Risk factors in the origin of congenital left-ventricular outflow-tract obstruction defects of the heart: a population-based case-control study

Systematic Review and Meta-analysis of Prenatal Risk Factors for Congenital Heart Disease: Maternal Chronic Diseases and Parental Exposures

BACKGROUND

There is considerable heterogeneity in studies on prenatal risk factors for congenital heart diseases (CHDs). We performed a meta-analysis of all nongenetic factors of CHDs. This report presents results of factors related to maternal chronic diseases and parental exposures.

METHODS

A systematic search encompassing concepts of CHD and risk factors was used, using the following inclusion criteria: (1) original peer-reviewed articles, (2) quantifying the effects of risk factors for CHDs, (3) between 1989 and 2022. Pooled odds ratios (ORs) and 95% confidence interval (CI) were calculated using a random-effect model.

RESULTS

Inclusion criteria were met for 170 studies. There was an association between being overweight or obese and CHDs (OR, 1.26; 95% CI, 1.15-1.37), with a dose-effect relationship. Pregestational diabetes (PGDM) was associated with CHDs (OR, 3.51; 95% CI, 2.86-4.3), without difference between type 1 and type 2 PGDM. The effect size of gestational diabetes was less than that of PGDM (OR, 1.38; 95% CI, 1.18-1.61). There was an association between CHDs and pre-eclampsia (OR, 2.01; 95% CI, 1.32-3.05), paternal smoking (OR, 1.32; 95% CI, 1.03-1.70), and alcohol use (OR, 1.50; 95% CI, 1.08-2.08). A smaller association was found with maternal smoking and advanced maternal age.

CONCLUSIONS

There exists robust evidence for increased risk of CHD in the presence of obesity, maternal diabetes, maternal smoking, and increased maternal age. The effect sizes were relatively modest, except for PGDM. The robustness of the evidence decreased when CHDs were divided into subgroups or when the analyses were restricted to severe CHDs.

Uncovering the Hidden Dangers and Molecular Mechanisms of Excess Folate: A Narrative Review

This review delves into the intricate relationship between excess folate (vitamin B9) intake, especially its synthetic form, namely, folic acid, and its implications on health and disease. While folate plays a pivotal role in the one-carbon cycle, which is essential for DNA synthesis, repair, and methylation, concerns arise about its excessive intake. The literature underscores potential deleterious effects, such as an increased risk of carcinogenesis; disruption in DNA methylation; and impacts on embryogenesis, pregnancy outcomes, neurodevelopment, and disease risk. Notably, these consequences stretch beyond the immediate effects, potentially influencing future generations through epigenetic reprogramming. The molecular mechanisms underlying these effects were examined, including altered one-carbon metabolism, the accumulation of unmetabolized folic acid, vitamin-B12-dependent mechanisms, altered methylation patterns, and interactions with critical receptors and signaling pathways. Furthermore, differences in the effects and mechanisms mediated by folic acid compared with natural folate are highlighted. Given the widespread folic acid supplementation, it is imperative to further research its optimal intake levels and the molecular pathways impacted by its excessive intake, ensuring the health and well-being of the global population.

The association between folic acid supplementation and congenital heart defects: Systematic review and meta-analysis

Introduction:

Various trial and epidemiological studies consistently documented the association between maternal folic acid supplementations and neural tube defects. However, existing literatures revealed inconclusive findings about maternal periconceptional folic acid supplementations and the risk of congenital heart defects. Thus, the current systematic review and meta-analysis was aimed to estimate the pooled association between maternal periconceptional folic acid supplementations and congenital heart defects.

Methods:

Electronic searches of PubMed, Web of Science/Scopus, Cochrane library and Google Scholar databases were conducted to access the required studies published up to March 2021. Predetermined eligibility criteria were used for study selections. Data extraction were independently done on excel. STATA version 14 software was used to calculate the pooled effect size with 95% confidence intervals (95% CI) of maternal periconceptional folic acid supplementations on congenital heart defects using the DerSimonian and Laird random effects meta-analysis (random effects model). Statistical heterogeneity was checked using the Cochran Q test (chi-squared statistic), I2 statistic, and by visual inspection of the funnel plot.

