Pregnancy Weight Gain for Overweight Women — IOM Guidelines

Why a Lower Weight-Gain Range Is Recommended

Pregnancies that begin with a BMI between 25.0 and 29.9 carry higher baseline risks that excess weight gain can amplify. Studies show that overweight pregnant individuals who gain above the IOM range have a roughly 60% higher risk of developing gestational diabetes and a significantly elevated risk of delivering a large-for-gestational-age baby (macrosomia, birth weight above 4000 grams). Excess gain is also associated with a higher caesarean section rate, increased likelihood of preeclampsia, and greater retained weight postpartum. The IOM set a narrower weight-gain range for this group to minimize these risks while still supporting adequate fetal growth.

IOM Recommendation for Overweight Pregnancies

For a pre-pregnancy BMI of 25.0 to 29.9, the IOM recommends a total singleton pregnancy weight gain of 6.8 to 11.3 kg (15 to 25 lb). In the first trimester, gain of 0.5 to 2.0 kg is typical. In the second and third trimesters, the recommended weekly rate is 0.28 kg (0.5 to 0.7 lb) per week, which totals roughly 7.5 to 10.5 kg across the remaining 27 weeks. Importantly, this range does not restrict the mother to inadequate nutrition. It focuses the additional pregnancy calories on nutrient-dense foods while moderating total energy intake. Staying within this range is associated with lower gestational diabetes rates and improved neonatal outcomes in this population.

Nutrient Focus Over Calorie Counting

The quality of food matters more than the exact calorie number during an overweight pregnancy. Prioritise lean protein at 1.1 to 1.3 grams per kilogram of pre-pregnancy body weight daily, which supports fetal tissue growth and maternal blood volume expansion. Include at least 2 servings of low-mercury fish per week for omega-3 DHA. Fill half of each plate with non-starchy vegetables for fiber, vitamins, and minerals. Choose whole-grain carbohydrates over refined ones to maintain steady blood sugar and reduce gestational diabetes risk. Take a prenatal vitamin to ensure adequate folic acid (400 mcg), iron (27 mg), calcium (1000 mg), and vitamin D (600 IU). Limit added sugars to less than 25 grams per day.

Safe Physical Activity During Pregnancy

Regular moderate physical activity helps maintain weight gain within range and reduces gestational diabetes risk by up to 30%. The American College of Obstetricians and Gynecologists (ACOG) recommends at least 150 minutes of moderate-intensity aerobic activity per week, spread across most days. Safe options include brisk walking, stationary cycling, swimming, and prenatal yoga. Activities with a fall risk or abdominal trauma risk, such as contact sports, should be avoided. Strength training at moderate intensity, 2 to 3 times per week, supports healthy muscle maintenance and glucose metabolism. Always consult your prenatal care team before starting or changing an exercise routine.

Monitoring Your Weight-Gain Trajectory

Weekly self-weighing on the same scale at the same time of day provides the best picture of your trajectory. Plot each reading against the IOM range of 6.8 to 11.3 kg total. If your cumulative gain exceeds the range midpoint (about 9 kg) by week 28, you may need to adjust your intake or activity level. Conversely, if your gain is below 3 kg by week 28, discuss dietary adequacy with your care team. Sudden gain of more than 0.5 kg per week for 2 to 3 consecutive weeks should be reported, as it may indicate fluid retention. Bring your weight log to every prenatal visit so your care team can compare it with fundal height measurements and ultrasound growth scans.