Ascertainment of pregnancies terminated because of birth defects: effect on completeness of adding a new source of data

BACKGROUND: When evaluating preventive programs such as folate promotion and rubella vaccination, it is critically important to include terminations of pregnancy for neural tube defects and congenital rubella syndrome. Data from birth defects registries are often used for this purpose. The Western Australian Birth Defects Registry ascertains cases of birth defects in livebirths, stillbirths, and terminations of pregnancy for fetal abnormality, using multiple sources of ascertainment. METHODS: Data on terminations of pregnancy for fetal abnormality from the Western Australian Hospital Morbidity Data System 1980-1997 (not previously available to the Registry) were used to estimate the completeness of ascertainment of such cases by the Registry. Ascertainment-adjusted prevalences were calculated using capture-recapture methods. RESULTS: A total of 702 terminations with birth defects were identified among hospital discharges, most of which were already known to the Registry (87.9%). Of the 85 new cases, seven had a neural tube defect, 23 had a chromosomal defect, and 12 had confirmed maternal rubella infection during pregnancy. The ascertainment-adjusted prevalence was not importantly [corrected] different for birth defects overall or for these individual conditions, although the 95% confidence intervals for all birth defects, and for all chromosomal defects, did not include the prevalence based on registered cases only. CONCLUSIONS: The Western Australian Birth Defects Registry ascertains a high proportion of pregnancies terminated for fetal abnormality, and should therefore be a reliable source of data with which to assist in monitoring the effectiveness of preventive programs.     

Maternal obesity and morbid obesity: The risk for birth defects in the offspring

BACKGROUND : The objective of this study was to assess, in a large data set from Swedish Medical Health Registries, whether maternal obesity and maternal morbid obesity were associated with an increased risk for various structural birth defects. METHODS : The study population consisted of 1,049,582 infants born in Sweden from January 1, 1995, through December 31, 2007, with known maternal weight and height data. Women were grouped in six categories of body mass index (BMI) according to World Health Organization classification. Infants with congenital birth defects were identified from three sources: the Swedish Medical Birth Registry, the Register of Birth Defects, and the National Patient Register. Maternal age, parity, smoking, and year of birth were thought to be potential confounders and were included as covariates in the adjusted odds ratio analyses. RESULTS : Ten percent of the study population was obese. Morbid obesity (BMI ≥ 40) occurred in 0.7%. The prevalence of congenital malformations was 4.7%, and the prevalence of relatively severe malformations was 3.2%. Maternal prepregnancy morbid obesity was associated with neural tube defects OR 4.08 (95% CI 1.87–7.75), cardiac defects OR 1.49 (95% CI 1.24–1.80), and orofacial clefts OR 1.90 (95% CI 1.27–2.86). Maternal obesity (BMI ≥ 30) significantly increased the risk of hydrocephaly, anal atresia, hypospadias, cystic kidney, pes equinovarus, omphalocele, and diaphragmatic hernia. CONCLUSION : The risk for a morbidly obese pregnant woman to have an infant with a congenital birth defect is small, but for society the association is important in the light of the ongoing obesity epidemic. Birth Defects Research (Part A), 2010. © 2009 Wiley‐Liss, Inc.     

Time trends in the prevalence of birth defects in Texas 1999–2007: Real or artifactual?

