatally diagnosed isolated aqueductal stenosis (AS) as a first step in an evidence-based reassessment of ventriculoamniotic shunting for isolated AS.

METHODS

Cases of ventriculomegaly at Magee-Womens Hospital between 2006 and 2013 were ascertained. AS was suspected when prenatal ultrasound and magnetic resonance imaging (MRI) demonstrated signs of pressure hydrocephalus. The prenatal diagnosis generated by ultrasound and MRI was compared with the postnatal diagnosis based upon neonatal neuroimaging.

RESULTS

The initial query of the Magee-Womens Hospital database resulted in 370 cases of ventriculomegaly. After exclusion for associated central nervous system malformations, 110 cases of severe ventriculomegaly remained. The imaging studies on each fetus were reviewed, and cases of prenatally diagnosed AS were identified. The median gestational age of the ultrasound diagnosis and prenatal MRI was 23 weeks 3 days and 33 weeks 3 days, respectively. All cases of prenatally suspected isolated AS (six of six) and cases of AS with other associated central nervous system anomalies (six of six) were correctly identified.

CONCLUSION

An accurate prenatal diagnosis of isolated fetal AS is possible. This is an important first step in an evidence-based reassessment of ventriculoamniotic shunting for isolated AS. © 2014 John Wiley & Sons, Ltd.

High resolution non-invasive detection of a fetal microdeletion using the GCREM algorithm

BACKGROUND/OBJECTIVE

The non-invasive prenatal detection of fetal microdeletions becomes increasingly challenging as the size of the mutation decreases, with current practical lower limits in the range of a few megabases. Our goals were to explore the lower limits of microdeletion size detection via non-invasive prenatal tests using Minimally Invasive Karyotyping (MINK) and introduce/evaluate a novel statistical approach we recently developed called the GC Content Random Effect Model (GCREM).

METHODS

Maternal plasma was obtained from a pregnancy affected by a 4.2-Mb fetal microdeletion and three normal controls. Plasma DNA was subjected to capture an 8-Mb sequence spanning the breakpoint region and sequence. Data were analyzed with our published method, MINK, and a new method called GCREM.

RESULTS

The 8-Mb capture segment was divided into either 38 or 76 non-overlapping regions of 200 and 100 Kb, respectively. At 200 Kb resolution, using GCREM (but not MINK), we obtained significant adjusted p-values for all 20 regions overlapping the deleted sequence, and non-significant p-values for all 18 reference regions. At 100 Kb resolution, GCREM identified significant adjusted p-values for all but one 100-Kb region located inside the deleted region.

CONCLUSION

Targeted sequencing and GCREM analysis may enable cost effective detection of fetal microdeletions and microduplications at high resolution.

Mannose binding lectin genotypes are not associated with increased risk of unexplained recurrent pregnancy loss

PURPOSE

Immune response to infections has been associated with recurrent pregnancy loss (RPL). Low plasma mannose binding lectin (MBL) levels, an innate immunity factor in infections, has been related to RPL. In this study, we tested the hypothesis that MBL genotypes that are known to cause reduced plasma MBL levels are significantly more frequent among women experiencing unexplained RPL.

METHODS

This study included 219 Caucasian women diagnosed with unexplained RPL and 236 control women. All participants were genotyped for two promoter (-550 C > G and -221 G > C) and three missense (R52C, G54D and G57E) mutations in exon 1. These mutations are known to be associated with variations in plasma MBL levels. Genotype frequencies were estimated by gene counting and were compared to the expectation of Hardy-Weinberg equilibrium by chi-squared (X(2)) analysis and Fisher's exact test. Allele and genotype frequencies were compared in cases and controls using X(2) contingency table analysis.

RESULTS

There was no difference in demographics between cases and controls. The number of miscarriages in the participants with RPL ranged from 2 to 10 spontaneous abortions (SAB's) per participant. Populations genotyped were in Hardy-Weinberg equilibrium. There was no association between a history of RPL and multi-SNP genotypes at the MBL locus. In unexplained RPL, the number of SAB's and live birth rates were unaffected by MBL genotype. There was no association between MBL genotype and the risk of unexplained RPL. The occurrence of live birth was not associated with MBL genotype.

CONCLUSION

Genotypes known to cause low MBL plasma levels are not associated with an increased risk of unexplained RPL.

Structural and regulatory characterization of the placental epigenome at its maternal interface

Epigenetics can be loosely defined as the study of cellular "traits" that influence biological phenotype in a fashion that is not dependent on the underlying primary DNA sequence. One setting in which epigenetics is likely to have a profound influence on biological phenotype is during intrauterine development. In this context there is a defined and critical window during which balanced homeostasis is essential for normal fetal growth and development. We have carried out a detailed structural and functional analysis of the placental epigenome at its maternal interface. Specifically, we performed genome wide analysis of DNA methylation in samples of chorionic villus (CVS) and maternal blood cells (MBC) using both commercially available and custom designed microarrays. We then compared these data with genome wide transcription data for the same tissues. In addition to the discovery that CVS genomes are significantly more hypomethylated than their MBC counterparts, we identified numerous tissue-specific differentially methylated regions (T-DMRs). We further discovered that these T-DMRs are clustered spatially along the genome and are enriched for genes with tissue-specific biological functions. We identified unique patterns of DNA methylation associated with distinct genomic structures such as gene bodies, promoters and CpG islands and identified both direct and inverse relationships between DNA methylation levels and gene expression levels in gene bodies and promoters respectively. Furthermore, we found that these relationships were significantly associated with CpG content. We conclude that the early gestational placental DNA methylome is highly organized and is significantly and globally associated with transcription. These data provide a unique insight into the structural and regulatory characteristics of the placental epigenome at its maternal interface and will drive future analyses of the role of placental dysfunction in gestational disease.

