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Pregnancy Weight Gain Tracker (IOM Guidelines)

Monitor pregnancy weight gain against official Institute of Medicine (IOM) 2009 recommendations. Calculates safe ranges based on pre-pregnancy BMI and trimester.

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Category Women's Health
Result: Enter data
Pre-Preg BMI--
Category--
Total Gain--
Projected End-of-Pregnancy Range
+25
+35

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About

Appropriate weight gain during pregnancy is a critical factor for maternal and fetal health, reducing risks of gestational diabetes, preeclampsia, and preterm birth. This tracker utilizes the 2009 Institute of Medicine (IOM) guidelines, which adjust recommended gain ranges based on Pre-Pregnancy Body Mass Index (BMI).

Unlike generic calculators, this tool accounts for the non-linear nature of weight gain. The first trimester typically sees minimal gain (1.1 to 4.4 lbs), while the second and third trimesters require steady weekly increases. The tool visualizes your current position relative to the "Safe Corridor" tailored to your specific body composition.

pregnancy BMI weight gain trimester health

Formulas

The BMI is calculated using the standard formula:

BMI = weight(lb) × 703height(in)2

The expected weight W at week t (for t > 13) is modeled as:

Wt = Wstart + Gain1st + [Rate × (t − 13)]

Reference Data

Pre-Pregnancy CategoryBMI Range (kg/m2)Total Gain (lbs)2nd/3rd Tri Rate (lbs/week)
Underweight< 18.528 - 401 (1.0 - 1.3)
Normal Weight18.5 - 24.925 - 351 (0.8 - 1.0)
Overweight25.0 - 29.915 - 250.6 (0.5 - 0.7)
Obese≥ 30.011 - 200.5 (0.4 - 0.6)

Frequently Asked Questions

No. The guidelines used here are strictly for singleton pregnancies. Twin pregnancies require significantly higher weight gain (typically 37-54 lbs for normal BMI) and should be monitored directly by an obstetrician.
Weight loss or stagnation in the first trimester is common due to nausea (morning sickness). If you are within the "Normal" or "Overweight" BMI categories, this is generally not a concern provided you catch up in the second trimester.
BMI is a general screening tool and does not distinguish muscle from fat. However, IOM guidelines generally apply to BMI categories regardless of body composition. Consult your doctor if you have high muscle mass.