The impact of MSAFP screening on genetic services, 1984–1986

The impact of maternal serum alpha-fetoprotein (MSAFP) screening on genetic centers was investigated by a questionnaire mailed to 220 genetic centers in the United States. Eighty-four (38%) of centers responded to the questionnaire; of these (34%) were adequate for analysis. About 33% of the programs performed their own MSAFP testing. Approximately 70% of centers used 2.5 times the median (MoM) as a cutoff for MSAFP elevations and approximately 75% of centers used a sliding cutoff for low MSAFP based on both maternal age and the multiple of the median. Between 1984 and 1986, the total number of women screened by the reporting centers increased by about 4.7 fold. The percentage of women seen in their centers for prenatal counseling due to high or low MSAFP levels increased from 1.3% in 1984 to 13.1% in 1986. The percentage of prenatal diagnoses utilizing amniocentesis for high or low MSAFP increased from 3% in 1984 to 10% in 1986. During this period, 76 cases of Down syndrome were detected based on low MSAFP; this represents 1.7% of amniocenteses for low MSAFP. These data demonstrate a significant increase in the number of women seen for prenatal counseling and amniocentesis at the reporting genetic centers and is likely to represent a similar trend at all genetic centers. The impact of high MSAFP screeing for neural tube defects and low MSAFP screening for Down syndrome is likely to increase over the coming years and genetic programs should prepare for the increasing utilization of services necessary to handle women with high and low MSAFP levels.     

Parity and Down syndrome

Previous studies have suggested a positive correlation between grand multiparity and the incidence of Down syndrome (DS). In order to study different parities as risk factors for DS, the Swedish health registries were used, and 2,615 infants with Down syndrome were selected from 2,184,590 infants born in 1973–1993. A statistically significant risk decrease for primiparas, and a significant risk increase for grand multiparas (5+), was found (age-adjusted odds ratios: 0.87 (95% CI: 0.80–0.96) and 1.40 (95% CI: 1.18–1.65)), respectively. Potential confounders, such as the effect of truncated maternal 1-year age classes, citizenship, socioeconomic level, etc., were evaluated but were found to have only marginal effects. Evidence suggesting that the extension of prenatal diagnosis during the study period has decreased the incidence of DS among women of parity 1–4, but not among women of parity 5+, was found. The hypothesis that Swedish grand multiparas may have another attitude toward prenatal diagnosis than women of lower parities was confirmed when, in a data set containing information on 872 amniocenteses, a significantly lower rate of grand multiparity than expected was found. For the negative association between primiparity and DS, no obvious confounder was found. Am. J. Med. Genet. 70:196–201, 1997. © 1997 Wiley-Liss, Inc.     

Prenatal diagnosis of fragile X syndrome and the risk of expansion of a premutation

The aim of the present study was to evaluate prospectively the dynamics of the FMR1 gene. The risk of full mutation among pregnant women and the carriers, and the risk of expansion of a premutation allele to a full mutation were estimated. We identified 89 pregnant women with an expanded FMR1 gene seeking prenatal diagnosis. Amniocentesis or chorion villus sampling (CVS) was offered and a DNA test of the FMR1 gene was carried out in such pregnancies. The overall risk of full mutation among women (N = 21) with a repeat size between 60 and 80 was 4.8% (one fetus with mosaicism), and the risk of expansion of the premutation allele to a full mutation was 14% in those offspring to whom the premutation allele was transmitted. The risk of full mutation among the carriers (N = 13) with a repeat size between 81 and 100 was 61.5% (8/13), and the risk of expansion of a premutation allele to a full mutation was 89%. Only one case fell into the category of 101-200 repeats, and expansion to a full mutation was recorded. Fetuses of full mutation mothers inherited the larger allele in 64% (14/22) of the cases. The range of 40-59 repeats was safe: there were no fetal full mutations. The risk of full mutation was also low among the subjects with a repeat size between 60 and 80, whereas the risk increased significantly after 80 repeats. Maternal premutation size was positively correlated with the risk of having a full mutation offspring.     