Gene expression in first trimester preeclampsia placenta

BACKGROUND

The goal of this study was to further validate eight candidate genes identified in a microarray analysis of first trimester placentas in preeclampsia.

MATERIAL AND METHOD

Surplus chorionic villus sampling (CVS) specimens of 4 women subsequently diagnosed with preeclampsia (PE) and 8 control women (C) without preeclampsia analyzed previously by microarray and 24 independent additional control samples (AS) were submitted for confirmatory studies by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Downregulation was significant in FSTL3 in PE as compared to C and AS (p = .04). PAEP was downregulated, but the difference was only significant between C and AS (p = .002) rather than between PE and either of the control groups. Expression levels for CFH, EPAS1, IGFBP1, MMP12, and SEMA3C were not statistically different among groups, but trends were consistent with microarray results; there was no anti-correlation. S100A8 was not measurable in all samples, probably because different probes and primers were needed.

CONCLUSIONS

This study corroborates reduced FSTL3 expression in the first trimester of preeclampsia. Nonsignificant trends in the other genes may require follow-up in studies powered for medium or medium/large effect sizes. qRT-PCR verification of the prior microarray of CVS may support the placental origins of preeclampsia hypothesis. Replication is needed for the candidate genes as potential biomarkers of susceptibility, early detection, and/or individualized care of maternal-infant preeclampsia.

Statistical considerations for digital approaches to non-invasive fetal genotyping

MOTIVATION

A growing body of literature has demonstrated the potential for non-invasive diagnosis of a variety of human genetic diseases using cell-free DNA extracted from maternal plasma samples in early gestation. Such methods are of great significance to the obstetrics community because of their potential use as clinical standard of care. Proof of concept for such approaches has been established for aneuploidy and paternally inherited dominant traits. Although significant progress has recently been made, the non-invasive diagnosis of monogenic diseases that segregate in a recessive mendelian fashion is more problematic. Recent developments in microfluidic digital PCR and DNA sequencing have resulted in a number of recent advances in this field. These have largely, although not exclusively, been used for the development of diagnostic methods for aneuploidy. However, given their prevalence, it is likely that such methods will be utilized towards the development of non-invasive methods for diagnosing monogenetic disorders.

RESULTS

With this in mind, we have undertaken a statistical modeling of three contemporary (digital) analytical methods in the context of prenatal diagnosis using cell free DNA for monogenic diseases that segregate in a recessive mendelian fashion. We provide an experimental framework for the future development of diagnostic methods in this context that should be considered when designing molecular assays that seek to establish proof of concept in this field.

Altered global gene expression in first trimester placentas of women destined to develop preeclampsia

BACKGROUND

Preeclampsia is a pregnancy-specific disorder that remains a leading cause of maternal, fetal and neonatal morbidity and mortality, and is associated with risk for future cardiovascular disease. There are no reliable predictors, specific preventative measures or treatments other than delivery. A widely held view is that the antecedents of preeclampsia lie with impaired placentation in early pregnancy. Accordingly, we hypothesized dysregulation of global gene expression in first trimester placentas of women who later manifested preeclampsia.

METHODS

Surplus chorionic villus sampling (CVS) tissues were collected at 10-12 weeks gestation in 160 patients with singleton fetuses. Four patients developed preeclampsia, and their banked CVS specimens were matched to 8 control samples from patients with unaffected pregnancies. Affymetrix HG-U133 Plus 2.0 GeneChips were utilized for microarray analysis. Naïve Bayes prediction modeling and pathway analysis were conducted. qRT-PCR examined three of the dysregulated genes.

RESULTS

Thirty-six differentially expressed genes were identified in the preeclampsia placentas. qRT-PCR verified the microarray analysis. Thirty-one genes were down-regulated. Many were related to inflammation/immunoregulation and cell motility. Decidual gene dysregulation was prominent. No evidence was found for alterations in hypoxia and oxidative stress regulated genes.

CONCLUSIONS

To our knowledge, this is the first study to show dysregulation of gene expression in the early placentas of women approximately 6 months before developing preeclampsia, thereby reinforcing a placental origin of the disorder. We hypothesize that placentation in preeclampsia is compromised in the first trimester by maternal and fetal immune dysregulation, abnormal decidualization, or both, thereby impairing trophoblast invasion. Several of the genes provide potential targets for the development of clinical biomarkers in maternal blood during the first trimester. Supplementary materials are available for this article via the publisher's online edition.

Recurrent spontaneous abortion and skewed X-inactivation: is there an association?

OBJECTIVE

The purpose of this study was to determine whether there is an association between skewed X-inactivation and recurrent spontaneous abortion in a large, well-defined sample of women with recurrent loss.

STUDY DESIGN

X-chromosome inactivation patterns were compared in 5 groups of women. Group 1 (recurrent spontaneous abortion) consisted of 357 women with 2 or more spontaneous losses. In group 2 (infertility), there were 349 subjects from infertility practices recruited at the time of a positive serum beta-human chorionic gonadotropin. Group 3 (spontaneous abortion) women (n = 81) were recruited at the time of an ultrasound diagnosis of an embryonic demise or an anembryonic gestation. Groups 4 (primiparous) and 5 (multiparous) were healthy pregnant subjects previously enrolled in another study to determine the incidence and cause of pregnancy complications, such as preeclampsia and intrauterine growth restriction. The Primiparous group included 114 women in their first pregnancy, whereas the Multiparous group consisted of 79 women with 2 or more pregnancies but without pregnancy loss.

RESULTS

The rate of extreme skewing (90% or greater) in the recurrent spontaneous abortion population was 8.6%, and not statistically different from any of the other groups, except the Primiparous group (1.0%, P < .01). The incidence of X-inactivation skewing of 90% or greater was no different whether there had been at least 1 live birth (9.9%), or no previous live births and at least 3 losses (5.6%, P > .05). When age and skewing of 90% or greater are compared, subjects with extreme skewing have a mean age of 2 years older than those without extreme skewing (P < .05).

