The term is used when your baby’s weight is above the 90th percentile for its gestational age. This often applies to a baby who is estimated to be 9lbs and 15 oz (4500gm) or more at term (37 weeks or more).
A baby can be large if you have gestational diabetes, which can cause your blood sugar to be higher than usual during the majority of your pregnancy, or if you gain a lot of weight during your pregnancy. Genetics also play a significant role in the size of the baby.
The main problem with having a macrosomic baby is that the delivery might be more complicated. There is a higher chance for your baby’s shoulders to get stuck in the birth canal after the head has been delivered. This is called a “shoulder dystocia” and can lead to injury to the baby.
There is also a higher chance that you would need a cesarean birth since the baby will sometimes not be able to “fit” through the birth canal.
Other issues include a greater degree of tearing of the vaginal area and other areas that support your bladder and rectum, more blood loss with the delivery, and higher chance to have bruising of your tail bone.
Your provider might suggest inducing your labor a little early if the baby appears to be macrosomic.