Prevention of folic acid-preventable spina bifida and anencephaly

The results of the British Medical Research Council's randomized controlled trial proved that folic acid can prevent spina bifida and anencephaly. The trial provided critical scientific data upon which to base public health policy for preventing folic acid-preventable spina bifida and anencephaly. Within weeks of publication of the results, the Centers for Disease Control and Prevention in the US developed and issued guidelines for women who had had a pregnancy affected by spina bifida or anencephaly. A year later, the US Public Health Service issued the recommendation that all women of child-bearing age who are capable of becoming pregnant should consume 0.4 mg of folic acid per day. The Public Health Service needed a year to make inferential judgements about dose, target groups, safety, timing of ingestion, and existing and proposed vitamin and drug policies and regulations. Current policy discussions concern whether to permit manufacturers of vitamins or food products to claim that folic acid will prevent folic acid-preventable spina bifida and anencephaly and whether to allow a food staple to be fortified with folic acid.

Tocolytic magnesium sulfate exposure and risk of cerebral palsy among children with birth weights less than 1,750 grams

The authors examined the relation between intrapartum magnesium sulfate exposure and risk of cerebral palsy in a case-control study of low birth weight children designed to control for confounding by the clinical indications for magnesium in pregnancy. Case children (n = 97) included all singleton children with cerebral palsy who were born in 1985-1989 in Atlanta, Georgia with a birth weight less than 1,750 g and whose mothers had not had a hypertension-related disease during pregnancy. Control children (n = 110) were randomly selected from the infant survivors using identical selection criteria. Data on magnesium sulfate exposure, labor and delivery, and infant characteristics were abstracted from hospital records. The authors found no association between exposure to magnesium sulfate and cerebral palsy risk (odds ratio = 0.9; 95% confidence interval: 0.3, 2.6) either in all children or in subgroups with varying likelihoods for exposure to magnesium. However, the association did vary by birth weight, with a protective effect being seen in children born weighing less than 1,500 g and an elevated risk in children with birth weights of 1,500 g or more; all confidence intervals included 1.0 except for the combined <1,500 g group. Several ongoing randomized clinical trials of magnesium and cerebral palsy may shed more definitive light on this relation.

Doubling the number of women consuming vitamin supplement pills containing folic acid: an urgently needed birth defect prevention complement to the folic acid fortification of cereal grains

The major known environmental causes of birth defects are ancient agents that have been in the environment for centuries but have been only recently discovered-rubella, alcohol, and folic acid deficiency. In the United States, we have made great progress in preventing congenital rubella syndrome. We also have a great opportunity to prevent spina bifida and anencephaly (SBA) by increasing the number of women who daily consume vitamin supplements containing folic acid. Even with the recently announced grain fortification regulations, there are 45 million women unprotected from an SBA-affected pregnancy. This article suggests that a substantial educational campaign could, over a 5-year period, double the number of women consuming folic acid supplement pills and make a substantial contribution toward preventing SBA.

5,10 Methylenetetrahydrofolate reductase genetic polymorphism as a risk factor for neural tube defects

Persons with a thermolabile form of the enzyme 5,10 methylenetetrahydrofolate reductase (MTHFR) have reduced enzyme activity and increased plasma homocysteine which can be lowered by supplemental folic acid. Thermolability of the enzyme has recently been shown to be caused by a common mutation (677C-->T) in the MTHFR gene. We studied 41 fibroblast cultures from NTD-affected fetuses and compared their genotypes with those of 109 blood specimens from individuals in the general population. 677C-->T homozygosity was associated with a 7.2 fold increased risk for NTDs (95% confidence interval: 1.8-30.3; p value: 0.001). These preliminary data suggest that the 677C-->T polymorphism of the MTHFR gene is a risk factor for spina bifida and anencephaly that may provide a partial biologic explanation for why folic acid prevents these types of NTD.

More folic acid for everyone, now

Research during the last 5 years has made it clear that people who do not take folic acid supplements are at increased risk for functional folate deficiency, which has been proven to cause spina bifida and anencephaly and also has been associated with an increased risk for occlusive cardiovascular disease. The overriding folate policy issue is how to increase dramatically the folate consumption of 75% of the population who are now consuming 0.4 mg of folic acid in a supplement. The most expeditious way to increase consumption is through fortification of a food staple. Public health programs are also needed to educate people about the vital importance of increased consumption of folic acid vitamin supplements and of food rich in natural folates. It is urgent that fortification of cereal-grain products be implemented now. The level proposes by FDA would accomplish some prevention, but much more prevention would occur if the fortification were 2.5 times that level. Fortification at the higher level would prevent about 1000 spina bifida and anencephaly birth defects each year and perhaps as many as 50,000 premature deaths each year from coronary disease. Available data have not demonstrated that increasing consumption of folic acid by 0.1 to 0.25 mg of folic acid a day is harmful. If a policy needs to be established on the assumption that people who take vitamin supplements could be harmed, a good policy option ia available; require that all folic acid vitamin supplements also contain 0.4 mg of vitamin B-12.