CONCLUSION

Skewed X-inactivation is not associated with recurrent spontaneous abortion but is associated with increasing maternal age.

Variable outcomes in mosaic trisomy 16: five case reports and literature analysis

OBJECTIVES

To report five cases of mosaic trisomy 16 with variable outcomes in the context of the literature on mosaic trisomy 16. Complications in these cases include preeclampsia, IUGR, fetal anomalies, and death, with no predictable pattern.

METHODS

Observation of five new cases and statistical analysis of 125 reported cases of mosaic trisomy 16 with prenatal detection and outcome data.

RESULTS

(1) IUGR, premature delivery, and/or physical anomalies are observed commonly, even when the trisomy is thought to be confined to the placenta; (2) Level II mosaicism for trisomy 16 in amniotic fluid may reflect a true mosaic state with phenotypic consequences; (3) FISH is more sensitive than traditional cytogenetics in detecting mosaicism in all tissue types examined; (4) hCG levels can be extremely elevated, and MS-AFP levels are often elevated; and (5) Uniparental disomy (UPD) increases the rates of IUGR and physical anomalies in CPM cases.

CONCLUSION

While there is no obvious mosaic trisomy 16 syndrome, IUGR and heart defects commonly occur, even if the mosaicism appears to be confined to the placenta. A completely normal outcome occurs only in about 20% of the cases; however, complications can often be limited to prematurity, small-for-gestational-age infants, and/or minor or surgically reparable birth defects.

Elevated first-trimester nuchal translucency increases the risk of congenital heart defects

OBJECTIVE

We sought to evaluate the association between first trimester nuchal translucency measurement and the risk for major congenital heart defect in chromosomally normal fetuses.

STUDY DESIGN

First trimester (10 weeks 4 days of gestation to 13 weeks 6 days of gestation) nuchal translucency was obtained in a large prospective multicenter National Institute of Child Health and Human Development study for Down syndrome prediction. The study, which was conducted between May 1998 and December 2000, was restricted to singleton pregnancies. Gestational age was determined by crown rump length measurements. Perinatal outcomes were determined and included the frequency of major congenital heart defect, which was defined as those cases that potentially could require surgery, intensive medical therapy, or prolonged follow-up time. Logistic regression analysis was used to determine whether nuchal translucency was a significant predictor of congenital heart defect.

RESULTS

There were 8167 chromosomally normal pregnancies, of which 21 cases of major congenital heart defect were identified at follow-up examination (incidence, 2.6/1000 pregnancies). The risk of congenital heart defect rose with increasing nuchal translucency measurements. The mean nuchal translucency value for the normal and congenital heart defect groups were 1.5 mm and 1.9 mm, respectively (P = .05). With a nuchal translucency measurement of < 2.0 mm, the incidence of congenital heart defect was 13 of 6757 pregnancies (1.9 of every 1000 pregnancies). At 2.0 to 2.4 mm, the incidence was 5 of 1032 pregnancies (4.8 of every 1000 pregnancies). At 2.5 to 3.4 mm, the incidence was 2 of 335 pregnancies (6.0 of every 1000 pregnancies). At > or = 3.5 mm, the incidence was 1 of 43 pregnancies (23 of every 1000 pregnancies). Logistic regression analysis confirmed that nuchal translucency was associated significantly with congenital heart defect (odds ratio, 2.1; 95% CI, 1.4-3.1; P = .0004).

CONCLUSION

Increased first trimester nuchal translucency measurement was associated with a higher risk of major congenital heart defect in chromosomally normal pregnancies. The practical implications of our findings are that patients with unexplained elevations of nuchal translucency may need referral for a fetal echocardiogram.

Infant with severe penicillamine embryopathy born to a woman with Wilson disease

We report a chromosomally normal infant boy with congenital diffuse cutis laxa, severe micrognathia, contractures of all limbs, and central nervous system abnormalities including agenesis of the corpus callosum, born to a woman taking D-penicillamine (DP) for Wilson disease (WD) throughout her pregnancy. His postnatal course was remarkable for chronic lung disease, profound developmental delays, and probable cortical blindness, as well as resolution of his cutis laxa. Embryopathy is a rare complication in babies born to pregnant women treated with DP, and there have been only seven previous reports of birth defects in exposed infants (three of which had favorable postnatal outcomes). The etiology of the severe outcome in this boy is unclear, but prenatal measurement of maternal copper and zinc levels may be indicated for management.

Sequential Pathways of Testing After First-Trimester Screening for Trisomy 21

OBJECTIVE

To evaluate the performance and use of second-trimester multiple-marker maternal serum screening for trisomy 21 by women who had previously undergone first-trimester combined screening (nuchal translucency, pregnancy-associated plasma protein A, and free beta-hCG), with disclosure of risk estimates.

METHODS

In a multicenter, first-trimester screening study sponsored by the National Institute of Child Health and Human Development, multiple-marker maternal serum screening with alpha-fetoprotein, unconjugated estriol, and total hCG was performed in 4,145 (7 with trisomy 21) of 7,392 (9 with trisomy 21) women who were first-trimester screen-negative and 180 (7 with trisomy 21) of 813 (52 with trisomy 21) who were first-trimester screen-positive. Second-trimester risks were calculated using multiples of the median and a standardized risk algorithm with a cutoff risk of 1:270.

RESULTS

Among the first-trimester screen-negative cohort, 6 of 7 (86%) trisomy 21 cases were detected by second-trimester multiple-marker maternal serum screening with a false-positive rate of 8.9%. Among the first-trimester screen-positive cohort, all 7 trisomy 21 cases were also detected in the second trimester, albeit with a 38.7% false-positive rate.

