Why is the first trimester range so much smaller?

Most people gain very little weight in the first trimester, ACOG guidance puts it at just 0.5-2 kg regardless of starting BMI, since fetal growth is minimal early on. Most of the total recommended gain happens in trimesters 2 and 3.

How is this different from the regular Pregnancy Weight Gain calculator?

The Pregnancy Weight Gain calculator gives your overall total-gain range and your expected gain-to-date at a specific week. This calculator instead breaks that same IOM total down into per-trimester targets, useful for pacing your gain across the whole pregnancy.

Pregnancy Weight Gain by Trimester Calculator

See recommended pregnancy weight gain broken down by trimester.

How this is calculated

IOM total-gain range by pre-pregnancy BMI category, with a fixed first-trimester range and the remainder split evenly across trimesters 2 and 3

Assumptions used in this calculation

Simplified distribution: First-trimester gain is treated as a fixed 0.5–2 kg range per ACOG guidance regardless of BMI category; consult your doctor for personalized guidance.

About this calculator

The pregnancy weight gain by trimester calculator breaks down the IOM total pregnancy weight gain guideline into recommended ranges for each of the three trimesters, based on pre-pregnancy BMI.

Worked example

165cm, 60kg pre-pregnancy

Result: 11.5–16 kg total, split by trimester

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Pregnancy Weight Gain by Trimester Calculator

About this calculator

Frequently asked questions

Why is the first trimester range so much smaller?

How is this different from the regular Pregnancy Weight Gain calculator?

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