Results:

A total of 37 studies of case–control, cohort and randomized controlled trial in nature were included in the review. The finding of the present systematic review and meta-analysis indicated that periconceptional folic acid supplementation significantly decreases the risk of congenital heart defects (risk ratio (RR), 0.79; CI, 0.71, 0.89). Both Cochrane Q test statistic (χ2 = 19.33, p = 0.962) and I2 test statistic (I2 = 0.0%, p = 0.962) did not reveal statistically significant heterogeneity among included studies. In this meta-analysis, traditional funnel plot, Begg’s funnel plot, Egger’s weighted regression (p = 0.13) as well as Begg’s rank correlation statistic (p = 0.676) revealed no evidence of publication bias.

Conclusion:

The present systematic review and meta-analysis found that maternal periconception folic acid supplementation was significantly associated with the risk of congenital heart defects. The risk of congenital heart defects was significantly reduced by 21% among those children of mothers who use periconceptional folic acid supplementations in high-income countries. We recommend that a large prospective study be conducted to investigate the association between maternal periconceptional folic acid supplementation and occurrence of congenital heart defect of various types, especially in the developing countries.

Risks of specific congenital anomalies in offspring of women with diabetes: A systematic review and meta-analysis of population-based studies including over 80 million births

BACKGROUND

Pre-gestational diabetes mellitus (PGDM) has been known to be a risk factor for congenital heart defects (CHDs) for decades. However, the associations between maternal PGDM and gestational diabetes mellitus (GDM) and the risk of specific types of CHDs and congenital anomalies (CAs) in other systems remain under debate. We aimed to investigate type-specific CAs in offspring of women with diabetes and to examine the extent to which types of maternal diabetes are associated with increased risk of CAs in offspring.

METHODS AND FINDINGS

We searched PubMed and Embase from database inception to 15 October 2021 for population-based studies reporting on type-specific CAs in offspring born to women with PGDM (combined type 1 and 2) or GDM, with no limitation on language. Reviewers extracted data for relevant outcomes and performed random effects meta-analyses, subgroup analyses, and multivariable meta-regression. Risk of bias appraisal was performed using the Cochrane Risk of Bias Tool. This study was registered in PROSPERO (CRD42021229217). Primary outcomes were overall CAs and CHDs. Secondary outcomes were type-specific CAs. Overall, 59 population-based studies published from 1990 to 2021 with 80,437,056 participants met the inclusion criteria. Of the participants, 2,407,862 (3.0%) women had PGDM and 2,353,205 (2.9%) women had GDM. The meta-analyses showed increased risks of overall CAs/CHDs in offspring born to women with PGDM (for overall CAs, relative risk [RR] = 1.99, 95% CI 1.82 to 2.17, P < 0.001; for CHDs, RR = 3.46, 95% CI 2.77 to 4.32, P < 0.001) or GDM (for overall CAs, RR = 1.18, 95% CI 1.13 to 1.23, P < 0.001; for CHDs, RR = 1.50, 95% CI 1.38 to 1.64, P < 0.001). The results of the meta-regression analyses showed significant differences in RRs of CAs/CHDs in PGDM versus GDM (all P < 0.001). Of the 23 CA categories, excluding CHD-related categories, in offspring, maternal PGDM was associated with a significantly increased risk of CAs in 21 categories; the corresponding RRs ranged from 1.57 (for hypospadias, 95% CI 1.22 to 2.02) to 18.18 (for holoprosencephaly, 95% CI 4.03 to 82.06). Maternal GDM was associated with a small but significant increase in the risk of CAs in 9 categories; the corresponding RRs ranged from 1.14 (for limb reduction, 95% CI 1.06 to 1.23) to 5.70 (for heterotaxia, 95% CI 1.09 to 29.92). The main limitation of our analysis is that some high significant heterogeneity still persisted in both subgroup and sensitivity analyses.

CONCLUSIONS

In this study, we observed an increased rate of CAs in offspring of women with diabetes and noted the differences for PGDM versus GDM. The RRs of overall CAs and CHDs in offspring of women with PGDM were higher than those in offspring of women with GDM. Screening for diabetes in pregnant women may enable better glycemic control, and may enable identification of offspring at risk for CAs.