CONCLUSION

Our data demonstrate that a sequential screening program that provides patients with first-trimester results and offers the option for early invasive testing or additional serum screening in the second trimester can detect 98% of trisomy 21-affected pregnancies. However, such an approach will result in 17% of patients being considered at risk and, hence, potentially having an invasive test.

LEVEL OF EVIDENCE

II-2

Association of extreme first-trimester free human chorionic gonadotropin-beta, pregnancy-associated plasma protein A, and nuchal translucency with intrauterine growth restriction and other adverse pregnancy outcomes

OBJECTIVE

The purpose of this study was to determine the association between first-trimester trisomy 21 screening markers (free human chorionic gonadotropin-beta [hCG], pregnancy-associated plasma protein A [PAPP-A], and nuchal translucency) and adverse pregnancy outcome.

STUDY DESIGN

This was a cohort study of 8012 patients enrolled in a National Institute of Child Health and Human Development-sponsored study of first-trimester trisomy 21 and 18 screening. Trisomy 21 and 18 risk results and individual marker levels in unaffected pregnancies and pregnancies with adverse outcomes were evaluated.

RESULTS

PAPP-A <1st percentile (OR 5.4, 95% CI 2.8-10.3) and PAPP-A <5th percentile (OR 2.7, 95% CI 1.9-3.9) and free beta-hCG <1st percentile (OR 2.7, 95% CI 1.3-5.9) were associated with increased risk of intrauterine growth restriction (IUGR) with positive predictive values of 24.1%, 14.1%, and 14.3%, respectively. PAPP-A <5th percentile (OR 2.3 95% CI 1.1-4.7) and nuchal translucency >99th percentile (OR 3.5, 95% CI 1.1-11.3) were associated with increased risk of preterm delivery before 34 weeks. Increased risk at screening for trisomy 21 and 18 identified 16 of the 29 other chromosomal abnormalities (55%). Low free beta-hCG, low PAPP-A, and increased nuchal translucency were all associated with an increased rate of fetal abnormality.

CONCLUSION

Extreme values of first-trimester free beta-hCG, PAPP-A, and nuchal translucency are all associated with adverse outcomes. The especially high predictive value for IUGR of PAPP-A levels below the 1st percentile suggests that patients within this group may benefit from increased surveillance for this condition.

Association of Undetectable Unconjugated Estriol on Multiple Marker Screening with Steroid Sulfatase Deficiency

OBJECTIVE

To determine whether all patients with undetectable unconjugated estriol (uE3) on multiple marker screening (MMS) are carriers for steroid sulfatase (STS) deficiency.

METHODS

This is a retrospective review of 65 pregnancies with undetectable uE3 on MMS.

RESULTS

Of the 65 pregnancies, there were 21 that continued, 40 spontaneous losses, 2 lost to follow-up and 2 elective terminations. Of the 21 continuing pregnancies, 15 were determined to be carriers of the STS deletion. Twenty-seven of the 40 pregnancy losses were associated with elevated alpha-fetoprotein (AFP); about half of the losses were shown to have occurred prior to sampling.

CONCLUSION

Patients with undetectable uE3 are likely to be carriers of the STS deletion, except those with associated elevated AFP. Elevated AFP with undetectable uE3 on MMS is a marker of preexisting or impending fetal demise.

The clinical use of karyotyping spontaneous abortions

OBJECTIVE

The objective of this study was to assess the clinical use of routinely karyotyping spontaneous abortion material.

STUDY DESIGN

We retrospectively reviewed the records of the Pittsburgh Cytogenetics Laboratory from January 1, 1998, to December 31, 2001, for all tissues from spontaneous losses at 20 weeks' gestation or less for which complete medical records were available.

RESULTS

There were 517 submitted samples of which 28 (5.4%) failed to grow in culture. Overall, 55.8% of samples were abnormal; 52.3% of normal results were male. In samples from pregnancies at 13 weeks or less the rate of abnormality was 69.1%. When analyzed by maternal age, the rate of abnormality for first-trimester losses was 57.2% in women younger than 35 years, and 82.3% in those 35 years or older. There was no difference in the rate of abnormality when comparing first loss with two or more losses, first pregnancy with two or more pregnancies, or the presence or absence of at least one live birth.

CONCLUSION

Chromosome abnormalities are the cause for pregnancy loss in 50% to 80% of cases, depending on maternal age and gestational age at time of the loss. Karyotyping of spontaneous losses in the first trimester beginning with the patient's second loss provides clinically important etiologic information and decreases the number of evaluations necessary for recurrent pregnancy loss.

First-trimester screening for trisomies 21 and 18

BACKGROUND

Screening for aneuploid pregnancies is routinely performed after 15 weeks of gestation and has a sensitivity of approximately 65 percent, with a false positive rate of 5 percent. First-trimester markers of aneuploidy have been developed, but their use in combination has not been adequately evaluated in clinical practice.

METHODS

We conducted a multicenter study of screening for trisomies 21 and 18 among patients with pregnancies between 74 and 97 days of gestation, based on maternal age, maternal levels of free beta human chorionic gonadotropin and pregnancy-associated plasma protein A, and ultrasonographic measurement of fetal nuchal translucency. A screening result was considered to be positive for trisomy 21 if the calculated risk was at least 1 in 270 pregnancies and positive for trisomy 18 if the risk was at least 1 in 150.

RESULTS

Screening was completed in 8514 patients with singleton pregnancies. This approach to screening identified 85.2 percent of the 61 cases of Down's syndrome (95 percent confidence interval, 73.8 to 93.0), with a false positive rate of 9.4 percent (95 percent confidence interval, 8.8 to 10.1). At a false positive rate of 5 percent, the detection rate was 78.7 percent (95 percent confidence interval, 66.3 to 88.1). Screening identified 90.9 percent of the 11 cases of trisomy 18 (95 percent confidence interval, 58.7 to 99.8), with a 2 percent false positive rate. Among women 35 years of age or older, screening identified 89.8 percent of fetuses with trisomy 21, with a false positive rate of 15.2 percent, and 100 percent of fetuses with trisomy 18.