BACKGROUND: Few studies have reported time trends for total birth defects or for a comprehensive range of phenotypes. METHODS: We examined data from the Texas Birth Defects Registry (TBDR) from 1999 through 2007. Poisson regression was used to fit trend lines to birth prevalence over time for total birth defects (each infant/fetus counted once), for every birth defect collected by the TBDR, and for subsets of cases or defects grouped various ways. RESULTS: From 1999 through 2007, birth prevalence of total birth defects in Texas increased 3.6% per year. Increases were observed in all population groups, persisted after adjustment for demographic characteristics, and were strongest in regions of Texas that were more urban. There was a wide variety of different defects showing significant increases. The trends of several defects were driven by their mild cases. Perhaps the most compelling finding was that larger upward trends were observed in defects that had been rated as more susceptible to diagnostic variation. One notable exception to that was gastroschisis, which showed an average increase of over 5% per year, the total birth defects rate in TBDR increased at 3.6% per year, similar to 3.7% per year in birth certificate check boxes. CONCLUSIONS: In our opinion, the weight of evidence in our study suggests that the observed increase over time in total birth defects and in many specific birth defects is artifactual. This likely reflects increased awareness, referral, detection, or documentation in health care facilities visited by TBDR staff, resulting in more complete ascertainment by the registry, rather than a true change over time in the occurrence of most birth defects. Birth Defects Research (Part A), 2011. © 2011 Wiley‐Liss, Inc.     

Are there ethnic disparities in risk of preterm birth among infants born with congenital heart defects?

BACKGROUND: Birth defects and preterm birth (PTB) are leading causes of infant morbidity and mortality in the United States. Infants with birth defects are more likely to be born preterm (<37 weeks), yet the roles of maternal ethnicity and fetal growth in this relationship are unclear. This study aimed to assess the risk of PTB among non-Hispanic (NH) Black, NH-White, and Hispanic infants with congenital heart defects (CHD), adjusting for fetal growth. METHODS: Florida Birth Defects Registry data were used to conduct a retrospective cohort study on 14,319 live-born infants with CHDs born January 1, 1998 to December 31, 2002. ORs and 95% CIs were computed for each growth category (small-for-gestational age [SGA], appropriate-for-gestational-age [AGA], and large-for-gestational-age [LGA]) by ethnicity and adjusted for maternal and infant covariates using logistic regression. RESULTS: After adjusting for potential confounders, SGA and AGA NH-Black infants with CHDs had increased risk of PTB compared to NH-White infants with CHDs (OR 1.79; 95% CI: 1.40, 2.30 and OR 1.89; 95% CI: 1.68, 2.13, respectively). Hispanic SGA, AGA, and infants with CHDs had no increased risk of PTB compared to NH-White infants. CONCLUSIONS: The increased risk of PTB among SGA and AGA NH-Black infants with CHDs is not explained by the overall disparities in risk of PTB between NH-Blacks and NH-Whites. Additional studies are needed to determine the specific subtypes of CHD for which these relationships are present and if these findings are seen among infants with other birth defects.     

Using registry data to suggest which birth defects may be more susceptible to artifactual clusters and trends

BACKGROUND: Some birth defects appear to be more susceptible than others to artifactual prevalence variability over time or geographically. This article uses an empirical approach to try to identify them. METHODS: Assumption: Variation in clinical practice and other artifactual sources of variability impact observed variation in prevalence of mild cases more than severe cases for a given birth defect. Approach: Data were examined from Texas Birth Defects Registry deliveries from 1999-2003. For each of 312 delivery hospitals, birth prevalence for mild cases was calculated for birth defect X. The 5(th) percentile was subtracted from the 95(th) percentile to measure spread in the frequency distribution of all hospitals. That was repeated for severe cases. The ratio of the mild:severe spread was calculated for 49 defects, and the defects ranked into quintiles. That was repeated using birth prevalence based on county, and using isolated cases. The percentages of severe cases were calculated and also ranked into quintiles. A sensitivity analysis and simulation were conducted. RESULTS: Forty-nine birth defects were ranked from those least susceptible to differences in mild:severe prevalence variability (e.g., anencephaly, hypoplastic left heart syndrome) to most susceptible (e.g., atrial septal defect, fetal alcohol syndrome). Resulting quintile ranks based on the three measures were highly correlated, whether based on all cases or isolated cases. CONCLUSIONS: This empirical approach may be helpful for a number of public health applications. Birth defects and other health outcomes more susceptible to prevalence variability may be more likely to exhibit artifactual trends or clusters.     

