Registration completeness and international comparisons of infant mortality

Area of Science:

• Perinatology
• Public Health
• Biostatistics

Background:

• Infant mortality rates vary significantly, with the United States having higher rates than some European countries.
• Low birth weight is a critical determinant of infant survival, showing a 17-fold increase in mortality compared to normal birth weight infants.
• Existing data suggest birth weight is a more significant predictor of infant mortality than factors like race, sex, maternal age, or birth order.

Purpose of the Study:

• To investigate the relationship between birth weight and infant mortality across different countries.
• To examine the hypothesis that higher infant mortality rates in some countries are due to underregistration of low birth weight infants.
• To determine if physical development indices should be incorporated into infant mortality assessments.

Main Methods:

• Comparative analysis of live birth distributions by birth weight for Denmark, England and Wales, New Zealand, and the United States.
• Examination of infant mortality data for Denmark and the United States.
• Statistical assessment to compare mortality rates across different birth weight categories and countries.

Main Results:

• The data indicate that birth weight is a primary determinant of infant survival.
• Analysis of birth weight distributions and infant mortality rates did not support the hypothesis of widespread underregistration of low birth weight infants in other countries.
• Infant mortality variations linked to birth weight were greater than variations attributed to race, sex, maternal age, or birth order.

Conclusions:

• Physical development, specifically birth weight and gestation, is the most crucial factor influencing infant survival.
• The findings challenge the notion of significant underregistration of low birth weight births in countries with lower reported infant mortality rates.
• It is recommended that indices of physical development, such as birth weight and gestational age, be included in all infant mortality evaluations.