It's natural and healthy to put on weight during pregnancy. Your body needs to change to help you grow your baby and to give him the best start in life.
Your midwife will weigh you the first time you see her, which will be at your booking appointment. She will then work out your BMI. You will also be weighed during your third trimester, particularly if you have gained a lot of weight. Putting on more weight than you expected may affect your plan for labour.
To check how well your baby is growing, your midwife will measure the size of your bump. If the measurement is smaller or greater than average your midwife may suggest you have an ultrasound scan. A scan will give a better idea of how your baby is growing.
Your body mass index (BMI) measures your weight in relation to your height. It's an accurate way of telling whether or not your weight is in the healthy range. The amount of weight that you should put on in pregnancy depends on what your BMI was before you were pregnant.
There are no official UK guidelines for how much weight you should gain over your pregnancy. There is only general advice that most women put on somewhere between 10kg and 12.5kg (22lb to 28lb). You'll gain most of the weight after 20 weeks.
See below for average weight gain:
Weight in Pregnancy
| Pre-pregnancy BMI | BMI | Total Weight Gain | Rates of weight gain 2nd & 3rd trimester (average range/week) |
| Underweight | less than 18.5 | 13kg-18kg (28lbs-40lbs) | 0.5kg - 0.6kg (1lb-1.3lb) |
| Normal weight | 18.5 to 24.9 | 11.5kg-16kg (25-35lbs) | 0.4kg-0.5kg (0.8lb-1lb) |
| Overweight | 25 to 29.9 | 7kg-11.5kg (15lbs to 25lbs) | 0.2kg-0.3kg (0.5lb-0.7lb) |
| Obese | 30 or more | 5kg-9kg (11lbs-20lbs) | 0.2kg-0.3kg (0.4lb-0.6lb) |