How are big babies made?

Answer 1

There can be fetuses that are larger than usual for their stage of development (gestational age) and it is nothing to be concerned about, they are called Large for Gestational Age or LGA.

Infants of diabetic mothers are at risk for being very large babies (as high as 12 pounds and up) and it is something that is monitored closely for the health of the mother and fetus, and to make plans if necessary for a C-Section birth. This can be needed if the size of the fetus is too large for the mother to deliver vaginally. It is believed the large size of diabetics' babies it is due to the metabolism of the infant being impacted by the higher blood sugars in the mother. Some women who were not previously diabetic can develop Diabetes during pregnancy, this can be either only for the duration of the pregnancy, or in some cases the condition is permanent. In these women, there is also the concern for the baby's metabolism and size.

Besides that, and assuming good nutrition and prenatal care is being provided, whether a baby is big or small is mostly a factor of genetics or inherited characteristics.