Factors limiting the effectiveness of prenatal screening for anencephaly and spina bifida in a high-risk area

Summary. The effectiveness of a prenatal screening programme in reducing the birth prevalence of anencephaly and spina bifida (ASB) is influenced by three principal factors: the proportion of affected pregnancies screened (uptake), the proportion of affected pregnancies detected on screening (sensitivity) and the proportion of affected pregnancies terminated when detected (compliance). The purpose of the study was twofold: to develop an epidemiologically-based method for the retrospective monitoring of these three factors and to attempt to quantify their relative importance in relation to the outcome of screening. Data on births and terminations associated with ASB for the period 1976–1986 were obtained from the Glasgow Register of Congenital Anomalies and from the Department of Medical Genetics, Yorkhill Hospitals. Increasing proportions of affected pregnancies screened, detected and terminated were observed, to a greater degree for anencephaly than for spina bifida. The relationships between uptake, sensitivity, compliance and terminations are described in the form of a simple arithmetic expression. In policy terms, further efforts are required to increase all three in order to improve the effectiveness of screening for spina bifida.     

Screening for congenital neural tube defects in a high-risk area: an epidemiological perspective.

Data from the Glasgow Register of Congenital Malformations were used to investigate the extent of the recent decline in the prevalence of anencephaly and spina bifida, and the contribution of antenatal screening to it. Over the period 1974-85 inclusive, 303 pregnancies with an anencephalic foetus were diagnosed, representing an "adjusted" prevalence of 1.9 per 1000 total births, of which 179 (59%) were terminated following antenatal screening. There were 364 pregnancies with a spina bifida foetus representing an "adjusted" prevalence of 2.3 per 1000 total births, of which 84 (23%) were terminated. Over the study period, the "adjusted" prevalence of anencephaly fell by 50% while the birth prevalence fell by 89%; the "adjusted" prevalence of spina bifida fell by 38% while the birth prevalence fell by 76%. It was concluded that although the birth prevalence of both defects (particularly anencephaly) would have declined substantially in the absence of screening, the West of Scotland programme should continue.     

Prenatal tea consumption and risks of anencephaly and spina bifida

PURPOSE: To evaluate the relationship between prenatal tea consumption and risk of anencephaly and spina bifida.METHODS: Data from the population-based Atlanta Birth Defects Case-Control Study were examined. Cases were infants with anencephaly (n = 122) or spina bifida (r = 154) and no other associated anomalies, and identified between 1968 and 1980. Controls were infants without birth defects (n = 3029) identified from birth certificates of the same birth cohort and frequency matched to cases by race, period of birth, and hospital of birth.RESULTS: Maternal tea consumption during the periconceptional period (3 months before through the first trimester of pregnancy) was reported at 82, 83.6, and 92.9% among controls, anencephaly, and spina bifida cases, respectively. With subjects whose mothers consumed no tea as a reference, odds ratios (OR) for tea consumption during the periconceptional period (adjusted for gender, race, period of birth, maternal age, education, alcohol consumption, smoking, and periconceptional multivitamins) were: anencephaly 0.9 (95% confidence limits (CI) 0.5-1.5); spina bifida 2.3 (CI 1.2-4.4). Odds ratios for spina bifida and number of cups of tea consumed/day were: 1-2 cups 2.1 (CI 1.1-4.0); 3+ cups 2.8 (CI 1.4-5.6). Consumption of other caffeinated beverages was not associated with risk for anencephaly or spina bifida.CONCLUSIONS: Further studies are warranted to corroborate and elucidate the observed association between tea consumption and spina bifida.     