CONCLUSIONS

First-trimester screening for trisomies 21 and 18 on the basis of maternal age, maternal levels of free beta human chorionic gonadotropin and pregnancy-associated plasma protein A, and measurement of fetal nuchal translucency has good sensitivity at an acceptable false positive rate.

Three cases of tetrasomy 9p

We report three cases of tetrasomy 9p, two of which were confirmed prenatally. All three had characteristic findings on ultrasound and at birth. We also present a review of the literature, which suggests that a recognizable phenotype for this condition is emerging. Common findings on prenatal ultrasound include intrauterine growth restriction, ventriculomegaly, cleft lip or palate, and renal anomalies. These findings can provide a clue toward the prenatal diagnosis of this condition. There is also a clearly recognizable phenotype at birth. Facial characteristics include hypertelorism, broad nasal bridge/bulbous or beaked nose, cleft lip/palate, ear anomalies, and micrognathia. The exact extent of the isochromosome does not seem to predict severity, but mosaic cases are less severe, or at least have a greater probability of survival.

First-trimester trisomy screening: nuchal translucency measurement training and quality assurance to correct and unify technique

OBJECTIVE

To describe the process of training for measuring nuchal translucency at five clinical centers in North America and to evaluate methods of quality assurance and feedback.

DESIGN

Throughout a period of 18 months, the performance of sonographers in measuring fetal nuchal translucency was monitored using qualitative and quantitative methods of review. After 12 months, different approaches (written and personal feedback) were used to inform sonographers of technical aspects that needed to or could be improved.

RESULTS

On initial qualitative review, discrepancies in judgment from different reviewers coincided with suboptimal magnification, failure to visualize the amniotic membrane and/or use of cross-shaped calipers. At subsequent global review, 13 (29%) images of nuchal translucency measurements were considered unacceptable. Quantitative assessment revealed that, during the first part of the study, the means from four sonographers were significantly smaller and the mean from the fifth sonographer was significantly larger than expected on the basis of findings from The Fetal Medicine Foundation (P < 0.0001). Following feedback, sonographers who underestimated nuchal translucency and who received a written report only did not change measurements overall (P = 0.9759). In contrast, those who received additional intervention showed a marked difference (P < 0.0001).

CONCLUSIONS

Global qualitative review of images from one sonographer may be preferable to assessment of individual aspects of images. Results from global qualitative review correspond well with findings from quantitative analysis, indicating that the latter can be applied for ongoing audit. Observation of divergent results should prompt extensive personal feedback, rather than a written report, to prevent sonographers from settling in their own, inappropriate technique.

A novel X chromosome-linked genetic cause of recurrent spontaneous abortion

OBJECTIVE

Unexplained recurrent spontaneous abortion is a common women's health problem that affects approximately 1 of every 200 women who wish to have children. It has long been assumed that a large proportion of recurrent spontaneous abortion results from genetic problems, but no causative genes have been identified to date. Here, we tested the hypothesis that a subset of women with recurrent spontaneous abortion are carriers of X-linked recessive disorders that result in the loss of male pregnancies.

STUDY DESIGN

X chromosome inactivation patterns, an assay used to detect women who are likely to be carriers of X-linked recessive cell-lethal traits, were compared between 105 female patients with idiopathic recurrent pregnancy loss and 101 women (control subjects) with a single successful pregnancy and no history of pregnancy loss. Inheritance patterns and gender of offspring were studied in relevant subsets of participants.

RESULTS

Female patients showed a highly statistically significant increase in the frequency of skewed X chromosome inactivation (90%; P < .0005). Female patients with highly skewed X chromosome inactivation showed a significant decrease in male children. Four of 6 families that were studied showed maternal inheritance of the skewed inactivation trait.

CONCLUSION

We found the 14% of women with unexplained recurrent pregnancy loss show highly skewed X inactivation, which suggests that they are carriers of X-linked recessive lethal traits. Furthermore, the observed gender bias among women with highly skewed X inactivation suggests selective loss of male conceptions, which is consistent with an X chromosome-linked genetic defect that leads to cell death or growth disadvantage. Identification of such female carriers is important for the reproductive counseling and treatment of these women.

Maternal serum screening for fetal trisomy 18: benefits of patient-specific risk protocol

OBJECTIVE

Our goal was to evaluate the effectiveness of two approaches to screen pregnancies for trisomy 18.

STUDY DESIGN

We analyzed the outcome of all pregnancies that were screen positive for trisomy 18 by multiple marker screening (alpha-fetoprotein, unconjugated estriol, and human chorionic gonadotropin) from May 1993 to June 1998. We compared the results of a fixed cutoff protocol to a protocol that incorporates maternal age to generate a patient-specific risk figure.

RESULTS

A total of 45,145 patients were screened. By using the fixed cutoff protocol, 113 patients (0.25%) were screen positive. The risk-based approach was associated with a 0.55% screen-positive rate (250 patients). Eight of 12 cases (67% detection rate) of trisomy 18 were identified by using the risk method, and only 5 cases (42% detection rate) were detected by using the fixed cutoff method. By using the risk-based protocol, 21 pregnancies with chromosomal abnormalities (8, trisomy 18; 7, triploidy; 5, trisomy 21; and 1, mosaic 45X/46XX) were detected. Subsequent fetal death occurred for 42 patients whose fetuses were chromosomally normal and without structural malformations.

CONCLUSION

The patient-specific risk protocol to screen for trisomy 18 is a beneficial adjunct to screening programs already in place for Down syndrome and neural tube defects. Patients found to be screen positive for trisomy 18 are at significant risk for adverse pregnancy outcome.