Maternal sociodemographic characteristics, early pregnancy behaviours, and livebirth outcomes as congenital heart defects risk factors - Northern Ireland 2010-2014

BACKGROUND

Congenital Heart Defects (CHD) is the most commonly occurring congenital anomaly in Europe and a major paediatric health care concern. Investigations are needed to enable identification of CHD risk factors as studies have given conflicting results. This study aim was to identify maternal sociodemographic characteristics, behaviours, and birth outcomes as risk factors for CHD. This was a population based, data linkage cohort study using anonymised data from Northern Ireland (NI) covering the period 2010-2014. The study cohort composed of 94,067 live births with an outcome of 1162 cases of CHD using the International Statistical Classification of Diseases and Related Health Problems (ICD)-10 codes and based on the European Surveillance of Congenital Anomalies (EUROCAT) grouping system for CHD. CHD cases were obtained from the HeartSuite database (HSD) at the Royal Belfast Hospital for Sick Children (RBHSC), maternal data were extracted from the Northern Ireland Maternity System (NIMATS), and medication data were extracted from the Enhanced Prescribing Database (EPD). STATA version 14 was used for the statistical analysis in this study, Odds Ratio (OR), 95% Confident intervals (CI), P value, and logistic regression were used in the analysis. Ethical approval was granted from the National Health Service (NHS) Research Ethics Committee.

RESULT

In this study, a number of potential risk factors were assessed for statistically significant association with CHD, however only certain risk factors demonstrated a statistically significant association with CHD which included: gestational age at first booking (AOR = 1.21; 95% CI = 1.04-1.41; P < 0.05), family history of CHD or congenital abnormalities and syndromes (AOR = 4.14; 95% CI = 2.47-6.96; P < 0.05), woman's smoking in pregnancy (AOR = 1.22; 95% CI = 1.04-1.43; P < 0.05), preterm birth (AOR = 3.01; 95% CI = 2.44-3.01; P < 0.05), multiple births (AOR = 1.89; 95% CI = 1.58-2.60; P < 0.05), history of abortion (AOR = 1.12; 95% CI = 1.03-1.28; P < 0.05), small for gestational age (SGA) (AOR = 1.44; 95% CI = 1.22-1.78; P < 0.05), and low birth weight (LBW) (AOR = 3.10; 95% CI = 2.22-3.55; P < 0.05). Prescriptions and redemptions of antidiabetic (AOR = 2.68; 95% CI = 1.85-3.98; P < 0.05), antiepileptic (AOR = 1.77; 95% CI = 1.10-2.81; P < 0.05), and dihydrofolate reductase inhibitors (DHFRI) (AOR = 2.13; 95% CI = 1.17-5.85; P < 0.05) in early pregnancy also showed evidence of statistically significant association with CHD.

CONCLUSION

The results of this study suggested that there are certain maternal sociodemographic characteristics, behaviours and birth outcomes that are statistically significantly associated with higher risk of CHD. Appropriate prevention policy to target groups with higher risk for CHD may help to reduce CHD prevalence. These results are important for policy makers, obstetricians, cardiologists, paediatricians, midwives and the public.

Comprehensive assessment of the associations between maternal diabetes and structural birth defects in offspring: a phenome-wide association study

PURPOSE

Our objective was to comprehensively evaluate the risk of a broad range of birth defects among offspring of women with diabetes, overall and stratified by pregestational versus gestational diagnosis, using the phenome-wide association (PheWAS) methodology.

METHODS

We performed a registry linkage study of all live births (>6,500,000) and birth defects cases (>290,000) in Texas, 1999-2015. We ascertained diabetes from birth and fetal death certificates. We calculated prevalence rate ratios (PRR) for phenotypes with ≥10 cases among exposed offspring (n = 130).

RESULTS

Diabetes was associated with the prevalence of any defect (PRR 1.40, 95% confidence interval [CI] 1.38-1.42), multiple defects (PRR 1.86, 95% CI 1.81-1.91), and 60 specific phenotypes, including novel (hypospadias, mitral stenosis) and previously reported phenotypes (renal a-/dysgenesis, spinal anomalies). Pregestational diabetes was a stronger risk factor for any defect (PRR 2.00, 95% CI 1.93-2.07), multiple defects (PRR 3.27, 95% CI 3.11-3.44), and the 60 specific phenotypes evaluated. Gestational diabetes was associated with any defect (PRR 1.21, 95% CI 1.19-1.23) and 47 specific birth defects phenotypes, although associations were weaker than for pregestational diabetes.

CONCLUSIONS

The PheWAS is an efficient way to identify risk factors for disease using population-based registry data. Pregestational diabetes is associated with a broader range of phenotypes than previously reported. Because diabetes is diagnosed in 1% of women prior to pregnancy and 6%-9% during pregnancy, our results highlight a significant public health concern.

