Jorge S. Lopez-Camelo

Reduction of birth prevalence rates of neural tube defects after folic acid fortification in Chile

To verify whether the decreasing neural tube defects birth prevalence rates in Chile are due to folic acid fortification or to pre‐existing decreasing trends, we performed a population survey using a network of Estudio Colaborativo Latino Americano de Malformaciones Congénitas (ECLAMC, Latin American Collaborative Study of Congenital Malformations) maternity hospitals in Chile, between the years 1982 and 2002. Within each maternity hospital, birth prevalence rates of spina bifida and anencephaly were calculated from two pre‐fortification periods (1982–1989 and 1990–2000), and from one fortified period (2001–2002). There was no historical trend for spina bifida birth prevalence rates before folic acid fortification, and there was a 51% (minimum 27%, maximum 66%) decrease in the birth prevalence rates of this anomaly in the fortified period. The relative risks of spina bifida were homogeneous among hospitals in the two period comparisons. There was no historical trend for the birth prevalence of anencephaly comparing the two pre‐fortified periods, but the relative risks were heterogeneous among hospitals in this comparison. There was a 42% (minimum 10%, maximum 63%) decrease in the birth prevalence rate of anencephaly in the fortified period as compared with the immediately pre‐fortified period, with homogeneous relative risks among hospitals. Within the methodological constraints of this study we conclude that the birth prevalence rates for both spina bifida and anencephaly decreased as a result of folic acid fortification, without interference of decreasing secular trends.

Preliminary Data on Changes in Neural Tube Defect Prevalence Rates After Folic Acid Fortification in South America

Several South American countries are fortifying wheat flour with folic acid. However, only Chile started in 2000 to add 2.2 mg/kg, providing 360 μg daily per capita, an acceptable dosage for preventing the occurrence of some neural tube defect (NTD) cases. ECLAMC (Spanish acronym for the Latin American Collaborative Study of Congenital Malformations) routinely monitoring birth defects in South America since 1976, surveyed the impact of this fortification. Data from 361,374 births occurred in 43 South American hospitals, distributed in five different countries, active throughout the 1999–2001 triennium, were selected from the ECLAMC network. Birth prevalence rates for three different congenital anomalies with similar expected prevalence rates, were surveyed by the Cumulative Sum Method (CUSUM) method. They were NTD, oral clefts (OC), and Down syndrome (DS). Expected values were derived from observations made in 1999, and CUSUM was applied to the consecutive series of 24 months covering years 2000 and 2001. Only one of three congenital anomaly types, NTDs, in only one of five sampled out countries, Chile, showed a significant decrease, of 31%, during the 2000–2001 biennium, corresponding to the birth of the periconceptionally fortified infants. The level of significance (P < 0.001) was reached in the 20th month after fortification started, corresponding to August 2001. This is the first observation of a significant decrease in the occurrence of NTD after folic acid food fortification in a population little influenced by confounders common in the developed world as pre‐existing secular decreasing trends, and partially unregistered induced abortions.

Altitude as a risk factor for congenital anomalies

The birth prevalence of specific types of congenital anomalies at low and high altitudes in South America were compared after adjustment for prenatal growth, ethnicity, and socioeconomic status. The material includes all 1,668,722 consecutive births occurring in 53 hospitals participating in the Latin-American Collaborative Study of Congenital Malformations (ECLAMC), having registered at least 100 malformed/control pairs between 1967 and 1995. The lowland subsample (below 2,000 m above the sea level) included 46,729 case-control pairs, ascertained in 1,539,432 births from 49 hospitals in 38 cities. The highlands (above 2,000 m) comprised 3,498 case-control pairs from 129,301 births, occurring in four hospitals from three cities. Unconditional logistic regression was used to estimate the relative risks for the exposure at high altitudes, adjusted by ethnicity (Amerindian yes/no), type of health service (public/private), and birth weight (below/equal and greater than 2, 500 g). The adjusted relative risks showed significantly (P < 0.01) higher values in the high than in the lowlands for four types of defects: cleft lip [relative risks (RR): 1.57; 95% confidence interval (CI): 1.27-1.94], microtia (RR: 3.21; 95% CI: 2.35-4.79), preauricular tag (RR: 2.09; 95% CI: 1.86-2.36), branchial arch anomaly complex (RR: 1.79; 95% CI: 1.23-2.61), constriction band complex (RR: 1.92; 95% CI: 1.11-3.31), and anal atresia (RR: 1.61; 95% CI: 1.01-2.57). Conversely, lower risks in the highlands were registered for two neural tube defects: anencephaly (RR: 0.33; 95% CI: 0.20-0.54), spina bifida (RR: 0.57; 95% CI: 0.37-0.78), as well as for hydrocephaly (RR: 0.41; 95% CI: 0.22-0.77) and pes equinovarus (RR: 0.70; 95% CI: 0.51-0.96). Even though some of these differences may be caused by undetected confounders, the coincidental finding of four types of craniofacial defects with higher, and two types of neural tube defect with lower frequencies in the highlands, suggest a real biological foundation.