A multiple-source method for studying the prevalence of developmental disabilities in children: the Metropolitan Atlanta Developmental Disabilities Study

The Metropolitan Atlanta Developmental Disabilities Study is the first US, population-based epidemiologic study of the prevalence of mental retardation, cerebral palsy, hearing impairment, and visual impairment among school-age children. The study population consisted of children who were 10 years of age between 1985 and 1987 and whose mothers were residents of the five Georgia counties of Clayton, Cobb, DeKalb, Fulton, and Gwinnett at the time of the child's birth. Since children with developmental disabilities are identified by and receive services from various health, social service, and education systems, a multiple-source case identification method was used. This study is unique in that individual school records were used to identify children with the four disabilities. Use of a multiple-source method made it possible to confirm specific conditions and to classify subtypes of disabilities. About 95% of the children with one or more of these four disabilities were initially identified through the school systems. This approach is much less costly than conducting medical and psychologic assessments on populations of children. In addition, this method made it possible to estimate accurately the "administrative prevalence" of these disabilities (ie, the number of children previously identified with these disabilities for the purpose of providing services). The prevalence rates found in this study, per 1000 10-year-old children, were as follows: mental retardation, 10.3; cerebral palsy, 2.0; hearing impairment, 1.0; and visual impairment, 0.6.(ABSTRACT TRUNCATED AT 250 WORDS)

Teratogen update: valproic acid

Valproic acid use during pregnancy results in an absolute risk for spina bifida of 1-2%. This increased risk is comparable to the recurrence risk for neural tube defects and warrants informed counselling and access to prenatal diagnosis. There is no substantial evidence that valproic acid use increases the risk for other specific major malformations above the increased risk due to maternal epilepsy. Valproic acid may cause a characteristic pattern of minor facial malformations. Further definition and confirmation are required, and the magnitude of the risk needs to be determined. There are inadequate data to assess the magnitude, if any, of the risks for postnatal growth abnormalities and developmental disabilities associated with the use of valproic acid during pregnancy. Birth-defect monitoring programs and international collaboration among the staffs of monitoring programs played a major role in determining that valproic acid is a human teratogen.

Frequency of human congenital malformations

Birth defects are important health problems. They are the leading cause of infant mortality, the fifth leading cause of premature years of life lost, and important contributors to our nation's chronic disease burden. Researchers have been successful in finding a few causes of birth defects; however, the etiology of the majority of birth defects remains unknown and thus hampers our ability to prevent these diseases. Clinicians who care for patients with birth defects can play an important role in etiologic research by developing good and testable etiologic hypotheses. Epidemiologists must then use these hypotheses and those provided by scientists working with experimental animals to design studies that can test these hypotheses.

Survival of infants with spina bifida--Atlanta, 1972-1979

We studied the survival of a population-based cohort of 154 infants with spina bifida who were born during the eight-year period from 1972 through 1979 to residents of Atlanta. Our objectives were to describe the cohort's survival experience and to explore relationships between clinical characteristics and survival. Overall, 57% of the cohort survived one year or more. This figure is misleading, however, because it conceals important differences in survival among subgroups of affected infants. From univariate analyses, we observed significant differences in survival among infants categorized by year of birth, birth weight, the open-closed status of the defect, the highest level of the defect on the spine, the presence of multiple major birth defects, and the presence of hydrocephalus at birth. More infants born in the late 1970s survived their first year of life than infants born in the early 1970s; infants with open defects had lower survival than those with closed defects; and infants whose defects were low on the spine had better survival than those whose defects were higher. When comparing the survival experience of this cohort with that of other groups from other areas or from more recent years, health workers must consider referral biases and differences in the distribution of clinical characteristics.