中国出生缺陷高发地区出生缺陷的发生水平和流行病学特征

目的研究中国出生缺陷高发地区出生缺陷的发生水平,分析主要出生缺陷的分布和流行病学特征。方法在出生缺陷高发的山西省选择2个高发县作为调查现场,对调查地区2002年1月1日至2004年12月31日期间孕满20周及以上的所有出生人口开展了以人群为基础的出生缺陷回顾性调查。结果调查地区2002—2004年出生缺陷发生率为844.2/万,发生率位于前五位的出生缺陷包括腹股沟疝(182.2/万)、无脑儿(104.4/万)、先天性智力低下(79.4/万)、先天性心脏病(73.2/万)和脊柱裂(63.9/万),前五位出生缺陷占全部出生缺陷的60%。国内外出生缺陷统计分析一般不包括腹股沟疝、鞘膜积液、隐睾和先天性智力低下,如果不包括这四类出生缺陷,调查地区出生缺陷发生率为537.2/万,位于前五位的出生缺陷分别为无脑儿、先天性心脏病、脊柱裂、脑积水(40.5/万)和脑膨出(31.2/万)。男性出生缺陷发生率为966.2/万,明显高于女性(640.4/万)。孕产妇年龄<20岁组和>30岁组出生缺陷发生率明显高于20～24岁和25～29岁年龄组。低龄孕妇发生神经管畸形和先天性心脏病的风险甚至显著高于高龄孕妇,孕产妇年龄<20岁组神经管畸形和先天性心脏病的发生率分别是408.8/万和188.7/万,而>30岁组两类出生缺陷的发生率分别为204.8/万和91.0/万。出生缺陷发生率随着孕产次的增加而明显提高。结论中国高发地区出生缺陷的发生呈现出与其他地区不同的流行病学特征,尤其是神经管畸形异常高发。不仅是高龄孕妇,20岁以下的低龄孕妇同样是一些出生缺陷发生的高危险因素。     

Spina bifida and anencephaly prevalence--United States, 1991-2001.

Spina bifida and anencephaly are serious birth defects. To reduce the occurrence of these birth defects, the Food and Drug Administration authorized the fortification of all enriched cereal grain products with folic acid in March 1996, with compliance mandatory by January 1998. This report reviews data reported to CDC's National Center for Health Statistics (NCHS) regarding spina bifida and anencephaly prevalence for live births in the United States during 1991-2001. Since 1989, NCHS has compiled birth defect data from checkboxes that appear on birth certificates. For consistency in trends, this report uses data for 1991-2001 from all U.S. reporting areas except Maryland, New Mexico, and New York. Data for 2001 are preliminary. During 1996-2001, a 23% decline occurred in neural tube defects (spina bifida and anencephaly combined). Spina bifida declined 24% during this period, and anencephaly declined 21%. The United States has experienced declines in spina bifida and anencephaly cases since folic acid fortification of all enriched cereal grain products. The observed declines have translated into approximately 920 infants being born without these serious defects each year. Continued monitoring of the occurrence of spina bifida and anencephaly will be necessary to evaluate the effectiveness of folic acid fortification.     

The incidence of spina bifida in Sweden 1973-2003: the effect of prenatal diagnosis

BACKGROUND: Many studies have been conducted on the accuracy of prenatal ultrasound diagnosis of foetal CNS-malformations. These studies were mostly hospital-based or, sometimes, multicentre studies. We present here a population-based study of the prenatal diagnosis of spina bifida in Sweden over a period of 31 years. METHODS: We compared the number of newborns with spina bifida and the elective terminations because of the prenatal diagnosis of spina bifida for different periods. RESULTS: The rate of spina bifida among newborns diminished gradually from 0.55 per 1000 to 0.29 per 1000 during the study period. In M county the rate of spina bifida at birth decreased very rapidly and from 1993 onwards was about half of that in the rest of the country. CONCLUSION: There has been a decline in the rate of spina bifida at birth. This decline can be seen earlier in the southern part of the country, M county. The decline is probably, to a great extent, a consequence of prenatal ultrasound screening.     

Fetal pathology study of 88 cases of letal spina bifida

Lethal spina bifida continue to be frequent in Tunisia; we report 88 cases of letal spina bifida: 1.05 per thousand births. This pathology was more frequent with women. The up letal spina bifida situated is predominant with female and the dow spina bifida situated is frequent with male. We have noted an association with anencephalia (46 cases) and hydrocephaly (21 cases). Prevention is based on obstetric health care and hygiene dietetic advices to avoid alimentary deficit.     