Folic acid flour fortification: Impact on the frequencies of 52 congenital anomaly types in three South American countries

The aim of the present investigation was to search for a reduction in birth prevalence estimates of 52 selected types of congenital anomalies, associated with folic acid fortification programs in Chile, Argentina, and Brazil. The material included 3,347,559 total births in 77 hospitals of the three countries during the 1982–2007 period: 596,704 births (17 hospitals) in Chile, 1,643,341 (41 hospitals) in Argentina, and 1,107,514 (19 hospitals) in Brazil. We compared pre‐ and post‐fortification rates within each hospital and the resulting Prevalence Rate Ratios (PRRs) were pooled by country. Statistically significant reductions in birth prevalence estimates after fortification were observed for neural tube defects (NTDs), septal heart defects, transverse limb deficiencies, and subluxation of the hip. However, only the reduction of NTDs appeared to be associated with folic acid fortification and not due to other factors, because of its consistency among the three countries, as well as with previously published reports, and its strong statistical significance. Among the NTDs, the maximum prevalence reduction was observed for isolated cephalic (cervical‐thoracic) spina bifida, followed by caudal (lumbo‐sacral) spina bifida, anencephaly, and cephalocele. This observation suggests etiologic and pathogenetic heterogeneity among different levels of spina bifida, as well as among different NTD subtypes. We concluded that food fortification with folic acid prevents NTDs but not other types of congenital anomalies.

Prenatal care effectiveness and utilization in Brazil

The impact of prenatal care use on birth outcomes has been understudied in South American countries. This study assessed the effects of various measures of prenatal care use on birth weight (BW) and gestational age outcomes using samples of infants born without and with common birth defects from Brazil, and evaluated the demand for prenatal care. Prenatal visits improved BW in the group without birth defects through increasing both fetal growth rate and gestational age, but prenatal care visits had an insignificant effect on BW in the group with birth defects when adjusting for gestational age. Prenatal care delay had no effects on BW in both infant groups but increased preterm birth risk in the group without birth defects. Inadequate care versus intermediate care also increased LBW risk in the group without birth effects. Quantile regression analyses revealed that prenatal care visits had larger effects at low compared with high BW quantiles. Several other prenatal factors and covariates such as multivitamin use and number of previous live births had significant effects on the studied outcomes. The number of prenatal care visits was significantly affected by several maternal health and fertility indicators. Significant geographic differences in utilization were observed as well. The study suggests that more frequent use of prenatal care can increase BW significantly in Brazil, especially among pregnancies that are uncomplicated with birth defects but that are at high risk for low birth weight. Further research is needed to understand the effects of prenatal care use for pregnancies that are complicated with birth defects.

Parental consanguinity in specific types of congenital anomalies.

Parental consanguinity, as a recognized risk factor for congenital anomalies, has mainly been studied with a focus on the types of parental relationships and their effects on genetic syndromes or birth defects in general. The present work analyzed the association between parental consanguinity and congenital anomalies, split, when possible, into clinical subtypes, in an attempt to obtain some insight into their recognized etiological heterogeneity. The material consisted of 34,102 newborn infants, affected by one of 47 selected congenital anomaly types, ascertained by the Latin-American Collaborative Study of Congenital Malformations (ECLAMC) during the period from 1967 to 1997. The consanguinity rate for each congenital anomaly type was compared with that of the population under study (0.96%), and the potentially confounding effect of six selected variables was controlled through a conditional logistic regression analysis for those congenital anomalies significantly associated with consanguinity. Pre-occurrence rates for the same congenital anomaly in sibships of consanguineous and non-consanguineous cases were compared. A significant association with parental consanguinity was observed for three congenital anomaly types: hydrocephalus, postaxial hand polydactyly, and bilateral cleft lip +/- cleft palate, while three additional anomalies, namely, cephalocele, microcephaly, and hand + foot postaxial polydactyly, showed a positive association, but statistical significance disappeared after adjustment for confounders, probably owing to sample size reduction. The association between consanguinity and Down syndrome was mainly due to the confounding effect of maternal age, while for hydrops fetalis and 2-3 toe syndactyly, the observed positive association could not be tested for confounders due to sample size reduction.

