If a newborn has macrosomia (>4000 g), which postpartum test should be performed to assess maternal risk for diabetes?

• A. Serum fasting glucose
• B. HbA1c
• C. Random glucose
• D. Oral glucose tolerance test

Answer: (A)

Macrosomia in a newborn often signals maternal hyperglycemia during pregnancy, so checking the mother after delivery focuses on detecting ongoing diabetes or prediabetes with a practical screen.

A fasting serum glucose is the simplest and quickest postpartum screen. It can reliably identify overt diabetes when elevated (typically if fasting glucose is consistently high), and it’s easy to perform without special preparation beyond fasting. HbA1c, while useful for longer-term glucose assessment, is less dependable in the peripartum period due to factors like recent pregnancy changes and red blood cell turnover, which can affect accuracy. A random glucose is too variable to rely on for screening. An oral glucose tolerance test is more sensitive and provides a definitive diagnosis, but it’s more cumbersome and less convenient as an initial postpartum screen; it’s typically used to confirm or further evaluate abnormal screening results.

So the fasting glucose serves as the best initial postpartum test to assess maternal risk for diabetes in this context. If abnormal, follow-up with more definitive testing as indicated.