Caloric Intake During Second Trimester
Women should consume an additional 300 kcal/day during the second trimester to support maternal blood volume expansion, breast and uterine growth, placental development, fetal growth, and amniotic fluid. 1, 2
Standard Recommendation for Normal-Weight Women
The American College of Obstetricians and Gynecologists recommends adding 300 kcal/day during both the second and third trimesters for women with normal pre-pregnancy BMI. 1, 2, 3
No additional calories are needed in the first trimester unless the woman begins pregnancy with depleted body reserves. 1, 2
This 300 kcal/day increase supports the physiological demands of pregnancy including increased maternal blood volume, growth of breast and uterine tissue, placental development, fetal growth, and amniotic fluid production. 1, 2
BMI-Specific Modifications
Obese Women (BMI >30 kg/m²)
Obese women with ample body fat stores may require fewer calories than the standard 300 kcal/day recommendation. 1
Studies have demonstrated successful pregnancy outcomes in obese women consuming only 100 kcal/day above pre-pregnancy intake during the second and third trimesters. 1
A modest energy reduction (33% calorie restriction to 1,600-1,800 kcal/day total) can reduce mean blood glucose without elevating plasma free fatty acids or causing ketonuria in obese women with gestational diabetes. 1
Underweight Women (BMI <19.8 kg/m²)
- Underweight women should gain up to 18 kg total during pregnancy and may require more than the standard 300 kcal/day increase to achieve appropriate weight gain. 1, 2
Critical Safety Threshold
Never prescribe hypocaloric diets below 1,200 calories/day total during pregnancy, as they cause ketonemia and ketonuria, which have been associated with lower intelligence scores in offspring at ages 2-5 years. 1, 4, 2
Even a 50% calorie restriction increases ketonuria approximately twofold compared to more modest restrictions. 1
Daily food records, weekly weight checks, and ketone testing should be used to ensure women are not under-eating. 1, 4, 2
Practical Implementation
Distribute the additional 300 kcal/day across meals and snacks rather than consuming it all at once. 4, 2
Include an evening snack to prevent overnight fasting ketosis and maintain appropriate metabolic function. 1, 4, 2
Energy estimates must be individualized based on food/nutrition assessment, physical activity level, and actual weight gain patterns during pregnancy to ensure appropriate weight gain. 1
Common Pitfalls
Severely restricting calories to avoid excessive weight gain can harm fetal neurodevelopment through maternal ketosis. 1, 4, 2
Failing to adjust caloric intake based on pre-pregnancy BMI may lead to excessive weight gain in obese women or inadequate weight gain in underweight women. 1, 2
The 300 kcal/day recommendation applies to both second AND third trimesters, not just one or the other. 1, 2, 3