Trends in clinical characteristics of infants with spina bifida--Atlanta, 1972-1979

In Atlanta, the birth prevalence of spina bifida declined from 10.1 per 10,000 live births in 1972-1973 to 5.8 per 10,000 live births in 1978-1979. This trend cannot be explained by use of prenatal diagnosis, because it was unavailable in Atlanta until 1976, and even in the late 1970s was not used widely. To determine if this decrease was associated with changes in the distribution of clinical characteristics among infants with spina bifida, we reviewed the medical records of a population-based group of 154 infants with spina bifida, born in Atlanta during the eight-year period from 1972 through 1979. Distribution by the highest level of the defect on the spine did not change during these years. The proportions of infants with isolated spina bifida (ie, no other major malformations) and with open spina bifida (ie, not covered by skin) did, however, decrease. When we examined these two characteristics simultaneously, we found declines in both the proportion of infants with open-isolated spina bifida and the birth prevalence of infants with open-isolated spina bifida. If this trend persists, it will have important implications for workers involved with prenatal alpha-fetoprotein screening and researchers investigating the etiology of spina bifida.

Prenatal diagnosis of pericentric inversion of chromosome No. 17 in a twin pregnancy

Although prenatal genetic diagnosis can usually provide prospective parents with information as to whether their fetus is affected with certain genetic conditions, the presence of twins and the uncertainty about the phenotype of some chromosome variations pose a major dilemma and make genetic counseling very difficult. Here, a case report of an unusual chromosome aberration (pericentric inversion of chromosome no. 17) in a twin pregnancy which was originally suspected to be monoamniotic but later proved to have two sacs was presented.

Use of prenatal diagnosis among parents of infants with spina bifida in Atlanta, Georgia, 1976-1979

A follow-up was made of the parents of a population-based cohort of 154 infants with spina bifida who were born in Atlanta during 1972-1979. We interviewed the parents of these infants and, for pregnancies after the spina bifida-affected birth, the ratio of use of prenatal diagnosis and the rate of recurrence of spina bifida were ascertained. Among 43 pregnancies which occurred in 1976 or later, and which occurred after a spina bifida-affected birth, prenatal diagnosis was used for 27 pregnancies (63%). For whites, among full siblings born after a spina bifida-affected birth, the recurrence rate for spina bifida was 2% (1/51). For blacks, among seven full siblings born after a spina bifida-affected birth, none was affected. Prenatal diagnosis appears to be well accepted among these parents of infants with spina bifida.

Clinical interpretation of maternal serum alpha-fetoprotein concentrations

Concentrations of maternal serum alpha-fetoprotein provide the basis for decisions to proceed to ultrasonography and amniocentesis in the multistaged screening/diagnostic process used for the prenatal detection of open neural tube defects, abdominal wall defects, and twins. The concentration of maternal serum alpha-fetoprotein at or above which women should be advised that amniocentesis is available (cutoff levels for amniocentesis) varies, depending upon a number of factors, such as maternal weight, race, residence, and gestational age. We briefly describe a methodology for computing the predicted risks of fetal conditions associated with a given concentration of maternal serum alpha-fetoprotein adjusted for important variables. This adjustment methodology provides a straightforward means for clinical laboratories to report results of assays of maternal serum alpha-fetoprotein in terms of predicted risks, to facilitate understanding by the physician and patient of the clinical meaning of the results of maternal serum alpha-fetoprotein testing.

Population and case-control surveillance in the search for environmental causes of birth defects

An important national health goal is to reduce morbidity attributable to birth defects and developmental disabilities. Population-based surveillance has made notable contributions toward preventing these problems; it is also useful in monitoring changes in their incidence and in helping to identify reproductive hazards in the environment. The Metropolitan Atlanta Congenital Defects Program of the Centers for Disease Control is a model for such surveillance activities. Its register contains data on birth defects of all infants born in the five-county metropolitan area since 1976. Information on all major malformations discernible by physical examination is collected by the register staff. Mothers of babies with selected major malformations are interviewed at length. The register data base permits testing of new hypotheses concerning birth defects. It has speeded an extensive study of the possible effects of military service in Vietnam on the risk of having a baby with a birth defect. In addition, because of their special skills, program staff have made contributions to genetic services and to the development of national policy on maternal serum alpha fetoprotein.

Estimates of birth prevalence rates of spina bifida in the United States from computer-generated maps

A computer-generated mapping procedure was developed to estimate geographic and race-specific birth prevalence rates of open spina bifida. The estimates are based on birth certificate data adjusted for underascertainment. Separate maps were produced for white births and black births. For both races there is a general decreasing rate of spina bifida from east to west. The highest rates are eight per 10,000 total births for whites in Southern Appalachia, and the lowest rates are less than one per 10,000 for blacks in the Rocky Mountain states and the Pacific Northwest. Until more exact data are available, these maps represent the best current available data on racial and geographic birth prevalence rates in the United States. They are useful for program planning and as an aid in interpreting maternal serum alpha-fetoprotein levels to detect neural tube defects.

