Macrosomia is also known as "big baby syndrome." This is when the fetus or baby is unusually large for gestational age (above 90th percentile) and puts mother and baby at risk for birth complications.
The risk for macrosomia is increased with gestational diabetes and preexisting diabetes in pregnancy. When maternal blood glucose levels are high, babies can gain extra weight due to extra glucose exposure and ingestion. Risk can be lowered for both gestational diabetes and preexisting diabetes in pregnancy by avoiding high glucose levels and maintaining good control.
Diagnosis usually does not occur until after birth. However, it can sometimes be seen on ultrasound, although estimations are not exact.
This condition increases the need for a Cesarean section. Macrosomia can also cause shoulder dystocia, a situation where delivery is complicated because the baby's shoulders get caught behind the mother's pubic bone or caught on the sacrum. Special maneuvers may be required to pass through the birthing canal, which pose a risk of injury to mother and baby.
Sources:
Macrosomia. Medline Plus. National Institutes of Health. Accessed: July 5, 2011. http://www.nlm.nih.gov/medlineplus/ency/article/002251.htm