Maternal occupational exposure to ionizing radiation and birth defects

So far, only a few studies investigated occupational exposure to ionizing radiation in pregnancy to cause birth defects (BDs). No association between BDs and ionizing radiation, although described for high-dose exposure, could ever be confirmed for employees, or specific job titles. Here, an explorative analysis of a prospective population-based birth cohort used to quantify the prevalence of BDs in infants between 1/2007 and 2/2008 is presented. An active examination of all livebirths by specially trained paediatricians in two defined areas was performed. Additionally, a study-specific questionnaire distributed among all becoming mothers in the surveyed regions included questions on maternal occupational exposure to ionizing radiation within the first trimester of pregnancy. In 3,816 births (including 165 infants with BDs; 4.3%), maternal answers concerning possible exposures to medical and occupational ionizing radiation were available. Relative risk (RR) estimates in mothers surveyed for occupational exposure to ionizing radiation (wearing a radiation dosimeter) and BDs in the offspring were calculated exploratively. A higher prevalence of infants with BDs (n = 4; 13.8%) was documented in newborns of the 29 surveyed mothers compared to that in 3,787 births from unexposed mothers (n = 161; 4.3%), corresponding to a RR of 3.2 (1.2–8.7). Excluding deformations, the RR increased to 4.0 (1.5–10.7). Adjustment for possible confounders did not change the results substantially.     

Prevalence of down syndrome among children and adolescents in metropolitan Atlanta

BACKGROUND: Down syndrome (DS) prevalence estimates beyond infancy are needed to assess health service needs among those with DS. METHODS: Children with DS born in metropolitan Atlanta from 1979 through 2003 were ascertained from a population-based birth defects registry. Vital status through 2003 was obtained using case records, vital records, and the National Death Index. Prevalence was calculated by dividing the children surviving with DS by the population derived from U.S. Census estimates. Variations in DS prevalence by race, heart defects, age, birth cohort, and time period were examined using Poisson regression. RESULTS: In metropolitan Atlanta in 2003, there were 67 livebirths with DS (13.0 per 10,000 livebirths) and 738 0- to 19-year-olds surviving with DS (8.3 per 10,000 population). Over time, births to mothers 35 years and older and DS birth prevalence increased. Birth prevalence was higher among Whites, did not vary by sex, and was higher for infants without heart defects. DS prevalence among 0- to 14-year-olds increased over time (p < .05). Within each 5 year birth cohort, prevalence decreased with age: this decrease was greater among Blacks than among Whites and among children with heart defects than among children without heart defects. CONCLUSIONS: DS prevalence increased among livebirths and among young children. Further studies are warranted to determine whether health services are meeting the needs of an increasing number of children with DS.     

Changes in the birth prevalence of selected birth defects after grain fortification with folic acid in the United States: findings from a multi-state population-based study

BACKGROUND: Observational studies and clinical trials have suggested that periconceptional use of folic acid can reduce the risk of birth defects other than neural tube defects (NTDs). Using data reported by states to the National Birth Defects Prevention Network, we examined whether folic acid fortification might have decreased the prevalence of other specific birth defects. METHODS: For each of 16 birth defect categories selected for study, birth prevalence for two time periods was calculated with data submitted from a number of states in 1995-1996 ("pre-fortification") and 1999-2000 ("post-fortification"). Changes in birth prevalence between the two time periods were assessed by calculating prevalence ratios and 95% confidence intervals for each defect, and compared by maternal race/ethnicity and availability of prenatally diagnosed cases. RESULTS: We confirmed previously reported reductions in the birth prevalence of NTDs. In addition, we found modest, yet statistically significant, decreases in the birth prevalence for transposition of the great arteries(12%), cleft palate only (12%), pyloric stenosis (5%), upper limb reduction defects (11%), and omphalocele (21%). More substantial subgroup decreases were observed for renal agenesis among programs that conduct prenatal surveillance (28%), for common truncus among Hispanics (45%), and for upper limb reduction defects among Hispanics (44%). There were modest yet significant increases in the prevalence of obstructive genitourinary defects (12%) and Down syndrome (7%), but not among programs conducting prenatal surveillance for these defects. CONCLUSIONS: These results suggest some modest benefit from the folic acid fortification on the prevalence of a number of non-NTD birth defects.     