Psychological aspects of amniocentesis: anxiety feelings in three different risk groups

A review of the literature about parents' experiences with amniocentesis is given in the first part of this paper. In the second part the results of a follow-up study in Belgium are presented. Three groups of women who had amniocentesis performed because of advanced maternal age, a previous child with Down syndrome or a previous child with neural tube defect, respectively, were interviewed at home about their experiences. Anxiety feelings were different between groups but also showed considerable variation within each group. The overall psychological evaluation of the procedure was positive, so that the majority of the women would opt for amniocentesis in a subsequent pregnancy and would recommend it to others. Later follow-up contact by mailed questionnaire revealed that almost all women elected for their subsequent pregnancies to be monitored by amniocentesis.     

The centralized prenatal genetics screening program of New York City: I. Developmental phase

The increasing demand in New York City for prenatal diagnosis of genetic disorders has necessitated the development of a large-scale, centralized prenatal genetic screening program. The objective of this program is eventually to serve 3,000 to 4,000 at-risk New York City pregnant women annually. Through the teamwork of a task force comprising representatives from the New York Scientists' Committee for Public Information (SCPI), the Medical and Health Research Association of New York City, Inc. (MHRA), the New York State and New York City Departments of Health, and five different advisory committees, the centralized Prenatal Diagnosis Laboratory of New York City (PDL) was designed and established. While this program aims to provide high quality, centralized laboratory service for the prenatal detection of chromosome abnormalities and open neural tube defects, it also emphasizes quality-controlled services in genetic counseling, amniocentesis, ultrasound monitoring, obstetric care, and patient follow-up. Genetic counseling by PDL-employed counselors is made available to patients whenever the participating hospital lacks such service or cannot handle their patient load. In addition, PDL has launched a vigorous public health education program. A detailed guideline for the program was prepared describing the highest standards of quality for each component. The initial step was the developmental phase that included establishing the advisory committees, searching for sponsors, preparing guidelines, developing the health education program, renovating the laboratory site, purchasing and installing equipment, and recruiting of staff. The experience gained from this endeavor will be value in the development of similar large-scale prenatal diagnosis programs.     

无创产前筛查技术在产前筛查与诊断技术体系中的效能分析

目的:评价无创产前检测(non-invasive prenatal testing,NIPT)技术在产前筛查中的效能及其在产前诊断体系中的作用。方法:对22 649例单胎孕妇的产前筛查结果及诊断路径进行效能分析。对同期接受介入性产前诊断的9268例本院和转诊孕妇的指征及结局进行效能分析。结果:孕妇选择唐筛比例为60.2...     

Familial congenital diaphragmatic hernia: Prenatal diagnostic approach and analysis of twelve families

Congenital diaphragmatic hernia is generally recognized as a sporadic malformation with little or no risk of recurrence. A family with three affected individuals in two generations is presented. In addition, new prenatal diagnostic techniques including ultrasonography and amniography are discussed. A comparison of associated physical characteristics in isolated versus twelve familial cases of diaphragmatic hernia is presented. In the familial group, there was a higher incidence of affected males (M:F ratio = 2.1 versus 0.67), a higher incidence of bilateral defects (20% versus 3%) and a lower incidence of additional life-threatening malforamtions 3.6% versus 47%). Analysis of available pedigree data favors multifactorial inheritance with a high male: female sex ratio as the most probable mode of transmission.     

早孕期唐氏综合征联合筛查高风险对象的妊娠结局分析

目的对2008-2009年我院早孕期唐氏联合筛查的妊娠对象出生后妊娠结局进行回顾性随访。方法 2008-2009年,我院完成单胎妊娠早孕期唐氏联合筛查共计5218例。对所有病例全部进行随访,随访方式主要以病案追踪及电话随访为主。随访内容主要包括胎儿宫内发育情况及新生儿出生后健康状况。采用切割值1/250,对阳性筛查对象与阴性筛查对象的妊娠结局进行比较分析。结果 5218例筛查对象中,151例(2.9%)孕妇筛查阳性,127例(84.1%)成功随访。127例阳性筛查对象与3700例阴性筛查对象进行比较,阳性对象存在显著的不良妊娠结局高风险(不良妊娠结局16.5%vs 1.6%,P<0.001;染色体异常8.7%vs 0.1%,P<0.001;结构畸形6.3%vs 0.9%,P<0.001;较早期自然流产1.6%vs 0.1%,P<0.001)。结论筛查阳性妊娠对象,除了存在胎儿染色体异常高风险外,胎儿结构畸形和自然流产的风险亦较高。     