Heterogeneous rates for birth defects in Latin America: Hints on causality

The aim of this work was to disclose risk factors associated with birth defects which were heterogeneously distributed in the different geographic regions sampled by the Latin American Collaborative Study of Congenital Malformations (ECLAMC). The material included 2,159,065 hospital births, delivered in the 1967–1989 period in 24 geographic regions of Latin America. Birth defect types with 50 case‐control pairs or more were analyzed. A risk factor was defined as that available variable with differential geographic rates, correlated with those of a given birth defect type. Identified factors were tested by case‐control multivariate logistic regression to confirm their role in the occurrence of the defect. Altitude and maternal acute illness during first trimester of pregnancy, named influenza, were risk factors for microtia. Prenatal drug exposure, mainly sex hormones, were connected with the occurrence of hypospadias in low frequency areas, while Native ancestry was a “protective” factor in the same regions. Acute (influenza), and chronic (epilepsy and syphilis) maternal illness during first trimester of pregnancy and gravidity higher than four were risk factors for cleft lip. The independence of these variables from maternal age suggested that low maternal socioeconomic level could explain the high birth defect order and, perhaps, syphilis in mothers. Postaxial polydactyly was associated with parental consanguinity, as well as Afro‐American ancestry, suggesting genetic heterogeneity.

Regional analysis on the occurrence of oral clefts in South America.

The aim of this work was to search for unequal birth prevalence rates (BPRs) of cleft lip ± cleft palate (CL/P), and cleft palate only (CPO), among different geographic areas in South America, and to analyze phenotypic characteristics and associated risk factors in each identified cluster. Included were 5,128 CL/P cases, 1,745 CPO cases, and 3,712 controls (like‐sexed, non‐malformed liveborn infant, born immediately after a malformed one, in the same hospital), over 4,199,630 consecutive births. They were ascertained between 1967 and 2004, in 190 maternity hospitals of the ECLAMC (Estudio Colaborativo Latinoamericano de Malformaciones Congénitas) network, in 102 cities of all 10 South American countries. Non‐predefined geographical areas with significantly unusual cleft BPRs were identified with Kulldorf and Nagarwallas spatial scan statistic, employing number of cases and births, and exact location of each hospital. Expected values were cleft BPRs registered for the entire ECLAMC hospital network. Syndromic and non‐syndromic clefts were considered for cluster analysis, and phenotypic characterization, while only non‐syndromic for risk factor analysis. Seven clusters for CL/P, and four for CPO, with unusual BPRs were identified. CL/P cases in high BPR areas were more severe than elsewhere in the sample, similar to a previous ECLAMC report on microtia. For CL/P, high BPR clusters were associated with high altitude above sea level, Amerindian ancestry, and low socioeconomic strata; low BPR clusters showed association with African Black ancestry. Advanced maternal age, a recognized risk factor for CPO, was also associated with the only identified geographic cluster for CPO.

Preferential associations between oral clefts and other major congenital anomalies

Objectives: To identify preferential associations between oral clefts (CL  =  cleft lip only, CLP  =  cleft lip with cleft palate, CP  =  cleft palate) and nonoral cleft anomalies, to interpret them on clinical grounds, and, based on the patterns of associated defects, to establish whether CL and CLP are different conditions. Design And Settings: Included were 1416 cleft cases (CL  =  131, CLP  =  565, CP  =  720), among 8304 live- and stillborn infants with multiple congenital anomalies, from 6,559,028 births reported to the International Clearinghouse for Birth Defects Surveillance and Research by 15 registries between 1994 and 2004. Rates of associated anomalies were established, and multinomial logistic regressions applied to identify significant associations. Results: Positive associations with clefts were observed for only a few defects, among which anencephaly, encephaloceles, club feet, and ear anomalies were the most outstanding. Anomalies negatively associated with clefts included congenital heart defects, VATER complex (vertebral defects, imperforate anus, tracheoesophageal fistula, and radial and renal dysplasia), and spina bifida. Conclusion: The strong association between all types of clefts and anencephaly seems to be attributable to cases with disruptions; the association between CP and club feet seems to be attributable to conditions with fetal akinesia. Some negative associations may depend on methodologic factors, while others, such as clefts with VATER components or clefts with spina bifida, may depend on biological factors. The different patterns of defects associated with CL and CLP, indicating different underlying mechanisms, suggest that CL and CLP reflect more than just variable degrees of severity, and that distinct pathways might be involved.

Early exposure to yellow fever vaccine during pregnancy

Objective  To investigate the association of Yellow Fever Vaccination (YFV) during pregnancy with the presence of structural defect in exposed babies.