Medications used to treat nausea and vomiting of pregnancy and the risk of selected birth defects

BACKGROUND Nausea and vomiting of pregnancy (NVP) occurs in up to 80% of pregnant women, but its association with birth outcomes is not clear. Several medications are used for the treatment of NVP; however, data are limited on their possible associations with birth defects. METHODS Using data from the National Birth Defects Prevention Study (NBDPS)—a multi‐site, population‐based, case‐control study—we examined whether NVP or its treatment was associated with the most common noncardiac defects in the NBDPS (nonsyndromic cleft lip with or without cleft palate [CL/P], cleft palate alone [CP], neural tube defects, and hypospadias) compared with randomly selected nonmalformed live births. RESULTS Among the 4524 cases and 5859 controls included in this study, 67.1% reported first‐trimester NVP, and 15.4% of them reported using at least one agent for NVP. Nausea and vomiting of pregnancy was not associated with CP or neural tube defects, but modest risk reductions were observed for CL/P (adjusted odds ratio [aOR] = 0.87; 95% confidence interval [CI], 0.77–0.98) and hypospadias (aOR = 0.84; 95% CI, 0.72–0.98). Regarding treatments for NVP in the first trimester, the following adjusted associations were observed with an increased risk: proton pump inhibitors and hypospadias (aOR = 4.36; 95% CI, 1.21–15.81), steroids and hypospadias (aOR = 2.87; 95% CI, 1.03–7.97), and ondansetron and CP (aOR = 2.37; 95% CI, 1.18–4.76), whereas antacids were associated with a reduced risk for CL/P (aOR = 0.58; 95% CI, 0.38–0.89). CONCLUSIONS NVP was not observed to be associated with an increased risk of birth defects; however, possible risks related to three treatments (i.e., proton pump inhibitors, steroids and ondansetron), which could be chance findings, warrant further investigation. Birth Defects Research (Part A) 2012. © 2011 Wiley Periodicals, Inc.     

Maternal caffeine intake during pregnancy and orofacial clefts

BACKGROUND: Moderate caffeine intake during pregnancy is common, but little is known about its potential association with birth defects. METHODS: The National Birth Defects Prevention Study is a population‐based, case‐control study of major birth defects, excluding infants with single‐gene disorders and chromosomal abnormalities. This analysis includes infants with cleft lip with or without cleft palate (CL/P) and cleft palate only (CPO), excluding infants whose cleft was secondary to holoprosencephaly or amniotic band sequence. Mothers reported dietary caffeine intake from coffee, tea, sodas, and chocolate in the year before pregnancy and reported intake of medications containing caffeine during pregnancy. We assessed the association between dietary caffeine intake, frequency of consuming each type of caffeinated beverage, medications containing caffeine, and CL/P or CPO among infants born from October 1997 through December 2004. RESULTS: This analysis included 1531 infants with CL/P, 813 infants with CPO, and 5711 infants with no major birth defects (controls). Examining dietary sources among control mothers, 11% reported consuming at least 300 mg of caffeine per day and 17% reported consuming less than 10 mg of caffeine per day; high consumption (≥3 servings per day) was reported by 8% (coffee), 4% (tea), and 15% (sodas); medications containing at least 100 mg caffeine/dose were reported by less than 1%. Although some effect estimates were elevated for moderate caffeine intake from all beverages, estimates were closer to the null for high caffeine levels. Isolated CL/P was associated with use of medications containing at least 100 mg of caffeine per dose. CONCLUSIONS: Our data do not suggest an association between maternal dietary caffeine intake and orofacial clefts, but caffeine‐containing medications merit further study. Birth Defects Research (Part A), 2009. © 2009 Wiley‐Liss, Inc.     

