Birthweight
High Birthweight
High birthweight (HBW), or macrosomia (large body), in an infant also increases the risk to the infant and mother. A widely agreed upon definition of macrosomia has yet to be established but often-used definitions include a birthweight equal to or exceeding 4,000 grams (8 pounds, 12 ounces), 4,250 grams (9 pounds, 4 ounces), or 4,500 grams (9 pounds, 14 ounces), as well as a birth weighing at or above the ninetieth percentile of birthweights for the infant's gestational age. While one-third of macrosomic births are still unexplained, several factors are known to contribute to excessive fetal size, including large size of parents (especially the mother), multiparity diabetes in the mother, and prolonged gestation. Older maternal age, male infants, and previous delivery of a high birthweight infant also seem to be indicative of macrosomic births. Babies of diabetic women are usually large at birth, but they behave clinically as if they are immature. These infants are not longer in average length but have increased fetal weight. Because glucose, a substance necessary for fetal growth, is elevated in both diabetic and obese women, these mothers are more likely to have macrosomic births.
Risks for birth injuries rise rapidly for heavier babies, with vaginal deliveries being related to higher morbidity and mortality for both the infant and the mother. Lacerations of the birth canal and hemorrhaging may occur to the mother, fetal death may occur due to asphyxia (lack of oxygen), and infants may suffer broken clavicles and neurological damage. While cesarean delivery has been prescribed as the best delivery method to prevent fetal death or injury, others suggest that vaginal birth is still possible for some macrosomic infants.
See also: INFANT MORTALITY; PREMATURE INFANTS
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Martha Slay
Greg R. Alexander
Mary Ann Pass
Additional topics
Social Issues ReferenceChild Development Reference - Vol 2Birthweight - Low Birthweight, High Birthweight