Risk of congenital heart defects in offspring exposed to maternal diabetes mellitus: an updated systematic review and meta-analysis

PURPOSE

A systematic review and meta-analysis was performed to assess the risk of congenital heart defects (CHDs) and its specific phenotypes associated with maternal diabetes mellitus (DM) including pregestational diabetes mellitus (PGDM) and gestational diabetes mellitus (GDM).

METHODS

PubMed, Embase, Medline, Google Scholar, Cochrane Libraries, China National Knowledge Infrastructure, Wanfang Database, Chinese Scientific Journals Fulltext Database and China Biology Medicine disc were searched from the inception dates to 15 December 2018, to identify case-control or cohort studies assessing the association between maternal DM and risk of CHDs. The exposure of interest was maternal DM; the outcomes of interest were CHDs and its specific phenotypes. Either a fixed- or a random-effects model was used to calculate the overall combined risk estimates. Subgroup analyses were performed to explore potential heterogeneity moderators.

RESULTS

Total 52 studies, which involved 259,917 patients with CHDs among 16,929,835 participants, were included for analysis. Overall, mothers with DM compared with those without DM had a significantly higher risk of CHDs in offspring [odds ratios (OR) = 2.71, 95% confidence intervals (CI) 2.28-3.23]. When data were restricted to different types of DM, a significantly increased risk of CHDs was observed among mothers with PGDM (OR = 3.18, 95% CI 2.77-3.65) and GDM (OR = 1.98, 95% CI 1.66-2.36). Our study suggested the risk of CHDs was significantly higher among mothers with PGDM than those with GDM. Additionally, this study suggested maternal DM was significantly associated with most phenotypes of CHDs; of these, double outlet of the right ventricle (OR = 10.89; 95% CI 8.77-13.53), atrioventricular septal defect (OR = 5.74; 95% CI 3.20-10.27) and truncus arteriosus (OR = 5.06; 95% CI 2.65-9.65) were identified as the first three of the most common phenotypes of CHDs associated with maternal DM.

CONCLUSIONS

The maternal DM including PGDM and GDM are significantly associated with risk of CHDs and its most phenotypes. The PGDM seems to be more likely to cause CHDs in offspring than GDM. Further studies are needed to clarify the underlying mechanisms.

Maternal folic acid supplementation and dietary folate intake and congenital heart defects

Background

It has been reported that folic acid supplementation before and/or during pregnancy could reduce the risk of congenital heart defects (CHDs). However, the results from limited epidemiologic studies have been inconclusive. We investigated the associations between maternal folic acid supplementation, dietary folate intake, and the risk of CHDs.

Methods

A birth cohort study was conducted in 2010–2012 at the Gansu Provincial Maternity & Child Care Hospital in Lanzhou, China. After exclusion of stillbirths and multiple births, a total of 94 births were identified with congenital heart defects, and 9,993 births without any birth defects. Unconditional logistic regression was used to estimate the associations.

Results

Compared to non-users, folic acid supplement users before pregnancy had a reduced risk of overall CHDs (OR: 0.42, 95% CI: 0.21–0.86, P_trend = 0.025) after adjusted for potential confounders. A protective effect was observed for certain subtypes of CHDs (OR: 0.37, 95% CI: 0.16–0.85 for malformation of great arteries; 0.26, 0.10–0.68 for malformation of cardiac septa; 0.34, 0.13–0.93 for Atrial septal defect). A similar protective effect was also seen for multiple CHDs (OR: 0.49, 95% CI: 0.26–0.93, P_trend = 0.004). Compared with the middle quartiles of dietary folate intake, lower dietary folate intake (<149.88 μg/day) during pregnancy were associated with increased risk of overall CHDs (OR: 1.63, 95% CI: 1.01–2.62) and patent ductus arteriosus (OR: 1.85, 95% CI: 1.03–3.32). Women who were non-user folic acid supplement and lower dietary folate intake have almost 2-fold increased CHDs risk in their offspring.

Conclusions

Our study suggested that folic acid supplementation before pregnancy was associated with a reduced risk of CHDs, lower dietary folate intake during pregnancy was associated with increased risk. The observed associations varied by CHD subtypes. A synergistic effect of dietary folate intake and folic acid supplementation was also observed.