Improved national prevalence estimates for 18 selected major birth defects--United States, 1999-2001

Continuing efforts are needed to improve surveillance for birth defects, which are the leading cause of infant mortality in the United States. Although state and local surveillance data indicate that approximately 3% of births are affected by any of 45 birth defects, no national estimates based on population-based birth defects surveillance have been available for specific types of birth defects other than neural tube defects (spina bifida and anencephaly). This report describes estimates of national prevalence and number of affected births in the United States each year during 1999-2001 for 18 selected major birth defects. The findings indicated that 10 of the 18 defects affected more than 1,000 infants each year in the United States. The conditions with the highest prevalence included orofacial clefts, which affect approximately 6,800 infants annually, and Down syndrome, which affects approximately 5,500 infants annually. Population-based national prevalence estimates of birth defects can help determine resource needs for basic and public health research and assist in planning for the health-care and educational needs of the U.S. population.     

Adverse pregnancy outcomes around incinerators and crematoriums in Cumbria,north west England, 1956-93

STUDY OBJECTIVE: To investigate the risk of stillbirth, neonatal death, and lethal congenital anomaly among babies of mothers living close to incinerators and crematoriums in Cumbria, north west England, 1956-93. DESIGN: Retrospective cohort study. Logistic regression was used to investigate the risk of each outcome in relation to proximity at birth to incinerators and crematoriums, adjusting for social class, year of birth, birth order, and multiple births. Continuous odds ratios for trend with proximity to sites were estimated. SETTING: All 3234 stillbirths, 2663 neonatal deaths, and 1569 lethal congenital anomalies among the 244 758 births to mothers living in Cumbria, 1956-1993. Main results: After adjustment for social class, year of birth, birth order, and multiple births, there was an increased risk of lethal congenital anomaly, in particular spina bifida (odds ratio 1.17, 95% CI: 1.07 to 1.28) and heart defects (odds ratio 1.12, 95% CI: 1.03 to 1.22) around incinerators and an increased risk of stillbirth (odds ratio 1.04, 95% CI: 1.01 to 1.07) and anencephalus (odds ratio 1.05, 95% CI: 1.00 to 1.10) around crematoriums. CONCLUSIONS: The authors cannot infer a causal effect from the statistical associations reported in this study. However, as there are few published studies with which to compare our results, the risk of spina bifida, heart defects, stillbirth, and anencephalus in relation to proximity to incinerators and crematoriums should be investigated further, in particular because of the increased use of incineration as a method of waste disposal.     

四维超声和MRI在胎儿隐性脊柱裂筛查中的应用及影响诊断准确性的因素分析

目的:探讨四维超声在胎儿隐性脊柱裂筛查中的应用及影响诊断准确性的因素分析.方法:选择在医院进行产前筛查,经普通超声检查疑似存在胎儿脊柱发育异常且不能被明确诊断的80名孕妇,分别采用四维超声和磁共振成像(MRI)检查,比较四维超声和MRI诊断方法诊断胎儿隐性脊柱裂的效果,分析影响四维超声诊断准确性的影响因素.结果:四维超...     

1996～2000年全国神经管缺陷的动态监测

目的：利用1996年1月至2000年12月期间中国出生缺陷监测网收集的资料,描述国产儿无脑,脊柱裂和脑膨出3种神经管缺陷（NTDs)的流行病学特征及其动态变化趋势。方法：采用以医院为基础的监测方法收集资料,调查对象为孕28周至产后7d住院分娩的围产儿,包括活产,死胎和死产。结果：共收集围产儿2218616列;神经管缺陷儿2873例。中国人围产儿NTDs总发生率为12．95／万,其中无脑,脊柱裂和脑膨出的发生率分别为5．02／万,6．30／万和1．64／万,总的NTDs和无脑畸形年度发生率呈下降趋势,男性NTDs发生率为9．75／万,女性的15．96／万,城市为7．76／万,农村为25．20／万,北方为19．90／万,南方为5．81／万,母龄别发生率在＜20岁和＞30岁组高于其他年龄组。NTDs围产儿早产占50．9％,低出生体重占50．6％,围产期病死率为77．8％。结论：中国围产儿NTDs发生率女性高于男性,农村高于城市,北方高于南方。年度发生率呈下降趋势,但高于其他国家同期水平。神经管缺陷儿出生素质差,围产期病死率高,预后不良。加强预防和产前诊断是降低发生率的有效措施。     

