Birth Prevalence Rates Research Articles

Clinical and epidemiologic studies of cleft lip and palate in the Philippines.

Clinical and epidemiologic studies of defined geographic populations can serve as a means of establishing data important for genetic counseling and as a first step in identifying strategies best suited for identification of causes. Under the sponsorship of Operation Smile International, clinical, genetic, and epidemiologic studies were carried out at six sites within the Philippines between 1989 and 1996. Patients who were being evaluated for surgical repair of craniofacial anomalies (primarily clefts of the lip and palate) were briefly examined for the presence of associated anomalies, and a family history was obtained to look for the frequency of cleft lip and palate in siblings. Birth records of 47,969 newborns over an 8-year period at one hospital in Bacolod City in the province of Negros Occidental were reviewed. Medical records of infants born with clefts of the lip and/or palate and other major anomalies were reviewed and birth prevalence rates calculated. Findings include a birth prevalence of 1.94 per 1000 live births for cleft lip with/without palate in the Philippines. Recurrence rates in siblings for nonsyndromic clefts of the lip and palate were 23 per 1000 for cleft lip with or without cleft palate, and 14 per 1000 for cleft palate only. The percentage of clefts associated with multiple anomalies was 21% at birth and 6% for individuals examined during the screening process, providing evidence for a high postnatal death rate. These data provide groundwork for additional etiologic studies including segregation analysis and molecular genetic studies involving linkage or association, as well as for studies of environmental contributions to clefting such as vitamin deficiencies. Preliminary molecular analysis using an association approach is reported in a companion paper. The findings suggest a high incidence of cleft lip and palate in native-born Filipinos.

Trends and Outcomes After Prenatal Diagnosis of Congenital Cardiac Malformations by Fetal Echocardiography in a Well Defined Birth Population, Atlanta, Georgia, 1990–1994

In this study we used a population-based approach to assess the impact of fetal echocardiography on a well defined birth population with nearly complete ascertainment of cardiac defects. Although fetal echocardiography is being used more frequently in the prenatal diagnosis of congenital cardiac malformations, its impact on the diagnosis and surveillance of cardiac defects has not been described in defined populations. All stillborn and live-born infants with diagnosed cardiac defects and whose mothers resided in the metropolitan Atlanta area from January 1990 through December 1994 were ascertained through an established birth defects surveillance system. All fetuses with cardiac defects diagnosed prenatally by a pediatric of cardiac defects, diagnostic trends and adverse fetal outcomes were described. We identified 1,589 infants with congenital cardiac malformations, for a live-birth prevalence rate of 8.1/1,000 (95% confidence interval [CI] 7.8 to 8.6). Overall, 97 (6.1%) of these cases of cardiac malformations were diagnosed prenatally. The proportion of cardiac defects diagnosed prenatally rose from 2.6% in 1990 to 12.7% in 1994, a nearly fivefold increase. The proportion of cardiac defects diagnosed prenatally during the study varied by the type of defect, from a low of 4.7% for atrial septal defects to a high of 28% for hypoplastic left heart syndrome. Prenatally diagnosed cardiac malformations were associated with a high incidence of infant mortality (30.9%, 95% CI 2.4 to 5.4) and fetal wastage (17.5%, 95% CI 6.2 to 11.3). These data show that fetal echocardiography is being used increasingly in the prenatal diagnosis of congenital cardiac malformations in metropolitan Atlanta. Few pregnancy terminations were reported as a result of such diagnoses. However, the study had limited power (10%) to detect a meaningful decrease in birth prevalence rates for congenital heart disease. In addition, survival of infants was not improved after prenatal diagnosis with fetal echocardiography.

Epidemiological analysis of rare polydactylies.

This work includes all cases with extra digits (polydactyly) registered from a birth sample of over four million births aggregated from two comparable birth series: the Latin-American Collaborative Study of Congenital Malformations: ECLAMC (3,128,957 live and still births from the 1967 to 1993 period), and the Spanish Collaborative Study of Congenital Malformations: ECEMC (1,093,865 livebirths from April 1976 to September 1993, and 7,271 stillbirths from January 1980 to September 1993). All but 2 of 6,912 registered polydactyly cases fit well into one of the following 11 preestablished polydactyly types (observed number of cases in parentheses): Postaxial hexadactyly (5,345), Preaxial-I hexadactyly (1,018), Seven or more digits (57), synpolydactyly (15), crossed polydactyly (45), 1st digit triphalangism (33), 2nd digit duplication (39), 3rd digit duplication (18), 4th digit duplication (22), Haas polysyndactyly (3), and high degree of duplication (4). The birth prevalence rates observed in both series were similar except for postaxial polydactyly, which was more frequent in the ECLAMC (150.2/100,000) than in the ECEMC (67.4/100,000), as expected due to the higher African Black ethnic extraction of the South-American than of the Spanish populations. This similar frequency for the rare polydactylies (5.4 per 100,000 in South America and 5.7 in Spain), and for each one of the 9 categories, suggests that the values reported here are valid for most populations. The rare polydactylies are frequently syndromal: one third of them (77/236) were found in association with other congenital anomalies, 11.0% (26/236) in MCA cases and 21.6% (51/236) in recognized syndromes.