X chromosome defects as an etiology of recurrent spontaneous abortion

Recurrent spontaneous abortion is a significant problem in women's health, yet it remains a poorly understood phenomenon. Many cases of recurrent spontaneous abortion defy diagnosis, and we predict that a subset of these unexplained cases are caused by previously unknown, recessively inherited genetic causes. Here, we provide background on known genetic factors that contribute to spontaneous abortion and describe a novel X chromosome-based genetic mechanism that may be an important cause of recurrent spontaneous abortion. Recessively inherited defects on the human X chromosome would cause no symptoms in carrier females but would be lethal in utero to male conceptions that receive the defective X. Through investigation of the basic biology of the X chromosome, we propose that the female carriers of such traits can be identified through the molecular finding of skewed X chromosome inactivation. Furthermore, we have observed an association between skewed X chromosome inactivation and recurrent pregnancy loss, supporting the hypothesis that X chromosome defects may be an important, previously unknown cause of recurrent pregnancy loss.

Second-trimester levels of maternal serum human chorionic gonadotropin and inhibin a as predictors of preeclampsia in the third trimester of pregnancy

OBJECTIVE

To determine whether second-trimester maternal serum levels of inhibin A, human chorionic gonadotropin (hCG), unconjugated estriol (uE3), and alpha-fetoprotein (AFP) are predictive of the later onset of preeclampsia in pregnancy.

METHODS

Retrospective evaluation of serum analyte levels in 60 women with preeclampsia compared with 300 controls. Levels of each analyte were compared in women with preeclampsia and controls using matched rank analysis. Analytes that were significantly different between groups were examined with univariate and bivariate Gaussian distribution analysis.

RESULTS

Second-trimester inhibin A (1.36 multiples of the median [MoM]) and hCG (1.40 MoM) levels were significantly but modestly elevated in women who later developed preeclampsia. A combination test of maternal age plus inhibin A and hCG predicted 23% of cases of preeclampsia with 95% specificity. There was a statistically significant trend for inhibin A, but not hCG, levels to be higher when the onset of preeclampsia occurred within a shorter (<17 weeks) interval after collection of the second-trimester screening sample.

CONCLUSIONS

Second-trimester serum levels of inhibin A and hCG are modest predictors of the later onset of preeclampsia. Inhibin A may be a better predictor of early-onset preeclampsia, which is associated with a higher maternal and perinatal morbidity and mortality, than preeclampsia at or near term.

Insights into the pathogenesis and natural history of fetuses with multicystic dysplastic kidney disease

To better delineate the natural history of multicystic displastic kidney disease (MCDKD) and provide insights into the pathogenesis of this condition, we report our experience in 102 prenatally detected cases. MCDKD is most commonly an incidental finding on prenatal ultrasound examination. The abnormality may be unilateral (76 per cent) or bilateral (24 per cent). In unilateral cases, abnormality of the contralateral kidney is common (33 per cent). Associated non-renal abnormalities occur frequently with both unilateral (26 per cent) and bilateral (67 per cent) MCDKD, and increase the risk for an abnormal chromosome study. Males are more likely to be affected than females with a ratio of 2.4:1, but females are twice as likely to have bilateral MCDKD and associated non-renal abnormalities, and four times more likely to have an abnormal chromosome study. We suggest that the option of chromosomal analysis should be discussed with all patients diagnosed with MCDKD in their fetus, if there is bilateral renal involvement or if an associated non-renal abnormality is present. Unilateral MCDKD without associated renal or non-renal abnormalities was not associated with an abnormal chromosome study, and resulted in favourable outcomes. While unilateral MCDKD, lack of associated anomalies, normal chromosome study and adequate amniotic fluid are all reassuring findings, a complete neonatal urologic work-up should be performed in all newborns. We believe the evaluation should include voiding cystourethrography to rule out vesicoureteral reflux. Our findings allow more precise counselling of patients regarding prognosis, and subsequent management of the fetus found to have MCDKD.

The use of interphase FISH for prenatal diagnosis of Pallister-Killian syndrome

Pallister-Killian syndrome (tetrasomy 12p) is a relatively rare aneuploidy syndrome characterized by the presence of mosaicism for an isochromosome 12p [i(12p)]. We report two new cases diagnosed following chorionic villus sampling and an abnormal ultrasound, respectively. Fluorescent in situ hybridization (FISH) was used to enumerate the number of interphase cells containing the isochromosome. The results of these studies illustrate the importance of the use of interphase FISH to detect the presence of the i(12p) in uncultured, non-dividing cells. A review of the literature identified 23 additional cases of Pallister-Killian syndrome diagnosed prenatally. Approximately 50 per cent of these cases were associated with the presence of a congenital diaphragmatic hernia. We suggest that a perinatal-lethal form of Pallister-Killian syndrome is underdiagnosed and recommend that all cases of prenatally detected diaphragmatic hernia be tested for Pallister-Killian syndrome using interphase FISH on uncultured amniocytes.

Choroid plexus cysts and trisomy 18: risk modification based on maternal age and multiple-marker screening

Choroid plexus cysts are more common in fetuses with chromosomal aneuploidies, particularly trisomy 18. Although it is accepted that the risk of karyotypic abnormality justifies amniocentesis when associated abnormalities are present, disagreement continues as to the risk of trisomy 18 in a fetus with an isolated choroid plexus cyst. We propose consideration of maternal age and multiple-marker screening for chromosomal aneuploidy in the assessment of risk. Bayesian statistical modeling was used to calculate the risk of trisomy 18 from age-related risk figures for trisomy 18 and the incidence of isolated choroid plexus cysts in fetuses with trisomy 18. The risk was further modified on the basis of the ability of multiple-marker screening to detect fetuses with trisomy 18. From risk estimates calculated across maternal ages 20 to 45 years, the risk of trisomy 18 does not approach that of amniocentesis until a maternal age of > or = 37 years. Therefore in the presence of an isolated choroid plexus cyst and normal multiple-marker screen results amniocentesis is justified only in the patient with advanced maternal age.