Determinants of survival in children with congenital abnormalities: a long-term population-based cohort study

BACKGROUND: Today more children with birth defects survive early childhood because of improved medical care; however, little information is available about patterns of long-term mortality and survival in this population. In particular, it is not clear whether other birth characteristics, apart from birth defects, have any role in their mortality. METHODS: Two large cohorts of children with and without birth defects were followed for up to 17 years. More than 45,000 children with birth defects, and 45,000 matched children without birth defects born in Ontario between 1979 and 1986 were followed. Throughout the study period long-term survival rates and the risk of death were compared between the 2 cohorts. Birth characteristics were also examined to determine their effect on the risk of death. RESULTS: During the study the deaths of 3620 and 301 children with and without birth defects, respectively, were recorded, indicating that those with birth defects had a 13 times higher rate of mortality (relative risk [RR], 12.9, 95% confidence interval [CI], 12.1-13.7). Mortality rates in the birth-defects cohort remained higher even after 10-15 years. In both groups children of low gestational age and low birth weight had a higher risk of death. There was a strong dose-response relationship between the number of defects and the risk of death. CONCLUSIONS: Children born with abnormalities face many challenges throughout their lifetimes. If they survive the high mortality risk of the first year of life, they still have to face the considerably higher risk of death in the years to come. In addition to birth defects, other birth characteristics play an independent role in their mortality. These indicators could be used to identify high-risk children.     

Epidemiology of nonsyndromic conotruncal heart defects in Texas, 1999-2004

INTRODUCTION: Congenital heart defects (CHDs) are the most common structural birth defects, yet their etiology is poorly understood. As there is heterogeneity within the group of CHDs, epidemiologic studies often focus on subgroups, of conditions, such as conotruncal heart defects (CTDs). However, even within these subgroups there may be etiologic heterogeneity. The aim of the present study was to identify and compare maternal and infant characteristics associated with three CTDs: truncus arteriosus (TA), dextro‐transposition of the great arteries (d‐TGA), and tetralogy of Fallot (TOF). METHODS: Data for cases with nonsyndromic TA (n = 78), d‐TGA (n = 438), and TOF (n = 529) from the Texas Birth Defects Registry, 1999–2004, were used to estimate crude and adjusted prevalence ratios, separately for each condition, using Poisson regression. Polytomous logistic regression was used to determine whether the observed associations were similar across the two largest case groups (d‐TGA and TOF). RESULTS: In Texas, 1999–2004, the prevalence of nonsyndromic TA, d‐TGA, and TOF was 0.35, 1.98, and 2.40 per 10,000 live births, respectively. There was evidence of a significant linear increase in the risk of each condition with advancing maternal age (p < 0.01). Significant associations were observed for TA and maternal residence on the Texas‐Mexico border; d‐TGA and infant sex, maternal race/ethnicity, history of previous live birth, and birth year; and TOF and maternal race/ethnicity and education. Further, the associations with some, but not all, of the study variables were significantly different for d‐TGA and TOF. CONCLUSION: These findings add to our limited understanding of the epidemiology of CTDs. Birth Defects Research (Part A), 2010. © 2010 Wiley‐Liss, Inc.     

Maternal panic disorder and congenital abnormalities: a population-based case-control study

BACKGROUND: Maternal panic disorder in pregnancy is the most common manifestation of anxiety disorders in Hungary. The association between panic disorder during pregnancy and structural birth defects, i.e., congenital abnormalities, was studied. METHODS: The prevalence of maternal panic disorder in cases with different congenital abnormalities was compared to that of matched controls in the population-based Hungarian Case-Control Surveillance System of Congenital Abnormalities. RESULTS: Of 22,843 cases with congenital abnormalities, 210 (0.9%) had mothers with panic disorder during pregnancy compared to 187 (0.5%) of 38,151 controls (adjusted prevalence odds ratio [POR] 1.6; 95% CI, 1.3-2.0). Specific groups of congenital abnormalities were also assessed versus controls. Cases with isolated cleft lip with or without cleft palate (CL/P) (adjusted POR, 3.4; 95% CI, 1.3-9.0) and multiple congenital abnormalities (adjusted POR, 3.0; 95% CI, 1.2-7.2) were more likely to have had mothers with panic disorder during the study pregnancy. Notably, among mothers with panic disorders, the associations were found only in offspring of untreated mothers. CONCLUSIONS: A higher rate of isolated CL/P and multiple congenital abnormalities may be caused by the direct biological effect of panic disorder or by the interaction of maternal panic disorder and lifestyle factors. Antipanic drug treatment seems to have a protective effect for isolated CL/P and multiple congenital abnormalities. Birth Defects Research (Part A), 2006.     