The epidemiology of Down syndrome in four counties in Ireland 1981-1990

We conducted a descriptive epidemiological study of Down syndrome (DS) in the four Irish counties (Dublin, Kildare, Wicklow and Galway) covered by EUROCAT registries of congenital malformations for the years 1981-1990. EUROCAT registries, which cover defined populations, use multiple sources for case ascertainment. All DS cases born between 1 January 1981 and 31 December 1990 to mothers resident in the four counties were identified. Crude birth prevalence rates and maternal age-standardized rates (SPRs) were calculated for each county and for each year in the study period. The prevalence of DS by maternal age grouped in five-year periods and the risk for each five-year group were also estimated. The crude birth prevalence for the four counties was 18.5/10 000 for all births and 18.3 for live births. There was a fall in the total number of DS births over the decade, but less change in the crude birth prevalence owing to an increase in the proportion of mothers aged 35+. Galway had the highest crude birth prevalence of DS (23.5/10 000) but the SPR was within average for the four counties as a whole - 110.3, 95 per cent confidence interval (CI) 86.7-139. The risk of having a DS child increased 70-fold from 1:1841 at age 15-19 to 1:26 at 45 years or older. Nearly half of all DS cases (47.4 per cent) had at least one additional anomaly. The parts of Ireland covered by EUROCAT have a high birth prevalence of DS births as compared with some other countries, but the maternal age-specific rates are not substantially different from those in large international studies.

Limb reduction defects in South America.

Limb reduction defects were considered as possible indicators of environmental teratogenesis; it was suggested that also invasive prenatal procedures could increase the risk for limb reduction defects. The purpose of this work is to give a baseline frequency for limb reduction defects, using data from a population not exposed to prenatal diagnosis procedures. Using data collected in the period 1967 to 1992 within the frame of the Latin American Collaborative Study of Congenital Malformations which clinically examined 2,917,074 newborn infants, a total of 1715 with limb reduction defects were found. All cases were classified and analysed in 25 categories. Geographic differences in recorded rates were tested by chi 2 for homogeneity. Secular trends were analysed using chi 2 test for linear trends. The overall birth prevalence rate of limb reduction defects among liveborn infants was 4.91(per 10,000 births) (3.05 for isolated and 1.85 for associated cases). For stillbirths, the total prevalence was 26.73/10,000 (5.53 for isolated and 21.20 for associated cases). The inclusion of the brachydactylies increased those figures to 5.55/10,000 (3.39 for isolated and 2.16 for associated cases), and 27.42, respectively, (5.53 for isolated and 21.89 for associated cases). When isolated and associated cases were considered together, a geographic heterogeneity was found in pre-axial limb reduction defects; there was also some heterogeneity for amputations. A maternal age effect was found for the isolated hypoplasias. Standardising by maternal age, the overall prevalence of limb reduction in liveborn infants was 5.66 per 10,000 (95% CI = 5.38-5.93). An increasing trend was suggested by the isolated form of distal amputations which involved hands, feet, or digits. Our data suggest that clustering limb reduction defects in wide groups as transverse and longitudinal may lead to heterogeneous entities. When a possible association is suspected, it would be preferable to present and analyse data in the most discriminant form available. Due to the maternal age effect, it would be advisable to standardise the rates of transversal limb reduction defects by this variable.

Apparently normal frequency of congenital anomalies in the highly polluted town of Cubatão, Brazil.

Anencephaly is Suspected to cluster in the municipality of Cubatão (Brazil), and is attributed to industrial pollution. We surveyed malformations prospectively in 10,000 births, in 3 consecutive series, corresponding to 3 maternity hospital in Cubatão, under working definitions and norms taken from the ECLAMC (Latin American Collaborative Study of Congenital Malformations). The sample from Cubatão had a higher proportion of black racial ancestry, and lower frequencies for stillbirths and for immediate neonatal death, than in the rest of South America. The birth prevalence of malformations varied between the 3 hospitals in Cubatão, due to differences in ascertainment of minor defects. A higher-than-expected prevalence rate in Cubatão was observed only for postaxial polydactyly, probably due to a higher proportion of black racial ancestry, while lower-than-expected rates were obtained for congenital dislocation of the hip, and for babies with multiple congenital anomalies patterns, both of them attributed to underascertainment of minor defects. These observations do not support the suspicion of an elevated birth prevalence rate for anencephaly, neural tube defects, or any other major congenital malformation in Cubatão.

