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Estimate your healthy pregnancy weight gain by week with our interactive calculator. Based on IOM and CDC guidelines, it supports both US and metric units and is designed for surrogates and intended parents who want to track a healthy, steady journey from the first trimester to delivery.
This calculator follows the Institute of Medicine (IOM) and CDC guidelines to estimate healthy pregnancy weight gain by week.
It first determines your pre-pregnancy BMI, then applies the IOM’s recommended total weight gain range for your category:
Underweight (BMI < 18.5): 28–40 lb
Normal (18.5–24.9): 25–35 lb
Overweight (25–29.9): 15–25 lb
Obese (≥ 30): 11–20 lb
Twin pregnancy: higher ranges apply
The model assumes gradual gain during the first trimester, then a steady weekly increase through the second and third trimesters, producing a realistic “slow-then-steady” curve.
Each week’s recommended range is calculated so that the total gain at 40 weeks matches the IOM target.
The pink shaded area between the blue and red lines represents the recommended weight range, while the orange dot indicates your current weight.
You’re tracking well. Continue balanced nutrition, hydration, and moderate activity. Small weekly variations are expected — focus on the overall upward trend.
This may occur in early pregnancy due to nausea or low appetite. Your provider can help ensure your baby’s growth stays on track and advise on gradual, healthy weight gain.
Slight excess is common, but persistent over-gain may increase risks such as gestational diabetes or hypertension.
Review your nutrition and lifestyle with your provider; minor adjustments often bring weight back to a healthy path.
Note: This calculator is a screening tool — not a medical diagnosis. Always discuss your results with your healthcare provider.
The Institute of Medicine (IOM) provides the most widely accepted framework for gestational weight gain.
These recommendations balance the mother’s nutritional needs with optimal fetal growth and long-term health outcomes.
| Pre-Pregnancy BMI | Category | Total Recommended Gain | 1st Trimester | 2nd & 3rd Trimester (per week) |
|---|---|---|---|---|
| < 18.5 | Underweight | 28–40 lb (12.5–18 kg) | 2–5 lb (1–2 kg) | 1.0 lb/week (0.45 kg/week) |
| 18.5–24.9 | Normal | 25–35 lb (11.5–16 kg) | 1–4.5 lb (0.5–2 kg) | 1.0 lb/week (0.45 kg/week) |
| 25–29.9 | Overweight | 15–25 lb (7–11.5 kg) | 0.5–2 lb (0.2–1 kg) | 0.6 lb/week (0.27 kg/week) |
| ≥ 30 | Obese | 11–20 lb (5–9 kg) | 0.5–1.5 lb (0.2–0.7 kg) | 0.5 lb/week (0.22 kg/week) |
| Pre-Pregnancy BMI | Category | Total Recommended Gain |
|---|---|---|
| < 18.5 | Underweight | 50–62 lb (22.5–28 kg) |
| 18.5–24.9 | Normal | 37–54 lb (17–25 kg) |
| 25–29.9 | Overweight | 31–50 lb (14–23 kg) |
| ≥ 30 | Obese | 25–42 lb (11–19 kg) |
These guidelines were developed by analyzing pregnancy outcomes in over 120,000 births, correlating maternal gain with rates of preterm birth, fetal growth restriction, and postpartum recovery.
Maintaining a healthy, steady weight gain during pregnancy supports both your own comfort and the baby’s development.
This calculator helps you understand what’s typically considered a healthy range—so you can stay informed and confident throughout your journey.
Every pregnancy is unique. Small variations are normal and can depend on hydration, appetite, and daily activity.
If your result falls slightly outside the recommended range, it’s simply a reminder to keep open communication with your doctor and your Ivy Surrogacy coordinator.
Our team is here to provide encouragement, resources, and guidance whenever you need them.
Together, we’ll help make this journey as smooth and supported as possible.
Ready to begin your own surrogacy journey?
Understanding your surrogate’s pregnancy progress helps you stay emotionally connected to the journey and your growing baby.
This calculator gives you a simple, science-based way to visualize how a healthy pregnancy typically progresses week by week.
Slight differences in weight gain are common and not always a cause for concern.
Your surrogate’s healthcare provider will monitor her health and confirm that both she and the baby are doing well.
At Ivy Surrogacy, we believe in transparency and communication—keeping intended parents informed and reassured every step of the way.
Planning to start your family through surrogacy?
Pregnancy weight gain is one of the most common topics discussed among surrogates and intended parents.
Below are some of the most frequently asked questions about how the Pregnancy Weight Gain Calculator works, what your results mean, and how they relate to healthy pregnancy progress.
It uses validated IOM and CDC equations and provides an accurate educational reference, but it is not a substitute for medical care. Always confirm trends with your healthcare provider.
Some tools assume a fixed first-trimester gain (e.g., +2 lb), while others model it linearly. This calculator uses a realistic, evidence-based curve for smoother transitions.
That’s precisely why we adjust by BMI. Underweight individuals need more total gain for fetal development, while overweight individuals typically need less.
Twin pregnancies require substantially higher caloric intake and nutrient support. The calculator automatically uses IOM twin guidelines (see table above).
Yes. All fields and results are synced; switching units automatically converts and recalculates your numbers.
Yes, mild loss from morning sickness or appetite changes in the first trimester is common. The key is regaining and following an upward trend later.
Being slightly above or below the band is common. Extreme deviations or sudden changes should be discussed with your provider for personalized evaluation.
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⚠️ Disclaimer: This calculator is for educational and informational purposes only. It is not intended to diagnose or treat any medical condition. For personalized medical advice, always consult your physician, OB-GYN, or midwife.
