Agreement between self-reported birth weight and birth certificate weights.

Area of Science:

• Epidemiology
• Public Health
• Medical Research

Background:

• Birth weight is an emerging risk factor for adult-onset chronic diseases, including breast cancer.
• Participant recall of early life exposures is common in epidemiological studies, necessitating accuracy validation.
• The Western New York Exposures and Breast Cancer (WEB) Study investigates environmental exposures and breast cancer risk.

Purpose of the Study:

• To assess the accuracy of self-reported birth weight compared to birth certificate records.
• To evaluate the reliability of recalled birth weight data for epidemiological research.
• To determine if recall accuracy differs between breast cancer cases and controls.

Main Methods:

• A case-control study comparing self-reported birth weight with birth certificate data in 180 women aged 35-51.
• Birth weights were categorized, and agreement was assessed using Spearman correlation and kappa statistics (κ).
• Analyses were stratified by case-control status and examined demographic/anthropometric correlates.

Main Results:

• Spearman correlation between recalled and actual birth weight was 0.67 (cases: 0.67, controls: 0.68).
• Sixty percent of participants reported exact birth weight; unweighted kappa was 0.39, weighted kappa was 0.68.
• Controls had higher unweighted kappa (0.51) than cases (0.27; P=0.03), but weighted kappa showed no significant difference.

Conclusions:

• Self-reported birth weight demonstrates fair to moderate agreement with birth certificate data.
• Recalled birth weight may be acceptable for some epidemiological analyses, but limitations exist, particularly for case groups.
• Further validation is needed for studies relying on birth weight recall for chronic disease risk assessment.