Preconception genetic counseling

The purpose of this chapter has not been to be all-inclusive, but to raise awareness of the benefits of preconception consultation in the prevention of birth defects. If there is to be a significant decrease in the incidence of congenital malformations, it will come only by intervention that occurs prior to organogenesis, and that opportunity is lost by the first prenatal visit. For the practitioner interested in a more in-depth analysis of the subject of preconception counseling, the two books listed as supplementary reading provide a wealth of information essential to the care of the patient planning a pregnancy.

45,X/46,XY mosaicism: the role of ultrasound in prenatal diagnosis and counselling

The purpose of this study was to assess the benefit of ultrasound evaluation for fetuses with prenatally diagnosed 45,X/46,XY mosaicism. The charts of all patients who underwent chorionic villus sampling and/or amniocentesis between 1 March 1990 and 31 October 1995 were screened for 45,X/46,XY mosaicism. Cases were divided on the basis of the results of the confirmatory amniocentesis into two groups: (1) confined placental mosaicism (n = 4); and (2) true fetal 45,X/46,XY mosaicism (n = 4). All patients underwent high-resolution detailed ultrasound study between 16 and 22 weeks. If the initial ultrasound study failed to visualize fetal genitalia, scanning was repeated in 2 weeks. Chromosome analysis was carried out on the newborn's skin to confirm the prenatal result. Six cases were found to have 45,X/46,XY mosaicism on chorionic villus sampling. Amniocentesis indicated a normal 46,XY male karyotype for three fetuses and true fetal 45,X/46,XY mosaicism for two cases. One patient declined follow-up amniocentesis. At birth, this newborn was documented to have normal male genitalia and a 46,XY karyotype. An additional two cases underwent amniocentesis only and were documented to have 45,X/46,XY mosaicism. High-resolution detailed ultrasound study between 16 and 22 weeks revealed seven fetuses with normal male genitalia and one fetus with ambiguous genitalia. Of the four neonates with true 45,X/46,XY mosaicism this was the only one found to have ambiguous genitalia. We conclude that the work-up of patients with 45,X/46,XY mosaicism should include ultrasound study to look for ambiguous genitalia. This allows appropriate counselling regarding the natural history of the condition and aids in the planning for management in the postnatal period.

Molecular cytogenetics: an essential component of modern prenatal diagnosis

Traditional cytogenetic studies with high-resolution banding techniques have been the mainstay of prenatal diagnosis for > 20 years. However, this approach is limited by the resolution of light microscopy, and it requires cultured cells, necessitating a significant delay in obtaining chromosome studies. The advent of molecular cytogenetics, or fluorescence in situ hybridization, has added an adjunctive tool to overcome both these limitations. During a 16-month period 35 prenatal diagnosis cases had molecular cytogenetic studies performed; 71% of the evaluations were informative. We present five of these cases to illustrate the benefits of this technique for clinical prenatal diagnosis.

Early prenatal diagnosis of an infratentorial arachnoid cyst: association with an unbalanced translocation

Arachnoid cysts are an uncommon central nervous system malformation, representing only 1 per cent of all intracranial masses. We report the second-trimester prenatal diagnosis of a posterior fossa arachnoid cyst, associated with an unbalanced X;9 translocation.

Determination of normal human fetal immunoglobulin M levels

Immunoglobulin M (IgM) levels were measured in 198 cord blood samples from 192 apparently normal pregnancies from 24 weeks of gestation to term. Simple linear regression analysis yielded a standard curve for IgM development during pregnancy showing a 0.5 mg/dl increase in IgM per week of gestation. This curve allows the comparison of fetal IgM levels from pregnancies considered to be at risk for intrauterine infection.

Osteogenesis imperfecta and campomelic dysplasia: difficulties in prenatal diagnosis

The classic features of osteogenesis imperfecta and campomelic dysplasia typically are so specific that these two forms of skeletal dysplasia are among the few that can be diagnosed in the second trimester of pregnancy. We report a series of seven examples of osteogenesis imperfecta and one example of campomelic dwarfism to illustrate the difficulty of differentiating these two disorders in utero. The prenatal sonographic findings in three of the osteogenesis imperfecta cases mimicked campomelic dwarfism, whereas the case of campomelic dwarfism was antenatally diagnosed as osteogenesis imperfecta.

Gorlin syndrome (naevoid basal cell carcinoma syndrome): prenatal detection in a fetus with macrocephaly and ventriculomegaly

The Gorlin (naevoid basal cell carcinoma) syndrome is an autosomal dominant disorder consisting principally of naevoid basal cell carcinomas, odontogenic keratocysts, skeletal abnormalities, and intracranial calcification. We report the prenatal detection of the Gorlin syndrome by ultrasonography in a fetus with macrocephaly and mild ventriculomegaly.

Desbuquois syndrome: clinical, radiographic, and morphologic characterization

To further characterize the clinical, radiographic and chondro-osseous morphologic changes in the Desbuquois syndrome, 7 patients from three sibships are described. They all had prenatal onset severe rhizomelic and mesomelic shortness with marked joint laxity and marked micrognathia. Radiographic changes were distinct, consisting of a supernumerary ossification center between the proximal phalanx of the index finger and the second metacarpal, and variable thumb changes. The femoral necks showed enlargement of the lesser trochanter with metaphyseal breaking, producing a characteristic "monkey wrench" (Swedish key) appearance. Growth plate cartilage showed dilated cisterns of rough endoplasmic reticulum in reserve zone chondrocytes. Three of the 7 cases were diagnosed prenatally by second trimester ultrasound and one case by fetoscopy. This syndrome exhibits significant phenotypic variability and must be differentiated from the Catel-Manzke syndrome which exhibits similar radiographic changes in the hands.