East Ireland 1980-1994: epidemiology of neural tube defects

STUDY OBJECTIVE: The objective of the study was to describe the epidemiology of neural tube defects (NTD) in the eastern region of Ireland using the EUROCAT register of congenital malformations. DESIGN, SETTING AND PATIENTS: EUROCAT registries monitor the prevalence of congenital anomalies in defined populations using multiple sources for case ascertainment. All cases of NTD on the Dublin EUROCAT register born between 1980 and 1994 were extracted and analysed. The crude birth prevalence rate for all NTD, spina bifida, anencephaly and encephalocoele were calculated for each year. Parameters measured were: sex ratio, stillbirth rate, proportion of low birth-weight babies (< 2500 g) and the proportion who were premature (< 37 weeks gestation). MAIN RESULTS: Of 821 NTD cases, 419 (51.0%) had spina bifida, 322 (39.2%) had anencephaly, 69 (8.4%) had encephalocoele and 11 (1.3%) were iniencephalic. The crude birth prevalence of NTD decreased fourfold from 46.9/10,000 births in 1980 to 11.6/10,000 in 1994. The downward trend ceased during the early 1990's. Younger mothers had significantly higher rates of NTD affected births. Twenty two per cent of NTD cases had additional non-central nervous system anomalies. In 40 cases, there was a previous family history of NTD in siblings. Seasonal effects in birth prevalence were observed. Birth notification was the most frequent mechanism of ascertainment. CONCLUSION: There was a marked fall in the birth prevalence of NTD during the 15 year period. This change was real and not accounted for by pre-natal screening and diagnostic practises with termination of pregnancy, which is not legally permissible in Ireland. Dietary factors may have had an influence. Rates of NTD in this region are still higher than many other parts of Europe. Primary prevention strategies through increased folic acid intake are necessary to further reduce NTD affected births.     

Seasonal variation in the frequency of anencephalus and spina bifida births in the United Kingdom.

There have been statistically significant seasonal variations of annencephalus and spina bifida in each country of the United Kingdom during 1964-79 with the exception of anencephalus births in Northern Ireland. The seasonal peaks, where discernible, are in phase. Embryos appear to develop anencephalus most commonly in May-June and spina bifida in July.     

The changing prevalence of neural tube defects: a population-based study in the north of England, 1984-96. Northern Congenital Abnormality Survey Steering Group

Using data from the Northern Congenital Abnormality Survey, we describe trends in the prevalence of neural tube defects (NTDs), maternal age-specific prevalence, outcome of pregnancy and the sensitivity of antenatal diagnosis of NTD-affected pregnancies in the Northern Region during 1984-96. This population-based sample consisted of 934 NTDs: there were 403 (43.1%) with anencephaly, 472 (50.5%) with spina bifida and 59 (6.3%) with encephalocele. The total prevalence at birth was 17.9 per 10,000 births and terminations (95% confidence interval [CI] = 16.7, 19.0) with a significant reduction over time (chi(2) for trend = 7.2; P = 0.007). The overall birth prevalence was 5.6 per 10,000 births [95% CI = 5.0, 6.3]; there was also a significant reduction in birth prevalence with time (chi(2) for trend = 68.3; P < 0.0001). Maternal age-specific prevalence rates decreased with increasing age. The proportion of NTD pregnancies terminated increased from 60.3% (325 cases) during 1984-90 to 78.6% (293 cases) during 1991-96, whereas the proportion of livebirths declined from 31.7% (171 cases) to 15.0% (56 cases) (P < 0.001). The sensitivity of antenatal diagnosis was consistently high for anencephaly (98%) and increased significantly for spina bifida from 60% during 1984-90 to 85% during 1991-96 (P < 0.05). Ascertainment of all cases of NTD in the Northern Region revealed a twofold reduction in birth prevalence between 1984-90 and 1991-96. This has resulted from improvements in the accuracy of antenatal detection of NTD-affected pregnancies with an increase in terminations of pregnancy.     

