Pregnancy weight gain calculator

Weeks above forty-two are rejected with invalid_input so post-term outliers never invent a schedule.

How to call the API and what comes back

Pre-pregnancy BMI must lie between ten and sixty kilograms per square metre. Fractional weeks are accepted for mid-week checks. Send a JSON body with two required finite numbers: bmi (aliases pre_pregnancy_bmi, prepregnancy_bmi, bmi_pre, pre_bmi) and weeks (aliases gestation_weeks, gestational_weeks, week, ga_weeks). Gestational weeks must be at least zero and at most forty-two; any value strictly greater than forty-two returns invalid_input. On success the response echoes rounded bmi and weeks, sets bmi_category to underweight, normal, overweight, or obese, category_label to a human English band name, guideline to IOM/NRC 2009, pregnancy_type to singleton, gain_min_kg and gain_max_kg to the cumulative recommended range at that week, gain_min_lb and gain_max_lb as pound equivalents, total_recommended_min_kg and total_recommended_max_kg for full-term totals with matching pound fields, weekly_rate_min_kg and weekly_rate_max_kg for the second- and third-trimester rates, first_trimester_min_kg and first_trimester_max_kg for the derived week-thirteen endpoints, unit_primary as kg, message as a short English summary, and steps as an ordered array of classification and interpolation lines. Failed validation—missing fields, non-finite numbers, BMI outside limits, negative weeks, or weeks above forty-two—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item and zero marginal unit price.

Practical tips, limits, and related searches

Use true pre-pregnancy BMI, not a mid-pregnancy BMI, when selecting the band; mixing current weight into the BMI field will misclassify the guideline row. Prefer numbers rather than pre-formatted strings when you control the client; string numbers are accepted only when they match a strict finite numeric pattern. Prefer this capability when you already have pre-pregnancy BMI and gestational age and only need the published range; if your source is height and weight, compute BMI first. When teaching, pair examples: BMI twenty-two at twenty weeks (normal band, mid-pregnancy cumulative range), BMI seventeen at forty weeks (underweight full-term totals near twelve point five to eighteen kilograms), BMI twenty-eight at twelve weeks (overweight first-trimester ramp), and deliberate weeks equals forty-three to demonstrate the hard invalid_input path for gestation beyond forty-two. This landing targets people searching for a pregnancy weight gain calculator, IOM gestational weight gain by BMI, or recommended weight gain by weeks online; it is not a BMI calculator from height and weight, not a twin-pregnancy schedule, not a calorie planner, and not medical advice. Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately set weeks above forty-two. Round-trip checks are easy: confirm the BMI category matches WHO cut-points, confirm full-term totals match the IOM table for that band, and at week forty confirm cumulative gain_min_kg and gain_max_kg equal the published totals within the same twelve-decimal rounding.