Universal screening for hemoglobinopathies using high-performance liquid chromatography: clinical results of 2.2 million screens.

In screening for hemoglobinopathies, high-performance liquid chromatography (HPLC) achieves excellent sensitivity and specificity, while adding the very important quantitative element to the analysis. Due to the development of a rapid, automated HPLC system, California began screening 600,000 births per year in 1990 using this method. Based on confirmatory testing for 97% of the initial positive results resulting from 2.2 million screens, HPLC has proven to be clinically accurate. In conjunction with the availability of quantitative data, HPLC provides a complete screening system, eliminating the need for a second screening test, and accurately discriminating beta thalassemia compound conditions. The large degree of ethnic diversity and high birth rate in California have produced detailed and reliable birth prevalence rates for most conditions and ethnicities.

Birth and population prevalence of Duchenne muscular dystrophy in the Netherlands

Mutations causing Duchenne muscular dystrophy (DMD) have a short survival. Therefore, birth and population prevalence are maintained by new mutations. The present inventory was made to estimate the birth and population prevalence rates of DMD in the Netherlands. Seven methods of case identification were used. Data on 496 definite, probable or possible DMD patients born since 1961, or alive on January 1, 1983, were obtained. Several methods gave an estimated ascertainment of more than 95%. The prevalence rate at birth of DMD was estimated at 23.7 x 10(-5) (1:4215) male live births (MLB) yearly. The prevalence rate in the male population on January 1, 1983 was 5.4 x 10(-5) (1:18496). About 1% of the males in this study may have autosomal recessive Duchenne-like muscular dystrophy. Until now there has been no convincing evidence for geographic differences in DMD prevalence at birth. A list of frequency studies of Duchenne muscular dystrophy is included. The DMD mutation rate calculated by the indirect method is 7.9 x 10(-5) genes per generation. However, this may well be an over-estimate, as this method does not account for germline mosaicism. Using a modified sex ratio method the proportion of sporadic DMD among all cases was estimated to be 0.106 (range 0-0.332). High frequency of germline mosaicism in DMD is a likely cause for the apparent lack of sporadic cases as found in previous studies, if mutation rates in male and female gametes are equal. Therefore, methods for estimating the proportion of new mutants in DMD should take germline mosaicism into account. The modified sex ratio method allows incorporation of data on germline mosaicism if available.

Timely monthly surveillance of birth prevalence rates of congenital malformations and genetic disorders ascertained by registries or other systematic data bases

In many jurisdictions large data sets on malformations are now collected routinely in order to define prevalence rates of malformations in infants and children, to detect long-term secular trends, and to ascertain cases for ad hoc case-control studies. With slight modifications, these data sets may be used for prompt surveillance of changes in the birth prevalence of malformations, changes that conceivably could be possibly due to the introduction of a teratogen into the environment. A specific logistic approach is suggested, modeled on the New York State Malformation Registry, for prompt detection of changes in rates.

Birth prevalence rates of skeletal dysplasias.

This study establishes the prevalence rates at birth of the skeletal dysplasias which can be diagnosed in the perinatal period or during pregnancy. Using a population-based register of congenital anomalies, a prevalence rate of 3.22 0/000 was observed. The most frequent types of skeletal dysplasia were achondroplasia and osteogenesis imperfecta (0.64 0/000, 1/15,000 births), thanatophoric dysplasia and achondrogenesis (0.28 0/000). The mutation rate for achondroplasia was higher in our material than in the other studies: 3.3 x 10(-5) per gamete per generation. Our study demonstrates that prenatal diagnosis by ultrasound is possible in some skeletal dysplasias.

The prevalence of cleft lip and palate in Japanese

To determine the prevalence of cleft lip and palate (CL/P) among the Japanese, 43 821 babies born between 1 January, 1985, and 31 December, 1985, were investigated. Sixty-four infants (0.146%) were found to demonstrate these abnormalities, a birth prevalence rate of 1.46/1000. Among 326 infants in whom it was possible to classify the types of cleft, born between 1 January, 1981, and 31 December, 1985, there were 111 (34.0%) with cleft lip (CL), 154 (47.3%) with cleft lip and palate (CLP) and 61 (18.7%) with cleft palate (CP).

Epidemiology of the early amnion rupture spectrum of defects.

