Surveillance of birth defects is important for identifying patterns in prevalence and potential risk factors. Birth defects occur among 3% of births, and are one of the leading causes of infant mortality in the United States.¹ The causes of 65%–80% of birth defects are unknown²; however, certain risk factors have been linked with abnormal fetal development.³ Using data from birth defects surveillance systems, research studies may identify these risk factors, resulting in preventative action to decrease the occurrence of specific birth defects (for example, using folic acid supplementation to reduce the incidence of neural tube defects).^3,4 Birth defect surveillance systems have been essential in comparing the prevalence of neural tube defects before and after fortification of enriched cereal grains with folic acid in the United States, and in identifying ethnic and racial disparities, resulting in targeted preconception folic acid awareness campaigns.⁴

In 2003, the New Hampshire Birth Conditions Program (NHBCP) was created. The NHBCP is a population-based, active case ascertainment surveillance system that monitors the occurrence of 45 birth defects among all newborns, stillborns, terminated fetuses (no gestational age limit), and infants up to 2 years of age. Although strict procedures are in place for protecting privacy and data confidentiality, a 2008 law (New Hampshire RSA 141:J) was passed requiring implementation of a new opt-out procedure that allows individuals the option to have identifiable information removed from the NHBCP database. This law applies to data collected from January 1, 2007 onwards. The purpose of this study was to assess the effects of the implementation of the opt-out legislation on data collection by the NHBCP and the surveillance of birth defects in New Hampshire.

For the period 2007–2009, 776 infants were identified for inclusion by the NHBCP, of whom 120 (15.5%) fell into the DIIR group. Among the mothers of Hispanic and “other” ethnicities, larger proportions (33% and 29%, respectively) were in the DIIR group when compared to non-Hispanic white mothers at 15% (Table 1). For the different age categories, the largest proportion of mothers who were in the DIIR group were those younger than 25 years of age (Table 1). No significant differences by infant year of birth were observed; however, the higher number of birth defect cases among the DIIR group during the initial implementation of the law most likely was due to delayed mailings and, hence, a higher proportion of undeliverable opt-out packages (Table 1). Although there were no statistically significant differences by payer source, of those with private insurance, only 12% were in the DIIR group; whereas, of those with Medicaid or who self-paid, 20% and 19% (respectively) were in the DIIR group (Table 1). No substantial differences by birth outcome, county of residence (Table 1), or birth defect diagnoses (Table 2) were observed.

Results from this study demonstrated that certain factors could be associated with a family’s willingness to have their identifiable information included in a birth defect surveillance system. Key differences in some sociodemographic characteristics existed between the IIR group, consisting of families who did not choose to opt out of the NHBCP surveillance system, and the DIIR group, consisting of those who either did choose to opt out or were treated as opt-out birth defect cases because the mailed opt-out package was not deliverable. There were significant differences in infant race/ethnicity and maternal age at delivery, suggesting that there might have been socioeconomic differences influencing the decision to opt out, or that younger mothers and those of Hispanic ethnicity might have been more transient and harder to reach via mail. In a study that examined characteristics between mothers who had a baby born with a birth defect who either consented or did not consent to follow-up, significant differences were also observed by race and maternal age; however, these differences disappeared after adjustment for perinatal mortality.⁵ Although not statistically significant, in the current study, the differences observed by payer source, a proxy for socioeconomic status, also suggests that there might have been notable socioeconomic differences between the IIR and DIIR groups, as a greater proportion of those with Medicaid or who self-paid were more likely to opt out or have the opt-out package be undeliverable.

Within the DIIR group, we were not able to distinguish between the parents who chose to have their identifiable information removed from those parents who were considered to have opted out due to an undeliverable mail package as the reason why a case is in the DIIR group is not included in the NHBCP database. As a result, we were not able to assess differences between these 2 subgroups. Fortunately, the NHBCP is required to remove only identifiable information for the DIIR group regardless of whether the parent chose to opt out or the mail was undeliverable; if all data were to be removed for true opt-outs, for those classified as having opted out because of undeliverable mail, or for both of these sub-groups, there would be a considerable impact on accurate surveillance as prevalence rates for specific birth defects would be affected. Incomplete case inclusion in a given region would result in distorted prevalence estimates, resulting, in turn, in underestimation of the health care service needs of infants born with specific birth conditions.³ Additionally, differences in birth defect occurrence between the 2 opt-out groups could affect the accuracy and usefulness of the birth defect surveillance system; however, there did not appear to be substantial differences in the proportion of specific birth defects between the 2 groups. As it stands, the lack of identifiable information in the NHBCP will affect research studies if long-term follow-up is required, or if geospatial analysis is to be conducted for birth defect cluster analysis.⁶ Fortunately, researchers are still able to link infant records with maternal and paternal records; therefore, most risk factors for birth defects can be assessed in future studies.³

Public health surveillance is critical for monitoring diseases or conditions for their prevalence, potential risk factors, and health service requirements.⁷ To ensure appropriate evidence-based activities are created, complete and accurate surveillance data are necessary.⁸ Birth defects surveillance systems have access to data sources containing individual, health-related information under public health authority; however, as data protection and security concerns are increasing, state legislatures can mandate additional reporting guidelines and procedures.^6,8 Privacy concerns and their effects on accurate surveillance are national issues, and not unique to New Hampshire.⁷ As is the case in New Hampshire, if opt-out procedures are mandated by law, it will be critical to improve these procedures to ensure surveillance is maximized for optimal public health benefit.