Height is more straightforward, but the method of measuring it changes after the first trimester. For the first 13 weeks, fetal height is measured from the top of the head to the bottom.

Moreover, researchers have compared different methods of measuring fetal thymus size to determine the most effective approach for screening gestational diabetes. One study concluded that the fetal ...

Low first trimester vitamin D concentrations are associated with risk for preterm birth; higher levels correlate with fetal growth.