How much weight should I gain during pregnancy?

It depends on your pre-pregnancy BMI. Women with a normal BMI (18.5-24.9) are advised to gain 11.5-16 kg total. Underweight women should gain more (12.5-18 kg) and overweight women less (7-11.5 kg). These ranges are associated with the best outcomes for mother and baby.

When does most pregnancy weight gain occur?

Most weight gain happens in the second and third trimesters. In the first trimester, total gain is typically just 0.5-2 kg. From week 13 onwards, normal-weight women gain approximately 0.4-0.5 kg per week. Weight gain may slow slightly in the final weeks.

Is it safe to lose weight during pregnancy?

Intentional weight loss during pregnancy is generally not recommended. Even for women with obesity, the focus should be on gaining within the lower recommended range rather than losing weight. Always discuss weight management with your obstetrician or midwife.

What are these guidelines based on?

These recommendations follow the IOM 2009 guidelines, which are used in Australian clinical practice. They are based on extensive research linking maternal weight gain to outcomes for both mother and baby, including birth weight, caesarean delivery rates, and postpartum weight retention.

Pregnancy Weight Gain Calculator

This calculator provides recommended weight gain targets during pregnancy based on your pre-pregnancy BMI. The guidelines follow the Institute of Medicine (IOM) 2009 recommendations, which are endorsed by Australian clinical practice guidelines for pregnancy care published by the Australian Government Department of Health.

Enter Your Details

Pre-pregnancy Weight

Height

Current Week of Pregnancy

weeks

How It Works

Your pre-pregnancy BMI determines your recommended total weight gain range: Underweight (BMI < 18.5): 12.5-18 kg, Normal weight (BMI 18.5-24.9): 11.5-16 kg, Overweight (BMI 25-29.9): 7-11.5 kg, Obese (BMI 30+): 5-9 kg. Weight gain is minimal in the first trimester (0.5-2 kg total) and then approximately 0.4-0.5 kg per week in the second and third trimesters for normal-weight women.

Quick Reference

Pre-pregnancy BMI	Category	Total Gain (kg)	Weekly Gain T2/T3 (kg)
< 18.5	Underweight	12.5 – 18.0	0.44 – 0.58
18.5 – 24.9	Normal weight	11.5 – 16.0	0.36 – 0.45
25.0 – 29.9	Overweight	7.0 – 11.5	0.23 – 0.33
30.0+	Obese	5.0 – 9.0	0.17 – 0.27

Based on IOM 2009 guidelines, endorsed by Australian clinical practice guidelines for pregnancy care. T2/T3 = second and third trimesters.

Frequently Asked Questions

How much weight should I gain during pregnancy?: It depends on your pre-pregnancy BMI. Women with a normal BMI (18.5-24.9) are advised to gain 11.5-16 kg total. Underweight women should gain more (12.5-18 kg) and overweight women less (7-11.5 kg). These ranges are associated with the best outcomes for mother and baby.
When does most pregnancy weight gain occur?: Most weight gain happens in the second and third trimesters. In the first trimester, total gain is typically just 0.5-2 kg. From week 13 onwards, normal-weight women gain approximately 0.4-0.5 kg per week. Weight gain may slow slightly in the final weeks.
Is it safe to lose weight during pregnancy?: Intentional weight loss during pregnancy is generally not recommended. Even for women with obesity, the focus should be on gaining within the lower recommended range rather than losing weight. Always discuss weight management with your obstetrician or midwife.
What are these guidelines based on?: These recommendations follow the IOM 2009 guidelines, which are used in Australian clinical practice. They are based on extensive research linking maternal weight gain to outcomes for both mother and baby, including birth weight, caesarean delivery rates, and postpartum weight retention.

Pregnancy Weight Gain Guidelines

Pre-pregnancy BMI = weight (kg) / height (m)^2 First trimester: 0.5 – 2.0 kg total Second & third trimesters: weekly rate based on BMI category

BMI < 18.5: = underweight - recommended total gain 12.5-18 kg
BMI 18.5-24.9: = normal weight - recommended total gain 11.5-16 kg
BMI 25-29.9: = overweight - recommended total gain 7-11.5 kg
BMI 30+: = obese - recommended total gain 5-9 kg

These guidelines apply to singleton pregnancies. Twin pregnancies have higher recommended gains. Always discuss your weight gain with your obstetrician or midwife.

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Disclaimer

This calculator provides estimates for informational purposes only and should not be considered medical advice. Individual results may vary based on factors not captured by these formulas. Consult a healthcare professional before making changes to your diet or exercise routine, especially if you have any existing health conditions.