How GDM Affects Your Baby's Growth
Reviewed by CDE Mehandi Sharma · Updated
The main effect of GDM on a baby is on growth, and the process is worth understanding rather than simply worrying about.
Glucose crosses the placenta; your insulin does not. When your blood sugar runs high over weeks, your baby receives extra glucose and produces extra insulin of their own to handle it. That insulin acts as a growth signal.
The result can be macrosomia — a baby larger than expected for their stage of pregnancy. The extra growth is not evenly distributed. It concentrates around the abdomen and shoulders, which is why a larger baby raises the specific concern of shoulder dystocia, where the shoulders become difficult to deliver.
Other effects on the baby can include neonatal hypoglycemia, jaundice, polycythemia, and breathing difficulties after birth. These are the reasons babies are monitored closely in their first hours.
Growth scans are how this is watched. Measurements of the head, abdomen and thigh bone give an estimated weight and a percentile. "Large for gestational age" means above the expected range for the number of weeks.
Two honest points. Scan estimates carry a real margin of error, so a single measurement is not a verdict. And good glucose control genuinely changes this — it is the reason the whole management plan exists.