Pregnancy outcomes following systemic prenatal acyclovir exposure: Conclusions from the international acyclovir pregnancy registry, 1984-1999

BACKGROUND: Oral acyclovir is commonly used for genital herpes and other herpesvirus infections. Data on potential fetal risk are extremely limited. From 1984 to 1998, the Acyclovir in Pregnancy Registry monitored birth outcomes of women exposed to oral or intravenous acyclovir during pregnancy. This report describes the final results. METHODS: The registry was publicized to health care providers most likely to diagnose pregnancy; providers called the registry telephone number, then mailed in a brief questionnaire. Pregnancy outcomes were categorized either as outcomes with birth defects or outcomes without birth defects, subcategorized as live births, spontaneous pregnancy losses (including stillbirths), and induced abortions. Birth defects were defined using a modification of the CDC definition for birth defects surveillance systems. Observed rates were compared to the rate (3.2%) of birth defects expected in the general population. RESULTS: Between June 1, 1984 and June 30, 1998, 1695 pregnancies exposed to oral or IV acyclovir were registered; 461 (27%) were lost to follow-up. A total of 1234 pregnancies in 24 countries were followed, with a total of 1246 outcomes. Among 1246 pregnancy outcomes, 756 involved acyclovir exposure in the first trimester, 197 in the second trimester, and 291 in the third trimester. Among live births with first trimester acyclovir exposure, risk of birth defects was 19 of 596 (3.2%; 95% CI, 2.0-5.0%). No unusual defects or pattern of defects were apparent. CONCLUSIONS: The observed rates and types of birth defects for pregnancies exposed to acyclovir did not differ significantly from those in the general population. Birth Defects Research (Part A), 2004. Published 2004 Wiley-Liss, Inc.     

Cancer Risk in Children and Adolescents with Birth Defects: A Population-Based Cohort Study

Objective

Birth defects are an increasing health priority worldwide, and the subject of a major 2010 World Health Assembly Resolution. Excess cancer risk may be an added burden in this vulnerable group of children, but studies to date have provided inconsistent findings. This study assessed the risk for cancer in children and young adolescents with major birth defects.

Methods and Findings

This retrospective, statewide, population-based, cohort study was conducted in three US states (Utah, Arizona, Iowa). A cohort of 44,151 children and young adolescents (0 through 14 years of age) with selected major, non-chromosomal birth defects or chromosomal anomalies was compared to a reference cohort of 147,940 children without birth defects randomly sampled from each state’s births and frequency matched by year of birth. The primary outcome was rate of cancer prior to age 15 years, by type of cancer and type of birth defect. The incidence of cancer was increased 2.9-fold (95% CI, 2.3 to 3.7) in children with birth defects (123 cases of cancer) compared to the reference cohort; the incidence rates were 33.8 and 11.7 per 100,000 person-years, respectively. However, the excess risk varied markedly by type of birth defect. Increased risks were seen in children with microcephaly, cleft palate, and selected eye, cardiac, and renal defects. Cancer risk was not increased with many common birth defects, including hypospadias, cleft lip with or without cleft palate, or hydrocephalus.

Conclusion

Children with some structural, non-chromosomal birth defects, but not others, have a moderately increased risk for childhood cancer. Information on such selective risk can promote more effective clinical evaluation, counseling, and research.     