Factors influencing maternal estimates of genetic risk

The relationship between the objective and subjective estimates of genetic risk was studied in 202 women accepting and 50 women not accepting amniocentesis. All women were at risk of having a child with congenital anomalies either because of maternal age at pregnancy or family history of Down syndrome (DS) or other congenital anomalies. Only 28.6% of the women rejecting and 44.4% of the women accepting amniocentesis remembered correctly their objective odds. The correlations between the objective risk estimates and the subjective risk estimates were low overall (r = 0.089, p = 0.08); for women rejecting (r = 0.024, p = 0.44) or accepting (r = 0.082, p = 0.12) amniocentesis. The psychosocial and sociodemographic variables relating to either objective or subjective risk estimates were different for both groups of women. The study provides information on variables that should be taken into consideration in formulating a general theory to predict individual perceptions of genetic risk.     

Maternal serum markers levels in consecutive pregnancies: A possible genetic predisposition to abnormal levels

The study comprised 2,361 women, each with two consecutive normal uncomplicated pregnancies screened at 15–20 weeks gestation for maternal serum alpha-fetoprotein levels (AFP). In 1,816 of these women, maternal serum human chorionic gonadotropin (hCG) levels were tested as well. The proportion of women who had a second high AFP level (≥2.0 MOM) in their subsequent pregnancy was 6.5-fold higher as compared with the proportion of women who had normal levels of AFP in their first tested pregnancy. The relative chance of having a second positive result of a low level of AFP (AFP ≤0.5 MOM) in subsequent pregnancies was 3.8-fold higher. The relative chances of having a second positive result of high or low levels of hCG were 3.9- and 2.2-fold higher, respectively. It is concluded that there is a predisposition for abnormal levels of serum markers that is influenced by genetic and/or environmental factors. Therefore it is suggested that the individual's risk of having a Down syndrome baby, or other adverse pregnancy outcome that is derived from the serum markers' levels, should be adjusted taking into account unexplained high or low levels in previous pregnancies. A screening policy is suggested which is designed to yield a lower false-positive rate without affecting the detection rate of abnormal pregnancies. More data are needed before an accurate adjustment based on previous results can be made. © 1996 Wiley-Liss, Inc.     

Rates of Down syndrome at livebirth by one-year maternal age intervals in studies with apparent close to complete ascertainment in populations of European origin: A proposed revised rate schedule for use in genetic and prenatal screening

Precision and accuracy in determining rates of Down syndrome at livebirth are indispensible to algorithms which determine eligibility for prenatal cytogenetic diagnostic services. We derived Down syndrome rates by single year of maternal age which we propose as a revised rate schedule for background risk. Data on European-origin populations were obtained from 5 sources judged most likely to have complete ascertainment of cases. A “constant plus exponent” regression model and variants extending the analysis to higher powers of maternal age were applied to several ranges of maternal age. Confidence intervals about the rates were calculated. This analysis results in rates significantly higher than those in widespread use though the confidence intervals show a need for caution in assuming precision. Sources of variation in rates are also considered. © 1996 Wiley-Liss, Inc.     

