What is considered one of the most reliable predictors of infant health?

Birth weight is considered one of the most reliable predictors of infant health due to its strong association with various health outcomes. Low birth weight, defined as a newborn weighing less than 5 pounds, 8 ounces (2500 grams), is linked to higher rates of infant mortality, developmental delays, and long-term health complications. This correlation stems from the fact that lower birth weight often indicates issues with gestational age, maternal health, and nutritional status during pregnancy, all of which can significantly impact an infant's survival and overall health.

In contrast, factors like length at birth and milk intake during the first week of life, while important, do not provide as robust a predictive value for long-term health outcomes as birth weight. Length at birth is influenced by genetics and may not reflect overall health status as directly as weight. Similarly, while adequate milk intake is vital for nutrition and growth, it is not as strong a predictor of health outcomes as the foundational aspect of birth weight. The presence of visible birth defects can indicate potential health challenges, but not all health issues are visible at birth, making it a less comprehensive indicator than birth weight.