Macrosomia is the medical term used to describe a newborn that is abnormally large and weighs more than 8 pounds, 13 ounces at birth. The birth of a macrosomic infant can lead to complications during labor, delivery and postpartum, especially when a baby weighs more than 10 pounds. Obstetricians and nurses are trained to recognize these situations and mitigate the risks.
A baby weighing more than 10 pounds at birth can get his shoulders trapped behind his mother's pelvic bones, according to the website Live Science. This delay in progress through the birth canal can damage nerves in the baby's neck or break collarbones or arms if too much pressure is exerted on the baby's head in an effort to free him. A child that gets stuck in the birth canal can be denied oxygen, and without immediate action, can even die. As noted at the Baby Center website, it is a relatively rare situation, but one that requires intervention by your obstetrician -- often including an unexpected episiotomy.
Increased C-Section Potential
According to the pediatrics department at the New York University Langone Medical Center, obstetricians are more likely to schedule a cesarean section when they have confirmed, prior to labor, that a baby weighs more than 8 pounds and 13 ounces. The caveat is that estimating a baby's pre-birth weight isn't an exact science. As explained in the Journal of Family Practice, ultrasound weight estimations are much more accurate for smaller babies than for larger babies. The JFP reports that only 50 percent of babies weighing more than 9 pounds, 15 ounces actually weigh-in post-birth within 10 percent of the pre-birth ultrasound estimate.
Tailbone Injury to Mother
The increase in the amount of bearing down associated with pushing out a bigger infant during a vaginal birth can injure a woman's tailbone. The pressure caused by the baby passing through the birth canal can bruise, dislocate or even fracture the tailbone, according to Baby Center. General tenderness in the tailbone area -- especially when sitting -- is a common complaint, and tailbone bruising takes about a week to heal. A tailbone fracture is two-fold: It requires a couple of months for the bone to heal, plus additional time for inflammation in the attached muscles and ligaments to dissipate.
Low Blood Sugar at Birth
Sugar is the main nutrient controlling the growth of a baby in the womb, according to Live Science. Larger babies are often born to mothers with gestational diabetes and become accustomed to higher blood sugar levels in the womb. After birth, this access is cut off and can cause an unsafe drop in the infant's blood sugar level. Hypoglycemia -- or low blood sugar -- in a newborn baby can impair the brain's ability to function, according to the Lucile Packard Children's Hospital at Stanford. Indications include blue skin coloring, lethargy and low body temperature. A neonatal pediatrician most likely will order intravenous blood glucose to stabilize the newborn's blood sugar levels and will closely monitor his progress postpartum.