Noninvasive prenatal screening (NIPS) for fetal chromosome abnormalities in a general-risk population: An evidence-based clinical guideline of the American College of Medical Genetics and Genomics (ACMG)

PurposeThis workgroup aimed to develop an evidence-based clinical practice guideline for the use of noninvasive prenatal screening (NIPS) for pregnant individuals at general risk for fetal trisomy 21, trisomy 18, or trisomy 13 and to evaluate the utility of NIPS for other chromosomal disorders.MethodsThe NIPS Evidence-Based Guideline Work Group (n = 7) relied on the results from the recent American College of Medical Genetics and Genomics (ACMG) systematic review to form the evidentiary basis of this guideline. Workgroup members used the Grading of Recommendations Assessment, Development, and Evaluation Evidence to Decision framework to draft recommendations. The guideline underwent extensive internal and external peer review with a public comment period before approval by the ACMG Board of Directors.ResultsEvidence consistently demonstrated improved accuracy of NIPS compared with traditional screening methods for trisomies 21, 18, and 13 in singleton and twin gestations. Identification of rare autosomal trisomies and other microdeletion syndromes with NIPS is an emerging area of interest.ConclusionACMG strongly recommends NIPS over traditional screening methods for all pregnant patients with singleton and twin gestations for fetal trisomies 21, 18, and 13 and strongly recommends NIPS be offered to patients to screen for fetal sex chromosome aneuploidy.     

Assessment of reproductive risk and intentions by mothers of children with hemophilia

Thirty-five mothers of children with hemophilia were studied in order to ascertain the impact of hemophilia on family planning. Attitudes about reproductive risks and prenatal diagnosis were also examined. The most important factors influencing family planning in this group were parental fulfillment and availability of medical care and education for their affected child. Although 79% of mothers viewed their reproductive risk as moderate to very high, 57% indicated that their reproductive plans had not changed even with this knowledge. While 43% of the group would consider prenatal diagnosis, only 17% would terminate a pregnancy if the fetus was found to have hemophilia. Of those interested in prenatal diagnosis, the majority were interested in knowing if the fetus was affected but would not consider termination of the pregnancy. The majority of mothers in the group did not view having a child with hemophilia as an insurmountable burden on their lives. Therefore, the disease appeared to have little impact on family planning.     

Prenatal diagnosis of congenital myotonic dystrophy and counseling of the pregnant mother: Case report and literature review

The molecular basis of the myotonic dystrophy (MD) kinase gene is expansion of the CTG repeat at the 3′-untranslated region of the MD gene. Variability of the CTG repeat size in different tissues of affected individuals has been demonstrated. The objective of this report was to examine and review the feasibility of prenatal diagnosis of congenital myotonic dystrophy (CMD) in pregnant women with MD using CTG repeat sizes in amniocytes or villi. We present a case of a pregnant woman with MD who underwent prenatal diagnosis of MD using amniocytes. The repeat size in the amniocytes was smaller than the repeat size in the maternal leukocytes and smaller than the repeat size in the infant blood. The infant had CMD. We also reviewed the literature for reports on MD cases that were prenatally tested for CTG repeat size using amniocytes or chorionic villi. Data were tabulated based on the number of maternal CTG repeats, prenatal procedure [amniocentesis or chorionic villus sampling (CVS)], CTG repeat size in fetal tissue, fetal/infant blood, and pregnancy outcome. Twenty-seven pregnancies at risk for MD that underwent prenatal diagnosis were reported. Eleven (40.7%) of the 27 pregnancies underwent amniocentesis, and 16 (59.3%) underwent CVS. Fourteen patients (61%) demonstrated an increase in CTG repeat size in the amniocytes or villi compared with the maternal repeat size. Nine (33%) of the 27 pregnancies were terminated because of CMD risk. The outcomes of 11 (40.7%) pregnancies were consistent with diagnosis of CMD. CMD was diagnosed in fetuses demonstrating expansion or contraction of the CTG mutation in the amniocytes. Prenatal diagnosis of MD is possible by using mutation analysis on maternal and fetal DNA and detection of the CTG repeat expansion. Prenatal diagnosis of CMD is more complex. The possible lack of correlation between CTG repeat size in amniocytes, villi, and other fetal tissues is a potential limitation in prenatal diagnosis and counseling of CMD using CTG repeat size. Thus, prenatal diagnosis of CMD should be based on a combination of factors, including maternal pregnancy history, clinical findings, and cautious interpretation of maternal and fetal DNA analysis. Am. J. Med. Genet. 78:250–253, 1998. © 1998 Wiley-Liss, Inc.     

