Biology Question

Question

Why would a doctor encourage a woman with a body mass index (BMI) of 18 to gain significant weight during pregnancy, while admonishing someone with a BMI of 30 to limit weight gain? What are the impacts on the fetus of undernutrition versus overnutrition? How will this impact the offspring long term?

Answer 1

Many different regulatory systems combine to form a delicate balance, which can be disrupted by changes in weight.

Gestational weight gain above target ranges has these increased risks:

Mother:

- Cesarean delivery

- Pregnancy-related hypertension, including preeclampsia

- Gestational diabetes

- Retention of gained weight following pregnancy

Baby:

- Fetal macrosomia and large for gestational age (LGA) infants

- Childhood overweight status and obesity

- Birth injury

- Respiratory distress and perinatal asyphxia

- Preterm birth

- Changes in blood sugar and blood count

Gestational weight gain below target ranges increases these risks:

Mother:

- Preterm birth

Baby:

- Small for gestational age (SGA) and intrauterine growth restriction (IUGR)

- Complications related to prematurity

- Perinatal asphyxia

- Loss of thermoregulation

- Changes in blood sugar and blood count

- Impaired immune function

These both increase the risk of fetal death and disability.