Macrosomia is a term that describes an unusually large baby, weighing more than 9 pounds 15 ounces. Aside from genetic factors (others in the family are really big), one of the main causes of macorsomia is poorly controlled diabetes during pregnancy. Increased maternal plasma glucose levels, as well as insulin, stimulate the baby’s growth. Pregnant women who are obese are at increased risk of having an overly large baby. If a baby goes way past its due date, it may be overly large. Interestingly, more male babies are macrosomic than girls, and if you have had one overly large baby you may be at increased risk of having another large baby in a future pregnancy. I know a guy who is one of four boys, each of whom weighed over 14 pounds! I kid you not.
With a really big baby, there is the chance of having a difficult birth. The mother may experience perineal tearing, significant blood loss, and even damage to her tailbone. The baby’s shoulder may get caught behind the mother’s pubic bone causing a dangerous situation and a threat to both the mother and baby, including possible infant death.
Some doctors will plan a cesarean delivery if a woman appears to be carrying a very large baby. Unfortunately, late third trimester ultrasounds are not particularly accurate at measuring the baby’s size and many planned, cautionary cesarean deliveries turn out to be unnecessary. It is always important to go over the risks and benefits to both mom and baby when discussing a planned cesarean delivery.
If you are planning for a baby in you future, now is the time to get your weight under control. If you have diabetes, be sure to manage it carefully so that it is as controlled as possible during your pregnancy. If you have recently had a very large baby and had gestational diabetes, make sure your doctor tests you for diabetes a few months after delivery. Up to 20% of women who had gestational diabetes end up with postpartum diabetes and will need to manage it.