Systematic evidence-based review: The application of noninvasive prenatal screening using cell-free DNA in general-risk pregnancies

PurposeNoninvasive prenatal screening (NIPS) using cell-free DNA has been assimilated into prenatal care. Prior studies examined clinical validity and technical performance in high-risk populations. This systematic evidence review evaluates NIPS performance in a general-risk population.MethodsMedline (PubMed) and Embase were used to identify studies examining detection of Down syndrome (T21), trisomy 18 (T18), trisomy 13 (T13), sex chromosome aneuploidies, rare autosomal trisomies, copy number variants, and maternal conditions, as well as studies assessing the psychological impact of NIPS and the rate of subsequent diagnostic testing. Random-effects meta-analyses were used to calculate pooled estimates of NIPS performance (P < .05). Heterogeneity was investigated through subgroup analyses. Risk of bias was assessed.ResultsA total of 87 studies met inclusion criteria. Diagnostic odds ratios were significant (P < .0001) for T21, T18, and T13 for singleton and twin pregnancies. NIPS was accurate (≥99.78%) in detecting sex chromosome aneuploidies. Performance for rare autosomal trisomies and copy number variants was variable. Use of NIPS reduced diagnostic tests by 31% to 79%. Conclusions regarding psychosocial outcomes could not be drawn owing to lack of data. Identification of maternal conditions was rare.ConclusionNIPS is a highly accurate screening method for T21, T18, and T13 in both singleton and twin pregnancies.     

Preimplantation genetic diagnosis for couples at high risk of Down syndrome pregnancy owing to parental translocation or mosaicism

The population risk for trisomy 21 is 1 in 700 births but some couples are at a much higher risk owing to parental translocation or mosaicism. We report on the first attempt to carry out preimplantation genetic diagnosis for two such couples using cleavage stage embryo biopsy and dual colour FISH analysis. Each couple underwent two treatment cycles. Couple 1 (suspected gonadal mosaicism for trisomy 21) had two embryos normal for chromosome 21 transferred, but no pregnancy resulted; 64% (7/11) unfertilised oocytes/embryos showed chromosome 21 aneuploidy. Couple 2 (46,XX,t(6;21)(q13;q22.3)) had a single embryo transferred resulting in a biochemical pregnancy; 91% (10/11) oocytes/embryos showed chromosome 21 imbalance, most resulting from 3:1 segregation of this translocation at gametogenesis. The opportunity to test embryos before implantation enables the outcome of female meiosis to be studied for the first time and the recurrence risk for a Down syndrome pregnancy to be assessed.


Keywords: preimplantation genetic diagnosis; Down syndrome; reciprocal translocation; gonadal mosaicism     

武汉地区2613例产前筛查高风险孕妇的产前诊断

目的评价羊水细胞染色体分析和产前无创基因检测对诊断胎儿染色体异常的临床应用价值。方法对43284例孕14—20^＋6周的孕妇采用化学发光法进行血清AFP、Free—ISHCG和uE3浓度的检测,结合孕周、体重、年龄等因素,通过风险评估软件进行风险评估。将筛查结果与B超、羊水染色体分析、新生儿检查结果对照。结果43284例孕妇中产前筛查高风险2613例。其中唐氏综合征高风险2178例,筛查阳性率为5．03％（2178／43284）,经产前无创基因检测和羊水染色体核型分析确诊19例唐氏综合征患儿;18-三体高风险者195例筛查阳性率为0．45％（195／43284）,经产前无创基因检测和羊水染色体分析确诊4例;神经管缺陷高危者240例,筛查阳性率为0．55％（240／43284）,经超声检查确诊为神经管缺陷胎儿56例。结论产前筛查和产前诊断可减少缺陷儿的出生,具有明显的经济效益和社会效益,是落实优生优育政策非常有效的技术手段。