Genetic services in the United States

In fiscal years 1979 and 1980, the Genetic Diseases Service Branch of the Health Services Administration funded 34 state genetic service programs in the United States through monies from the National Genetic Diseases Act (PL 94-278) of 1976. During the two-year period, 131,818 at-risk individuals were provided with genetic counseling. Analyses of amniotic fluid were performed on 42,003 specimens, with 436 abnormal fetuses (1%) detected. Utilization ratios of amniocentesis for advanced maternal age ranged from a low of 5% to a high of 49%. Screening programs for inborn errors of metabolism reported testing 3, 158,521 specimens. The numbers of affected children detected nationally were 195 with phenylketonuria (1:16,000), 536 with hypothyroidism (1:5,900), 25 with galactosemia (1:39,685), eight with maple syrup urine disease (1:86,984), and eight with homocystinuria (1:139,008).

Maternal age and births in the 1980s

Projections from the US Bureau of the Census show that as the large "baby boom" cohort ages in the 1980s, the percentage of births to women 35 years or older will increase by 37%, while the percentage of births to teenaged women, the small post-baby-boom cohort, will decrease by 32%. Between 1980 and 1990, for women aged 35 to 44 years, fertility rates are projected to increase modestly, whereas for teenagers aged 15 to 19 years, fertility rates are projected to decrease modestly. Assuming that half of pregnant women aged 35 years or older request prenatal chromosomal diagnosis, an estimated 1.1 million pregnant women aged 35 years or older will request this service during the 1980s, increasing substantially the demand for it. Simultaneously, demand for prenatal care for teenagers will decrease, due to the decrease in births to teenagers.

Congenital malformations surveillance: two American systems

As part of its epidemiologic studies of congenital malformations, the Centers for Disease Control (CDC) conducts two birth defects surveillance systems in the United States. The Metropolitan Atlanta Congenital Defects Programme (MACDP) is an intensive surveillance system using several methods to identify infants born with birth defects in the Atlanta area. The Birth Defects Monitoring Programme (BDMP) is a nationwide surveillance system that monitors 1 million births per year, about a third of all births in the U.S. It relies on diagnoses from newborn discharge summaries to ascertain affected infants. The systems were originally designed to detect potential 'epidemics' of birth defects that could occur following the widespread dissemination of new teratogens similar to thalidomide. In addition to monitoring, they have also proved to be useful resources for a variety of studies of the epidemiology of birth defects.

Rh hemolytic disease of the newborn: using incidence observations to evaluate the use of RH immune globulin

During the 1970s, the crude incidence of Rh hemolytic disease of the newborn (RhHDN) in the United States dropped 65 per cent---from 40.5/10,000 total births in 1970 to 14.3/10,000 total births in 1979. Since the risk of RhHDN is directly associated with birth order, changes both in birth order-specific RhHDN incidence rates and in the birth order distribution would be expected to influence crude RhHDN incidence. Review of birth order-specific incidences ascertained in Connecticut, 1972-1977, shows that incidence was stable for first and second births, whereas it dropped significantly for third and fourth births. Due to the nearly complete use of Rh immune globulin (RhIG) in Connecticut during these years, the drop in these specific rates is best attributed to this prevention strategy. Nationwide, during the 1970s, the annual percentages of fourth and higher order births decreased from 18 per cent to 10 per cent. We estimate that some 30 per cent to 40 per cent of the 1970-1979 drop in the crude rate is attributed to changes in the birth order distribution, whereas 60 per cent to 70 per cent of the drop is attributed to RhIG. However, comparison of pooled incidences for 1972-1974 and 1975-1977 observed in Connecticut for first births and births to 15-19 year olds showed significant increases for both groups in 1975-1977. Further study of specific trends from other areas is needed to confirm these observations. Also needed is investigation of likely causes of sensitization among these teenaged, primiparous women.

Down's syndrome. Recent trends in the United States

The crude incidence of Down's syndrome (DS) in the United States is currently about 1/1,000 births. Reduction in the proportion of births to women 35 years and older can account for a halving of the estimated percentage of DS births to this age group and a drop in the estimated crude incidence of DS from 1.33/1,000 births in 1960 to 0.99/1,000 births in 1978. Epidemiologic studies suggest that among women 35 years and older, the risk of having a child with DS has not changed. With the present distribution of maternal ages, prenatal diagnosis among women 35 years and older can result in no more than a 20% decrease in the crude incidence of DS. With continued use of prenatal diagnosis among older gravidas, upward of 80% of DS births will occur to younger mothers.