Hospitalization for urinary tract infections and the quality of preventive health care received by people with spina bifida

BackgroundThe preventive health care needs of people with disabilities often go unmet, resulting in medical complications that may require hospitalization. Such complications could be due, in part, to difficulty accessing care or the quality of ambulatory care services received.ObjectiveTo use hospitalizations for urinary tract infections (UTIs) as a marker of the potential quality of ambulatory care services received by people affected by spina bifida.MethodsMarketScan inpatient and outpatient medical claims data for 2000 through 2003 were used to identify hospitalizations for UTI, which is an ambulatory care sensitive condition, for people affected by spina bifida and to calculate inpatient discharge rates, average lengths of stay, and average medical care expenditures for such hospitalizations.ResultsPeople affected by spina bifida averaged 0.5 hospitalizations per year, and there were 22.8 inpatient admissions with UTI per 1000 persons with spina bifida during the period 2000–2003, in comparison to an average of 0.44 admission with UTI per 1000 persons for those without spina bifida. If the number of UTI hospitalizations among people affected by spina bifida were reduced by 50%, expenditures could be reduced by $4.4 million per 1000 patients.ConclusionsConsensus on the evaluation and management of bacteriuria could enhance clinical care and reduce the disparity in UTI discharge rates among people affected by spina bifida compared to those without spina bifida. National evidence-based guidelines are needed.     

Effect of folic acid fortification on the incidence of neural tube defects

Amarin ZO, Obeidat AZ. Effect of folic acid fortification on the incidence of neural tube defects. Paediatric and Perinatal Epidemiology 2010. In a few countries enriched cereal grains have been fortified with folic acid to reduce the incidence of neural tube defects. The objective of this study was to analyse the effect of folic acid fortified foods on the incidence of neural tube defects in live newborns at Princess Badea Teaching Hospital, in the north of Jordan, before and after the national food fortification with folic acid was implemented. For the 7‐year period from 1 January 2000 to 31 December 2006, we retrospectively extracted the total number of births at Princess Badea Hospital, as well as the number of pregnancies affected by spina bifida and anencephaly, per 1000 births during the periods before (2000–01), during (2002–04) and after (2005–06) folic acid fortification of grain products, was implemented. Neural tube defects were defined in accordance with the International Classification of Diseases, 10th revision (ICD‐10): anencephaly, encephalocele and spina bifida. A total of 78 subjects with neural tube defects were recorded among 61 447 births during the study period. The incidence of neural tube defects decreased from 1.85 per 1000 births before fortification [95% confidence interval (CI) 1.2, 2.4] to 1.07 per 1000 births during the fortification period [95% CI 0.7, 1.5], and 0.95 after full fortification [95% CI 0.5, 1.5], a 49% reduction. The difference between incidence of neural tube defects in the periods before and after food fortification with folic acid was statistically significant. We conclude that food fortification with folic acid was associated with a significant reduction in the rate of neural tube defects in north Jordan.     

A population-based case-control study of risk factors for neural tube defects in four high-prevalence areas of Shanxi province, China

Shanxi province in Northern China has one of the highest reported prevalence rates of neural tube defects (NTD) in the world. To explore the risk factors for NTDs in Shanxi province, we carried out a population-based case-control study in four selected counties with prevalence rates >10 per 1000 births during 2003. Using a multi-logistic regression model analysis (alpha = 0.10), 158 NTD cases were compared with 226 control mothers. Maternal factors significantly associated with increased risk for an NTD were a primary school education or lower (adjusted odds ratio [OR] 2.32, 95% confidence interval [CI] 1.09, 4.97); a history of a previous birth defect-affected pregnancy (adjusted OR 5.27, 95% CI 0.98, 28.37); history of a fever or 'cold' (adjusted OR 3.36, 95% CI 1.68, 6.72); use of analgesic and antipyretic drugs (adjusted OR 4.89, 95% CI 0.92, 25.97); daily passive exposure to cigarette smoke (adjusted OR 1.60, 95% CI 0.94, 2.73); poor ventilation during heating (adjusted OR 3.91, 95% CI 0.75, 20.81); and consumption of >or= six meals per week containing pickled vegetables (adjusted OR 3.86, 95% CI 1.11, 13.47) during pregnancy. Factors which appeared to be protective were meat consumption one to three times per week (adjusted OR 0.62, 95% CI 0.37, 1.06), or >or= four times per week (adjusted OR 0.28, 95% CI 0.11, 0.77); and legume consumption >or= six times per week (adjusted OR 0.39, 95% CI 0.17, 0.89). Differences in risk were found between the two most common phenotypes, anencephaly and spina bifida. Most of the environmental factors had stronger positive and negative associations with risk for anencephaly rather than spina bifida, whereas history of a previous birth defect-associated pregnancy, as well as legume consumption, were more strongly associated with the risk for spina bifida than for anencephaly. The findings suggest that aetiological heterogeneity may exist between anencephaly and spina bifida.     