We used data from the population-based Metropolitan Atlanta Congenital Defects Program to study the epidemiology of the early amnion rupture spectrum of defects. For the period 1968 through 1982, we identified 45 patients among 388,325 live births, for a birth prevalence rate of 1.16 per 10,000. The prevalence for male infants was 0.91 and for female infants, 1.44. The defects occurred 1.76 times more often in blacks than in whites (95% confidence interval 0.98, 3.13). Infants of young, black multigravidas (less than 20 years, more than one pregnancy) showed the highest rate (6.2), and infants of older, black multigravidas showed the lowest rate (0.5) (rate ratio = 12.4, 95% confidence interval 4.2, 36.4). These findings suggest that young, black multigravidas are at much higher risk than are older, black multigravidas of having infants with this spectrum of defects. Ascertainment (diagnostic) differences between hospitals probably account for some of the racial discrepancy in birth prevalence, but they do not explain the maternal age effects in black multigravidas. Because the higher rates for blacks probably reflect more accurate diagnoses, the findings also suggest that a closer estimate of the true birth prevalence may be about 3 per 10,000 live births.

The epidemiology of conjoined twins in Latin America.

Twenty-three cases of symmetrical conjoined twins were registered by the Latin-American Collaborative Study of Congenital Malformations (ECLAMC) in 1,714,952 births, which were observed during the 1967-1986 period in 95 maternity hospitals distributed in eleven Latin-American countries. This results in a birth prevalence rate of about 1/75,000 births. The secular and geographic distribution of this material do not depart from random in spite of one hospital with three cases, and two hospitals with two cases each, within a short time period. These 23 cases include one diprosopus, 3 dicephalus, one ischiopagus, 5 pygopagus, none dipygus, 3 syncephalus, none craniopagus, 9 thoracopagus, one omphalopagus, and one rachipagus. Sex distribution is even, with 12 male and 11 female cases.

Birth prevalence and mutation rate of achondroplasia in the Italian Multicentre Monitoring System for Birth Defects.

Achondroplasia (Acp) is one of the most common forms of osteochondrodysplasia (OCD). The clinical and radiological features of this condition are at present well known, while the frequency and mutation rate have been until now rarely studied. The old estimate reported by Morch (1) is somewhat overestimated as for the diagnostic criteria used (2) since some non-achondroplastic conditions are included (3). More recent estimates of the Acp birth prevalence have been reported by Gardner (4) Oberklaid et al. (5) and Orioli et al. (6).

CONGENITAL OCULAR BLINDNESS IN CHILDREN 1945 TO 1984

A total of 676 children born in British Columbia with congenital ocular blindness during the years 1945 through 1984 were studied. The birth prevalence rate of congenital blindness has decreased from eight per 10,000 live births in the late 1940s to three per 10,000 live births. Retinopathy of prematurity was replaced by genetic ocular disorders as the leading cause of congenital blindness, although the former is reemerging. The rate of congenital rubella infection also declined. There has been a significant increase in the rate of births with optic nerve lesions during the past 15 years, while the rate of births with lesions of the lens fell, reflecting the decline in the rate of maternal rubella infection. There are fewer children with congenital ocular legal blindness who have no light perception today, and they also have fewer associated handicaps.

Congenital ocular blindness in children, 1945 to 1984.

A total of 676 children born in British Columbia with congenital ocular blindness during the years 1945 through 1984 were studied. The birth prevalence rate of congenital blindness has decreased from eight per 10,000 live births in the late 1940s to three per 10,000 live births. Retinopathy of prematurity was replaced by genetic ocular disorders as the leading cause of congenital blindness, although the former is reemerging. The rate of congenital rubella infection also declined. There has been a significant increase in the rate of births with optic nerve lesions during the past 15 years, while the rate of births with lesions of the lens fell, reflecting the decline in the rate of maternal rubella infection. There are fewer children with congenital ocular legal blindness who have no light perception today, and they also have fewer associated handicaps.

Spina Bifida in Japan 1969‐1975: Geographical and Social Class Variations

Abstract An analysis of 1,103 fetal and postnatal deaths from spina bifida during 1969‐1975 is presented. The overall birth prevalence rate was 0.75 per 10,000 births and was slightly higher in the southwest than in the northeast of Japan. Social class variation in the prevalence rate during the period was studied. Geographical variation in the prevalence rate of spina bifida is not similar to that of anencephaly, whereas the social class variations in the prevalence rate of the two defects are similar.

Ethanol-sensitive times for the human conceptus.

The world's literature has been scoured to obtain data on 492 examples of the fetal alcohol syndrome (FAS) in the Northern Hemisphere. The seasonally pattern of FAS birth prevalence rates is compared with the seasonality pattern of ethanol intakes to estimate the time-lag between them and hence the timing of ethanol damage during development. It is tentatively suggested, in the light of the data, that this timing might be as late as the 18th-20th week. If this can be substantiated, it would alloy opportunities for preventive measures to be feasible even during pregnancy. Seasonality data have never previously been used to estimate the timing of a sensitive period in prenatal development. The present estimate for ethanol is, however, tentative and should be regarded only as an interesting indicator for future studies.

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 spine 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 spine 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 α-fetoprotein levels to detect neural tube defects.