Is Bendectin a teratogen?

We studied the first-trimester exposure to Bendectin for several major categories of birth defects among infants ascertained through the Metropolitan Atlanta Congenital Defects Program from 1968 to 1978. No associations were found between any of these defect categories and Bendectin exposure. An association, however, was found for the amniotic bands cases--a subgroup of limb reductions. We stratified our data to reflect the 1976 change in formulation when one of the three ingredients was removed. An association was found between esophageal atresia and the three-ingredient product and another between encephalocele and the two ingredient product. These statistical associations do not establish a causal relationship between Bendectin and the birth defects we studied. Furthermore, even if the associations are causal, the implied risk is extremely low, approximately one in 1,000 births.

Utilization of prenatal genetic diagnosis in women 35 years of age and older in the United States, 1977 to 1978

As a measure of access to and acceptability of prenatal chromosomal diagnosis among older gravidas, we determined the ratio of use of prenatal diagnosis among women 35 years of age and older in Alabama, California, Manhattan, and Nebraska for the period 1977-1978. Utilization ratios were higher in 1978. Overall, utilization ratios were between 6% and 28%, well below the adjusted rates of 40% to 50% found in certain United States and British localities. Urban women tended to have higher utilization ratios than had rural women, and white women had higher ratios than had black women. Ratios were extremely low for black and rural residents. The oldest women (those greater than or equal to 40 years), who were at fivefold greater risk than women 35 to 36 years of age, had less than a onefold increase in utilization over the latter groups. The vast majority of older gravidas initiated prenatal care sufficiently early in their pregnancies to receive prenatal diagnosis. Current program strategies need to ensure access to prenatal diagnosis, especially for women greater than or equal to 40 years of age, women who are black, and women who live in rural areas.

Prenatal chromosomal diagnosis. Racial and geographic variation for older women in Georgia

In a study of Georgia women aged 40 years and older, 15% made use of prenatal chromosomal diagnosis. There was, however, substantial racial and geographic variation, ranging from a use ratio of 60% among whites in two large urban counties to 0.5% among blacks outside Augusta and Atlanta health districts. This simple population-based epidemiologic analysis suggests that future program planning for genetic services in Georgia should address ways to increase access by rural women, especially blacks. Similar analyses in other states could be used for planning genetic services.

Reducing birth defect risk in advanced maternal age

The incidence of birth defects increases with maternal age. Recent advances in fetal diagnosis, coupled with elective abortion, offer the older pregnant woman an opportunity to reduce this risk. To determine the magnitude of potential risk reduction, we reviewed the maternal age-specific incidence of infants born with one or more severe birth defects in metropolitan Atlanta from 1968 to 1975, removing from analysis certain anomalies that were preventable by currently available methods. For women aged 35 to 44 years, the risk of bearing an infant with a severe birth defect was reduced to a level comparable with that for younger women. Despite prenatal diagnosis and elective abortion, the risk for women aged 45 years or older, although reduced considerably, was two times greater than that for women aged 34 years or younger.

Maternal serum alpha-fetoprotein screening: a cost-benefit analysis

The prenatal detection of fetal neural tube defects (NTD) is now possible by means of a multi-tiered program utilizing maternal serum alpha-fetoprotein (MSAFP) screening coupled with ultrasonography and amniocentesis where indicated. This paper considers the economic consequences of screening for fetal NTD a theoretical cohort of 100,000 pregnant women at risk of having an affected fetus who would elect to terminate their pregnancies if an affected fetus were found. The cost of the program was balanced against the benefits of the program, such as the averted costs of institutionalization, medical care, and the like. The total cost of the program to screen 100,000 such women was calculated to be $2,047,780, or slightly over $20 per woman screened, while the total economic benefits exceeded $4,000,000.

Congenital hypothyroidism control programs. A cost-benefit analysis

Comprehensive screening programs to control congenital hypothyroidism (CH), a preventable form of mental retardation, are being considered by some public health agencies. The proposed programs would test neonates' blood for thyroxine and, if warranted, provide follow-up testing and therapy. The estimated cost of detecting a single case of CH is $9,300, which includes specimen collection, laboratory analysis, and retesting of border-line cases. The present value of the treatment costs of CH adds $2,500 per case, a total cost of $11,800 per case detected and child treated. The economic benefits (averted costs of institutionalization and special education and increased productivity of the affected person) are estimated to have a present value of $105,000 per case, yielding a cost-benefit ratio of 1:8.9.