Antenatal diagnosis of fetal pelvic kidneys

OBJECTIVE

To review our experience with the antenatal detection and subsequent neonatal outcome of fetuses with a pelvic kidney.

METHODS

A retrospective review of 25,551 obstetric ultrasound examinations performed after 16 weeks' gestation identified 13 cases of fetal pelvic kidneys (one per 1965 examinations).

RESULTS

Three pelvic kidneys were dysplastic; the remainder appeared sonographically normal. Seven pelvic kidneys were measured; five were smaller than expected for gestational age. Associated anomalies were detected in three cases.

CONCLUSIONS

Careful second- and third-trimester ultrasound examinations can detect an absence of the kidney in the renal fossa. Evaluating the migratory path of the kidney from the pelvis to the renal fossa will frequently result in detection of an ectopic kidney.

Increased echogenicity in the fetal abdomen: use of DNA analysis to establish a diagnosis of cystic fibrosis

The sonographic finding of increased echogenicity within the fetal abdomen presents a diagnostic dilemma, with a differential diagnosis ranging from normal variation to CF. We report the diagnostic evaluation of four cases, two of which were found to be the result of CF. On the basis of this experience, we believe that persistence of an echogenic bowel pattern, especially with bowel dilation, after 20 weeks' gestation should prompt an evaluation for CF. Using DNA analysis, approximately 75% of the cases involving CF can be detected with noninvasive studies of the parents, and confirmation by amniocentesis is performed only in those cases in which both parents are carriers of known mutations.

Intraamniotic 15(s)-15-methyl prostaglandin F2 alpha and termination of middle and late second-trimester pregnancy for genetic indications: a contemporary approach

OBJECTIVE

Our purpose was to determine whether intraamniotic 15(s)-15-methyl prostaglandin F2 alpha could serve effectively and safely as a surrogate for natural prostaglandin F2 alpha when used to effect middle and late second-trimester pregnancy termination for genetic indications. Further, we sought to compare efficacy and side effects with those found when intravaginal prostaglandin E2 is used.

STUDY DESIGN

A total of 62 patients received intraamniotic 15(s)-15-methyl prostaglandin F2 alpha and urea, and intracervical laminaria. Case patients at < or = 20 weeks' gestation (n = 32) were compared with case patients at > 20 weeks (n = 30) and with a matched group (n = 64; 1:2 ratio) of control patients in whom cervical laminaria and intraamniotic urea were used with prostaglandin E2 vaginal suppositories.

RESULTS

The mean induction-to-abortion interval among the case patients (gestational age 16 to 27 weeks) was 13 hours 11 minutes; 60 of 62 (97%) were delivered within 24 hours. There was a statistically significant negative correlation between the induction-to-abortion interval and gestational age (p = 0.04). When patients at < or = 20 weeks and those at > 20 weeks were compared, few differences were noted. The mean induction-to-abortion interval for case patients at < or = 20 weeks was 13 hours 54 minutes versus 19 hours 34 minutes for control patients (p = 0.001). One of 32 (3%) case patients remained undelivered beyond 24 hours compared with 17 of 64 (27%) control patients (p < 0.01). Immediate and delayed complications were uncommon in either group.

CONCLUSION

Our study demonstrates that 15(s)-15-methyl prostaglandin F2 alpha can serve safely as a surrogate for prostaglandin F2 alpha when used in combination with urea and laminaria for termination of pregnancy. This technique appears safe for use through 27 weeks' gestation; further investigation is encouraged.

Prenatal diagnosis of cytomegalovirus (CMV) infection: a preliminary report

Eight patients were referred for prenatal diagnosis for suspected fetal cytomegalovirus infection (CMV): six for documented first-trimester infection and two for abnormal ultrasound evaluation suggestive of fetal infection. Three methods of diagnosis were employed: (1) amniotic fluid viral cultures and CMV-specific IgM in fetal serum; (2) amniotic fluid cultures and detection by polymerase chain reaction amplification of CMV-specific DNA in chorionic villi; and (3) detection of CMV-specific DNA in villus samples only. Amniotic fluid cultures detected all cases of infection, but CMV-specific IgM was not a reliable indicator of infection in any case. DNA analysis correlated well with both culture results and clinical outcome.

Congenital nephrosis: detection of index cases through maternal serum alpha-fetoprotein screening

Congenital nephrosis is an autosomal recessive disorder with an incidence of 1 in 8000 in Finland, but it is quite rare in non-Finnish populations. In families known to be at risk, prenatal detection is possible by means of maternal serum and/or amniotic fluid alpha-fetoprotein levels. We report the antenatal diagnosis of four cases of congenital nephrosis, three of which were index cases, through maternal serum alpha-fetoprotein screening. The diagnosis was confirmed at birth in two infants. Two patients elected to terminate their pregnancies, and the diagnoses were confirmed pathologically (obliteration of foot processes on electron microscopy of fetal glomeruli) in both. In cases of elevated maternal serum alpha-fetoprotein, with unexplained and marked elevations of amniotic fluid alpha-fetoprotein and normal acetylcholinesterase levels, the diagnosis of congenital nephrosis must be considered regardless of ethnic origin.

Chorionic villus sampling: the University of Maryland experience

The University of Maryland was the first program in the state to offer chorionic villus sampling (CVS). Since the program's beginning in 1984, 998 patients have been seen with successful sampling in 99.1 percent, using both transcervical and transabdominal approaches. The overall loss rate was quite low (2.3 percent), and no increased risk of birth defects was seen. These observations demonstrate that CVS provides a safe and accurate alternative to amniocentesis.