Weight gain in pregnancy varies greatly. Most pregnant women gain between 9kg and 14kg, with most of the weight gain occurring after the 20th week of pregnancy.
Much of the extra weight is due to your baby’s growth, but your body will also be storing fat, ready to make breast milk after your baby is born.
Putting on too much or too little weight can lead to health problems for you or your unborn baby.
How much weight ;should you; put on while pregnant is based on your body mass index (BMI) before pregnancy. BMI is a measure of body fat calculated from your weight and height
Some general guidelines for pregnancy weight gain:
| Pre-pregnancy weight | Recommended weight gain |
|---|---|
| Source: Institute of Medicine and National Research Council | |
| Underweight (BMI less than 18.5) | from 13 to 18 kg approximately |
| Normal weight (BMI 18.5 to 24.9) | from 11 to 16 kg approximately |
| Overweight (BMI 25 to 29.9) | from 7 to 11 kg approximately |
| Obesity (BMI 30 or more) | circa 5-9 kg |
Some general guidelines for weight gain in the event of a twin pregnancy:
| Pre-pregnancy weight | Recommended weight gain |
|---|---|
| Normal weight (BMI 18.5 to 24.9) | from 17 to 25 kg approximately |
| Overweight (BMI 25 to 29.9) | from 14 to 23 kg approximately |
| Obesity (BMI 30 or more) | from 11 to 19 kg approximately |
Getting too fat during pregnancy
Putting on too much weight can affect your health and raise your blood pressure. But pregnancy is not the time to go on a diet, as it could damage the health of the unborn baby.
It is important to eat healthily.
Gaining weight can increase your risk of complications.
These include:
- Gestational diabetes: Too much glucose (sugar) in the blood during pregnancy can cause gestational diabetes, which increases the risk of having a large baby.
- pre-eclampsia: An increase in blood pressure may be the first sign of pre-eclampsia; although most cases are mild and cause no problems, they can be serious.
Gain too little weight during pregnancy
Gaining too little weight can cause problems such as premature birth and a baby with a low birth weight (less than 2.5 kg at birth). It can also mean that your body isn’t storing enough fat.
Lack of weight gain may be related to diet and weight before becoming pregnant. But some naturally slim women stay slim during pregnancy and have healthy babies.
When to worry
If you are concerned about your weight or any other aspect of your health during pregnancy, seek advice from your midwife or GP.
They may have specific advice to give you, depending on your state of health, and in particular if you weigh less than 50Kg or more than 100Kg.
Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.
She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform, Maternicity.com.