Increase in the Prevalence of Obesity in Switzerland 1982–2007: Birth Cohort Analysis Puts Recent Slowdown into Perspective

Although the prevalence of obesity continues to increase in Switzerland, the latest figures suggest a slowdown in the rate of increase. In order to elucidate whether this could be the onset of a trend reversal, we analyzed cross‐sectional data by birth cohort. We assessed the prevalence of overweight+ (BMI ≥25 kg/m²) and obesity (BMI ≥30 kg/m²) in six population surveys with self‐reported height and weight values (Switzerland, N = 68,829, 1982–2007, men (45%) and women (55%), aged 20–84 years) by 10‐year birth cohorts (from the decade 1910–1919 through to 1970–1979). We found that increases in the prevalence of overweight+ and obesity occurred mainly in the cohort born 1930 to 1939, and again in the cohorts born 1960 to 1979. The accelerated increase in the prevalence of overweight+ in the youngest birth cohort and the lower prevalence in the oldest birth cohorts suggest that the current slowdown seen in Switzerland may not herald the onset of a trend reversal. As this example shows, simple comparisons of prevalence rates over time could provide a misleading picture of actual trends. Birth cohort analysis may offer a valuable alternative.     

Extremely high prevalence of neural tube defects in a 4-county area in Shanxi Province, China

BACKGROUND: In the past, northern China's Shanxi Province has reported the highest incidence of neural tube defects (NTDs) in the world. However, little is known about the epidemiology of NTDs in this area in recent years. METHODS: Data were collected from a population-based birth defects surveillance system in 4 counties that captures information on all live births, stillbirths of at least 20 weeks' gestation, and pregnancy terminations at any gestational age resulting from prenatal diagnosis of a birth defect. We also surveyed mothers of NTD case patients to determine their use of folic acid before and during early pregnancy. RESULTS: During 2003, 160 NTD cases were identified among 11,534 births (NTD birth prevalence = 138.7/10,000 births). The rates of anencephaly, spina bifida and encephalocele were 65.9, 58.1, and 14.7 per 10,000, respectively, and a female predominance was observed among anencephaly cases (male-to-female relative risk [RR], 0.49; 95% confidence interval [CI], 0.30-0.79), but not among spina bifida (RR, 0.90; 95% CI, 0.55-1.45) and encephalocele (RR, 1.03; 95% CI, 0.40-2.69) cases. The percentages of pregnancy termination following prenatal diagnosis of anencephaly, spina bifida, and encephalocele were 50%, 41.8%, and 35.3%, respectively. NTD birth prevalence tended to be higher among mothers aged <20 or > or =30 years (P = .06) and was markedly associated with lower levels of maternal education (P < .001). Among 143 NTD mothers, only 6 (4.2%) used folic acid supplements during the periconceptional period. CONCLUSIONS: The NTD birth prevalence rate in the study area is among the highest worldwide. Folic acid deficiency may be one important risk factor.     

Sex differences in birth defects: a study of opposite-sex twins

BACKGROUND: Sex differences in structural birth defects are often confounded by environmental risk factors. Opposite-sex twins provide a unique model for detecting sex differences in birth defects while maximally controlling environmental risk factors in a natural setting. METHODS: Population data from the Florida Birth Defects Registry were analyzed. A total of 4,768 pairs of twins who were discordant for sex and born between 1996 and 2001 were analyzed. The McNemar test was used to compare the differences between a male twin and his twin sister for the risk of developing specific defects and organ-system defects. RESULTS: Of 4,768 twin pairs, 225 males (4.72%) and 175 females (3.67%) had birth defects. Among opposite-sex twin pairs, males had a 29% higher risk for birth defects than their twin sisters. Compared to their twin sisters, males had a 5.4 times higher risk for pyloric stenosis and a 2.4 times higher risk for obstructive genitourinary defect, but only one-tenth the risk for congenital hip dislocation. CONCLUSIONS: Sex differences in birth defects exist between opposite-sex twins.