Elsevier

Annals of Epidemiology

Volume 26, Issue 4, April 2016, Pages 267-274
Annals of Epidemiology

Original article
Population impact of preterm birth and low birth weight on developmental disabilities in US children

https://doi.org/10.1016/j.annepidem.2016.02.012Get rights and content

Abstract

Purpose

Although previous studies demonstrate associations between adverse perinatal outcomes and developmental disabilities (DDs), study of population impacts is limited.

Methods

We computed relative risks adjusted (aRRs) for sociodemographic factors and component and summary population attributable fractions (PAFs) for associations between very low birth weight (VLBW, all preterm births), moderately low birth weight (MLBW) + Preterm, MLBW at term, and normal birth weight (NBW) + Preterm and seven DDs (cerebral palsy [CP], autism spectrum disorder [ASD], intellectual disability [ID], behavioral-conduct disorders, attention-deficit-hyperactivity disorder [ADHD], learning disability [LD], and other developmental delay) among children aged 3–17 years in the 2011–2012 National Survey of Children's Health.

Results

VLBW-Preterm, MLBW-Preterm and NBW-Preterm were strongly to moderately associated with CP (aRRs: 43.5, 10.1, and 2.2, respectively; all significant) and also associated with ID, ASD, LD, and other developmental delay (aRR ranges: VLBW-Preterm 2.8–5.3; MLBW-Preterm 1.9–2.8; and NBW-Preterm 1.6–2.3). Summary PAFs for preterm birth and/or LBW were 55% for CP, 10%–20% for ASD, ID, LD, and other developmental delay, and less than 5% for ADHD and behavioral-conduct disorders. Findings were similar whether we assessed DDs as independent outcomes or within mutually exclusive categories accounting for DD co-occurrence.

Conclusions

Preterm birth has a sizable impact on child neurodevelopment. However, relative associations and population impacts vary widely by DD type.

Introduction

Developmental disabilities (DDs) are chronic conditions associated with significant impairments in physical, cognitive, behavioral, and/or speech/language functioning. The prevalence of DDs in US children is estimated at 15% overall [1] and ranges from less than 1% (e.g., cerebral palsy [CP]) [2] to 9% (e.g., attention-deficit-hyperactivity disorder [ADHD]) [3]. In addition to functional limitations, children with DDs have increased prevalence of many health conditions including asthma, eczema, gastrointestinal disorders, and obesity [4], [5]. Although the causes of a few DDs are well defined (e.g., intellectual disability [ID] linked to select genetic conditions or fetal alcohol syndrome), for most DDs, etiology is complex and multifactorial [6], [7], [8], [9], [10].

Although numerous studies document associations between preterm birth (PTB) and low birth weight (LBW) and DDs such as CP [8], [11], [12], ID [12], [13], [14], [15], [16], [17], autism spectrum disorder (ASD) [12], [13], [18], ADHD [12], [19], [20], learning disability (LD) [12], [21], and general developmental delay [12], [22], [23], there is limited assessment of population impacts. Studies of population attributable fractions (PAFs) in US populations include an assessment of the Georgia Pregnancy Risk Assessment Monitoring System which estimated 42% of CP cases and 13% of ID cases were attributable to LBW [24], an assessment of North Dakota registry data which estimated 8% of ASD cases were attributable to low gestation and 8% were attributable to LBW [25], and an assessment of the Autism and Developmental Disabilities Monitoring Network which estimated 12% of ASD cases were attributable to PTB, LBW, and Cesarean delivery [26]. Studies from other countries of the impacts of various pregnancy complications and/or outcomes on ASD [27], ADHD [20], and developmental delays [28] reported moderate PAFs for the various perinatal factors studied. These past studies had notable limitations. Most did not assess the known overlap between the perinatal factors studied, all only assessed one or two DDs, and none assessed potential effects from co-occurring DDs. A high proportion of children with DDs meet diagnostic criteria for multiple DDs [29], [30]. Boulet et al. [29] reported that 43%–96% of US children with specific DD diagnoses had more than one DD diagnosis.

Using data from the 2011–2012 National Survey of Children's Health (NSCH), we assessed associations and population impacts of PTB and LBW on subsequent DDs including CP, ID, ASD, ADHD, LD, behavioral or conduct problems or disorder (BCD), and other developmental delay. In addition to assessing a broad array of DDs side by side, we designed analyses to account for DD co-occurrence and examined a finer gradation of PTB and LBW risk than prior studies. To our knowledge, this is the largest and most comprehensive assessment of PAFs for DDs in a US population and the first-to-consider DD co-occurrence.

Section snippets

Study population

The NSCH is a periodic random-digit-dial health survey of US noninstitutionalized children. Households are the primary sampling unit; from contacted households with children, one child is randomly selected. The survey is administered to a parent or guardian knowledgeable about the selected child's health. The overall response rate for the 2011–2012 NSCH was 23% [31]. Nonresponse was more common for cell-phone numbers than landlines. Among contacted households with children, the interview

Results

Overall, 13.9% of children had one or more DD. Individual estimates ranged from 0.24% for CP to 8.2% for ADHD (Table 1). The percentage range for mutually exclusive DD categories was narrower: 0.24% for CP to 5.6% for ADHD. Overall, 49% of children with DDs had greater than 1 DD and 23% had greater than 2 DDs. Thus, only 57% of children with ID, 34% of children with LD, and 13% of children with other developmental delay, were included in the respective mutually exclusive groups for these DDs.

Discussion

In this US nationally representative sample of children, PTB explained more than 50% of CP diagnoses, 15%–20% of ID and other developmental delay diagnoses, and 10%–15% of ASD and LD diagnoses. For CP, both aRRs and component PAFs showed a dose-response pattern: VLBW-PTBs explained substantially more CP than MLBW-PTBs, which explained substantially more CP than NBW-PTBs. For ASD, ID, LD, and other developmental delay, the VLBW-Preterm, MLBW-Preterm, and NBW-Preterm contributions were more

Conclusion

Despite recent declines, PTB remains common; 11.6% of US births in 2012 were preterm and 3.4% were very preterm (<37 and <34-week gestation, respectively) [34]. This study demonstrates the sizable contribution of PTB on child neurodevelopment. Efforts to control PTB are complex. Moreover, while our findings are informative on a population level, they do not indicate which PTB etiologic subgroups most contribute to the associations between PTB and DDs. Nonetheless, these findings highlight the

Acknowledgment

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease and Control and Prevention.

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