Overweight Newborn Categories
Newborns are classified as large for gestational age (LGA) when their birth weight exceeds the 90th percentile for their gestational age, which represents the standard definition for overweight newborns used in clinical practice. 1
Standard Classification System
The birth weight percentile classification system categorizes newborns into three main groups based on their weight relative to gestational age:
- Small for gestational age (SGA): Birth weight below the 10th percentile for gestational age 2
- Appropriate for gestational age (AGA): Birth weight between the 10th and 90th percentiles for gestational age 1, 3
- Large for gestational age (LGA): Birth weight above the 90th percentile for gestational age 1, 4
Severe Categories
More severe classifications exist at the extremes of the distribution:
- Severe growth restriction: Birth weight below the 3rd percentile, associated with 3-fold increased risk of stillbirth compared to the 3rd-5th percentile group 2
- Macrosomia: Absolute birth weight exceeding 4,500 grams, regardless of gestational age percentile 1
Clinical Significance of LGA Classification
Large for gestational age newborns face substantially increased risks of both immediate and long-term complications. 4
Short-term complications in LGA infants include:
- Neonatal intensive care unit admission 4
- Respiratory distress 4
- Neonatal hypoglycemia and other metabolic abnormalities 4
- Birth trauma 4
- Increased risk of stillbirth or neonatal death 4
Long-term health risks for individuals born LGA include:
- Increased risk of childhood and adult overweight/obesity 4, 5
- Elevated risk of diabetes 4
- Increased cardiovascular disease risk 4, 6
- Possible increased risk of certain childhood cancers 4
Important Clinical Considerations
The traditional birth weight percentile classification does not accurately reflect body fat percentage in newborns. Among term infants classified as appropriate for gestational age, 42.9% actually had less than 10% body fat, and 9.9% of all AGA newborns had less than 10% body fat. 3
Population-based birth weight charts are recommended over customized charts for clinical decision-making. Both approaches identify similar risks for long-term adverse outcomes, but population charts provide standardized reference points. 7, 6 The Society for Maternal-Fetal Medicine and American College of Obstetricians and Gynecologists recommend using population-based references rather than customized standards when determining fetal weight percentiles. 7
Maternal Weight Gain and LGA Risk
Excessive maternal weight gain substantially increases the risk of delivering an LGA infant:
- Weight gain above Institute of Medicine recommendations increases odds of LGA by 80% (adjusted OR 1.80,95% CI 1.36-2.38) 1
- Weight gain above recommendations increases macrosomia risk more than 3-fold (adjusted OR 3.36,95% CI 1.74-6.51) 1
- Normal-weight women should not exceed 16 kg total weight gain or 0.9 kg per week after the first trimester 8