The impact of folic acid supplementation on gestational and long term health: Critical temporal windows, benefits and risks

Highlights

Associations between FA supplementation in pregnancy and effects on offspring's NTDs, allergy/respiratory problems, cancer and behaviour problems as been studied.There is growing concern about the effects of excessive FA supplementation, whether in terms of doses or times of exposure.FA supplementation in the periconceptional period is protective against NTDs while in later periods it could be deleterious.A daily dose of 0.4 mg FA in the periconceptional period seems to be effective and safe.

Abstract

Maternal folic acid (FA) supplementation is one of the most popular nutritional interventions during pregnancy for its protective effect against neural tube defects (NTDs).The purposes of this review are: (a) to gather the current evidence regarding supplementation of maternal diet with FA and (b) to problematize the available literature in terms of dosages, critical temporal windows, and its potential benefits and risks.The expression (pregnancy OR fetus OR offspring OR mother) AND ("folic acid" AND supplementation) was searched on PubMed database, filtering for articles published from 2005 to 2014. Publications referring to FA supplementation during the periconceptional period or pregnancy in which there was a conclusion about the effects of isolated FA supplementation on pregnant woman, pregnancy or offspring were included. Of the initial 1182 papers, 109 fulfilled the inclusion criteria.The majority of the publications reported FA supplementation outcomes on offspring's health, with emphasis in NTDs, allergy/respiratory problems, cancer and behaviour problems. Some inconsistency is observed on the impact of FA supplementation on different outcomes, except for NTDs. It is also visible an increased concern about the impact of excessive supplementation, either in terms of doses or exposure's duration.In conclusion, there is a growing interest in FA supplementation issues. The protective effect of FA supplementation over NTDs has been confirmed, being the periconceptional period a critical window, and it is frequently suggested that allergy/respiratory outcomes arise from (excessive) FA supplementation particularly later in pregnancy. Further research on critical doses and time of exposure should be conducted.

Genome-Wide DNA Methylation Analysis and Epigenetic Variations Associated with Congenital Aortic Valve Stenosis (AVS)

Congenital heart defect (CHD) is the most common cause of death from congenital anomaly. Among several candidate epigenetic mechanisms, DNA methylation may play an important role in the etiology of CHDs. We conducted a genome-wide DNA methylation analysis using an Illumina Infinium 450k human methylation assay in a cohort of 24 newborns who had aortic valve stenosis (AVS), with gestational-age matched controls. The study identified significantly-altered CpG methylation at 59 sites in 52 genes in AVS subjects as compared to controls (either hypermethylated or demethylated). Gene Ontology analysis identified biological processes and functions for these genes including positive regulation of receptor-mediated endocytosis. Consistent with prior clinical data, the molecular function categories as determined using DAVID identified low-density lipoprotein receptor binding, lipoprotein receptor binding and identical protein binding to be over-represented in the AVS group. A significant epigenetic change in the APOA5 and PCSK9 genes known to be involved in AVS was also observed. A large number CpG methylation sites individually demonstrated good to excellent diagnostic accuracy for the prediction of AVS status, thus raising possibility of molecular screening markers for this disorder. Using epigenetic analysis we were able to identify genes significantly involved in the pathogenesis of AVS.

A genome-wide association study of congenital cardiovascular left-sided lesions shows association with a locus on chromosome 20

Congenital heart defects involving left-sided lesions (LSLs) are relatively common birth defects with substantial morbidity and mortality. Previous studies have suggested a high heritability with a complex genetic architecture, such that only a few LSL loci have been identified. We performed a genome-wide case-control association study to address the role of common variants using a discovery cohort of 778 cases and 2756 controls. We identified a genome-wide significant association mapping to a 200 kb region on chromosome 20q11 [P= 1.72 × 10^-8 for rs3746446; imputed Single Nucleotide Polymorphism (SNP) rs6088703 P= 3.01 × 10^-9, odds ratio (OR)= 1.6 for both]. This result was supported by transmission disequilibrium analyses using a subset of 541 case families (lowest P in region= 4.51 × 10^-5, OR= 1.5). Replication in a cohort of 367 LSL cases and 5159 controls showed nominal association (P= 0.03 for rs3746446) resulting in P= 9.49 × 10^-9 for rs3746446 upon meta-analysis of the combined cohorts. In addition, a group of seven SNPs on chromosome 1q21.3 met threshold for suggestive association (lowest P= 9.35 × 10^-7 for rs12045807). Both regions include genes involved in cardiac development-MYH7B/miR499A on chromosome 20 and CTSK, CTSS and ARNT on chromosome 1. Genome-wide heritability analysis using case-control genotyped SNPs suggested that the mean heritability of LSLs attributable to common variants is moderately high ([Formula: see text] range= 0.26-0.34) and consistent with previous assertions. These results provide evidence for the role of common variation in LSLs, proffer new genes as potential biological candidates, and give further insight to the complex genetic architecture of congenital heart disease.