中国神经管畸形儿在高发和低发区的性别分布及其出生结局

目的 对中国神经管畸形(NTD)高发和低发区畸形儿的性别及出生结局的流行病学特点进行描述性分析。方法 利用1992～1994年期间“中美预防神经管畸形合作项目”监测资料,按照国际上采用的分类方法,将NTD分为4类,即无脑畸形、脑膨出、高位和低位脊柱裂,再将每一类按照是否合并其他系统畸形分为单纯与合并型,进行高低发区不同类型NTD的男女性别率、性别率比和出生结局的研究,调整城乡、季节和种类,计算调整后的性别率。结果 共监测到326874总产数(包括孕20周及以上的活产、死胎和死产),NTD784例,北方高发区女性无脑畸形发生率(1．30／1000女性总产数)和高位脊柱裂发生率(3．99／1000女性总产数)高于男性(0．66／1000男性总产数和1．66／1000男性总产数),其调整率女性大约是男性的1．8～2．1倍;南方低发区女性高位脊柱裂发生率(0．32／l000女性总产数)和低位脊柱裂发生率(0．21／1000女性总产数)高于男性(0．10／1000男性总产数和0．09／1000男性总产数),其调整率女性是男性的1．3～1．6倍;单纯NTD占全部病例的80％以上,并且单纯NTD女性发生率(2．57／1000女性总产数)显著高于男性(1．40／1000男性总产数),合并型：NTD男女性别发生率(0．36／1000和0．49／1000)的差异无显著性;死产中以高位脊柱裂(44．95％)、活产中以低位脊柱裂(40．64％)占比例较高。死胎中高位脊柱裂和无脑畸形分别占47．06％和35．56％。结论 南方低发区和北方高发区性别率差异随NTD种类而不同,提示可能存在随NTD率增高,女性高位脊柱裂和无脑畸形所占比例有增大趋势。无脑畸形、高位与低位脊柱裂之间可能存在不同的遗传和环境因素。     

2006-2012年北京市顺义区神经管缺陷流行特征

目的 描述北京市顺义区2006-2012年神经管缺陷(neural tube defects,NTDs)的流行病学特征,为NTDs的预防提供参考依据。方法 利用顺义区的出生缺陷监测资料,描述NTDs及其亚型的患病率和变化趋势。结果 2006-2012年顺义区NTDs患病率为12.6/10⁴(监测时限为孕13周至产后7 d),无脑畸形、脊柱裂、脑膨出的患病率依次为6.7/10⁴、4.9/10⁴、1.0/10⁴。2006-2012年NTDs总患病率未见下降趋势,各亚型中脊柱裂患病率下降趋势有统计学意义(P<0.05)。户籍人口NTDs患病率(6.8/10⁴)低于流动人口(20.0/10⁴)(P<0.01)。结论 7年间顺义区NTDs患病率无趋势性变化,但脊柱裂患病率有下降趋势。顺义区还需进一步加强流动人口NTDs的预防。     

High incidence of neural tube defects in Bursa, Turkey

A radiological survey of 1204 members of the population of Bursa revealed a high prevalence of spina bifida occulta (16.3%). Hospital deliveries in the area also showed a high incidence of anencephalus and spina bifida aperta (5.8 per 1000 total births) in the years 1983 to 1986. In the first 6 months of 1987, however, there was an increase in incidence to 20 per 1000 births (P less than 0.01). The possibility is raised that the Chernobyl disaster of May 1986 might have resulted in the elevation of the rate in an already susceptible population.