Birth Defects Cluster Study: a national approach to birth defects cluster investigations

A multidisciplinary and structured investigation of three suspected clusters of transverse upper limb reduction defects in France

INTRODUCTION

Between 2019-2021, facing public concern, a scientific expert committee (SEC) reanalysed suspected clusters of transverse upper limb reduction defects (TULRD) in three administrative areas in France, where initial investigations had not identified any risk exposure. We share here the national approach we developed for managing suspicious clusters of the same group of congenital anomalies occurring in several areas.

METHODS

The SEC analysed the medical records of TURLD suspected cases and performed spatiotemporal analyses on confirmed cases. If the cluster was statistically significant and included at least three cases, the SEC reviewed exposures obtained from questionnaires, environmental databases, and a survey among farmers living near to cases' homes concerning their plant product use.

RESULTS

After case re-ascertainment, no statistically significant cluster was observed in the first administrative areas. In the second area, a cluster of four children born in two nearby towns over two years was confirmed, but as with the initial investigations, no exposure to a known risk factor explaining the number of cases in excess was identified. In the third area, a cluster including just two cases born the same year in the same town was confirmed.

DISCUSSION

Our experience highlights that in the event of suspicious clusters occurring in different areas of a country, a coordinated and standardised approach should be preferred.

Evidence for a cluster of rare birth defects in the Ain department (France)

BACKGROUND

REMERA (REgistre des Malformations En Rhône-Alpes) is a registry of congenital malformations that covers 58,000 births annually in Central-East France. In 2010, the registry raised an alarm to the health authorities (Santé publique France, SpF) about three cases of a unilateral isolated transverse upper limb reduction defect (UITULRD) in a small subarea; the general prevalence of this defect is one case in 10,000 births. In the following years, more infants were born with the same malformation in the same territory of the Ain department. Public health authorities, supported by an expert committee, rejected the existence of a cluster, but we aim here at providing evidence for this cluster.

METHODS

Geocoded data for all UITULRD cases (ICD-10 codes Q71.2 and Q71.3) were extracted from the REMERA database. We conducted a Kulldorff cluster analysis of these data, using the spatial SaTScanTM algorithm.

RESULTS

The analysis found a cluster of eight cases of UITULRD among the 8,204 births occurring between 2009 and 2014 within a circle of 16.24 km radius centered on a village of the Ain department, whereas 0.82 cases were expected under a uniform probability of such a birth throughout the registry territory. This represents an almost 10fold excess over the expected number of cases (p = .0057).

CONCLUSIONS

The arguments used to deny the cluster are disputed and we present the evidence supporting its reality. The controversy that has followed the alarm has compromised the search for the cause(s) of this excess of rare malformations.

Evaluating geostatistical modeling of exceedance probability as the first step in disease cluster investigations: very low birth weights near toxic Texas sites

BACKGROUND

The first step in evaluating potential geographic clusters of disease calls for an evaluation of the disease risk comparing the risk in a defined location to the risk in neighboring locations. Environmental exposures, however, represent continuous exposure levels across space not an exposure with a distinct boundary. The objectives of the current study were to adapt, apply and evaluate a geostatistical approach for identifying disease clusters.

METHODS

The exceedance probability for very low birth weight (VLBW; < 1.5 kg) infants was mapped using an Intrinsic Conditional Autoregressive model. The data were applied to a 20 by 20 grid of 1 km2 pixels centered on each of the 13 National Priority List Superfund Sites in Harris County, Texas.

RESULTS

Large clusters of VLBW were identified in close proximity to four of the 13 Superfund Sites. Three of the Superfund Sites, associated with disease clusters, were located close together in central Houston and these sites may have been surrounded by a single, confluent disease cluster.

CONCLUSIONS

Geostatistical modeling of the exceedance probability for very low birth weights identified disease clusters of varying size, shape and statistical certainty near Superfund Sites in Harris County, Texas. The approach offers considerable potential as the first step for investigating potential disease clusters.

Prevalence and correlates of gastroschisis in 15 states, 1995 to 2005

OBJECTIVE

To identify trends in the prevalence and epidemiologic correlates of gastroschisis using a large population-based sample with cases identified by the National Birth Defects Prevention Network over the course of an 11-year period.

METHODS

This study examined 4,713 cases of gastroschisis occurring in 15 states during 1995-2005, using public use natality data sets for denominators. Multivariable Poisson regression was used to identify statistically significant risk factors, and Joinpoint regression analyses were conducted to assess temporal trends in gastroschisis prevalence by maternal age and race and ethnicity.

RESULTS

Results show an increasing temporal trend for gastroschisis (from 2.32 per 10,000 to 4.42 per 10,000 live births). Increasing prevalence of gastroschisis has occurred primarily among younger mothers (11.45 per 10,000 live births among mothers younger than age 20 years compared with 5.35 per 10,000 among women aged 20 to 24 years). In the multivariable analysis, using non-Hispanic whites as the referent group, non-Hispanic black women had the lowest risk of having a gastroschisis-affected pregnancy (prevalence ratio 0.42, 95% confidence interval [CI] 0.37-0.48), followed by Hispanics (prevalence ratio 0.86, 95% CI 0.81-0.92). Gastroschisis prevalence did not differ by newborn sex.

CONCLUSIONS

Our findings demonstrate that the prevalence of gastroschisis has been increasing since 1995 among 15 states in the United States, and that higher rates of gastroschisis are associated with non-Hispanic white maternal race and ethnicity, and maternal age younger than 25 years (particularly younger than 20 years of age).

LEVEL OF EVIDENCE

III.

Maternal and child health epidemic-assistance investigations, 1946-2005

In this article, the authors focus on epidemic-assistance investigations that dealt with maternal and child health problems, including unintended and adolescent pregnancy and family planning; international reproductive health surveys among refugees; pregnancy outcomes, including abortion, maternal mortality, infant mortality, and birth defects; leukemia; and Reye syndrome. During 1946-2005, a total of 1,969 investigations had sufficient data to classify them as possibly related to maternal and child health and were characterized by distinctive periods. Those related to family planning, pregnancy intention, and reproductive health among refugees began in the early 1970s and continued through 2005. Abortion-related investigations occurred during 1971-1982. Investigations of non-abortion-related maternal morbidity and mortality began in 1979 and included 2 international epidemic-assistance investigations. Investigations of clusters of disease among infants began in the 1960s, with a special focus on Reye syndrome during 1964-1984. Investigations of childhood cancer and birth defects began in the late 1950s. The Centers for Disease Control and Prevention has used the epidemic-assistance investigations mechanism to respond to a wide range of health concerns of women and children. The investigations of abortion-related health problems might have had the best-documented impact on public policy and public health.