Maternal folic acid supplementation and the risk of congenital heart defects in offspring: a meta-analysis of epidemiological observational studies

Epidemiological studies have reported conflicting results regarding the association between maternal folic acid supplementation and the risk of congenital heart defects (CHDs). However, a meta-analysis of the association between maternal folic acid supplementation and CHDs in offspring has not been conducted. We searched the MEDLINE and EMBASE databases for articles cataloged between their inceptions and October 10, 2014 and identified relevant published studies that assessed the association between maternal folate supplementation and the risk of CHDs. Study-specific relative risk estimates were pooled using random-effects or fixed-effects models. Out of the 1,606 articles found in our initial literature searches, a total of 1 randomized controlled trial, 1 cohort study, and 16 case-control studies were included in our final meta-analysis. The overall results of this meta-analysis provide evidence that maternal folate supplementation is associated with a significantly decreased risk of CHDs (RR = 0.72, 95% CI: 0.63–0.82). Statistically significant heterogeneity was detected (Q = 82.48, P < 0.001, I² = 79.4%). We conducted stratified and meta-regression analyses to identify the origin of the heterogeneity among the studies, and a Galbraith plot was generated to graphically assess the sources of heterogeneity. This meta-analysis provides a robust estimate of the positive association between maternal folate supplementation and a decreased risk of CHDs.

Cardiovascular management in pregnancy: congenital heart disease

The population of adults with CHD continues to expand,and thus the number of women with CHD who contemplate pregnancy or become pregnant is also growing. Mothers with low-risk defects can be managed by general cardiologist,whereas those with more complex defects should be managed by or with the assistance of ACHD cardiologists. It is important to acknowledge that all patients with CHD may have unique anatomy or physiology, despite their classification as having a simple, moderate, or complex defect. As such, clinicians evaluating these patients should have adequate knowledge and expertise when assessing patient's risk for pregnancy,when performing imaging or hemodynamic studies, and when managing these patients during pregnancy. The American Board of Medical Specialties has recently recognized ACHD as a subspecialty of cardiovascular disease to treat the specialized needs of these patients in adulthood. ACHD experts can provide expertise in the management of specific defects or lesions, imaging techniques, prepregnancy risk assessment,and can manage these patients or comanage them with other medical providers during their pregnancy. Because many of these ACHD patients are lost to follow-up in adulthood, pregnancy represents a time when these patients seek medical care(and for some, represents a time of vulnerability and increased risk). This represents an opportunity to establish or reestablish care with ACHD specialists and to reestablish continuing long-term care for their CHD. Pregnancy also provides an opportunity to create partnerships between primary care physicians,adult cardiologists, and ACHD specialists to provide optimal care for these women throughout their lives.

Risk of birth defects associated with maternal pregestational diabetes

Maternal diabetes preceding pregnancy may increase the risk of birth defects in the offspring, but not all studies confirm this association, which has shown considerable variation over time, and the effect of having type 1 versus type 2 diabetes is unclear. We conducted a population-based cohort study in the Northern Italy Emilia-Romagna region linking administrative databases with a Birth Defects Registry. From hospital discharge records we identified all diabetic pregnancies during 1997-2010, and a population of non-diabetic parturients matched for age, residence, year and delivery hospital. We collected available information on education, smoking and drug prescriptions, from which we inferred the type of diabetes. We found 62 malformed infants out of 2,269 births among diabetic women, and 162 out of 10,648 births among non-diabetic women. The age-standardized prevalence ratio (PR) of malformation associated with maternal pregestational diabetes was 1.79 (95 % confidence interval 1.34-2.39), a value that varied little by age. Type of diabetes strongly influenced the PR, with higher values related to type 2 diabetic women. Most major subgroups of anomalies had PRs above 1, including cardiovascular, genitourinary, musculoskeletal, and chromosomal abnormalities. There was an unusually high PR for the rare defect 'extra-ribs', but it was based on only two cases. This study indicates that maternal pregestational type 2 diabetes is associated with a higher prevalence of specific birth defects in offspring, whereas for type 1 diabetic mothers, particularly in recent years, the association was unremarkable.