Firstly, it is important to accept that you are going to put on weight during pregnancy. Here's where the extra weight comes from:

• At birth, the average baby will weigh approximately 7.3lb

• During pregnancy your uterus grows dramatically and weighs an extra 2lb.

• The placenta , or afterbirth, which keeps your baby nourished weighs 1.3lb.

• Your breasts weigh an extra 0.9lb.

• Your blood volume increases and weighs an extra 2.6lb

• You have extra fluid in your body, and amniotic fluid around the baby, weighing 5.7lb.

• Plus, you will lay down some fat during your pregnancy to provide you with extra energy for breastfeeding. This comes to about 5.5lb.

So, by the end of pregnancy you will weigh about 24.2lb more than you did before you became pregnant.

This is an average weight gain but of course. The amount of weight you should gain will depend on how heavy you were before you became pregnant. Generally if you are overweight you should gain less than someone who is underweight.

Your BMI and pregnancy weight gain

Women should aim for a weight gain related to their pre-pregnancy BMI (calculate yours here):

• If your BMI was less than 19.8, you should aim for a weight gain of between 28 to 40lb.

• If your BMI was between 19.8 and 26, you should aim for a weight gain of 25 to 35lb.

• If your BMI was above 26, you should aim for a weight gain of 15 to 25lb.

The 1 2 3 rule summarises this in a way that is easy to understand:
• If you were overweight before you became pregnant, you should aim for a weight gain of around 1 stone.

• If you were a normal weight, you should aim for a weight gain of around 2 stone.

• If you were underweight, you should aim for a weight gain of around 3 stone.

If you are under 20 years of age, you should aim for a weight gain at the top end of the range for someone with your pre-pregnancy BMI.

Here's how your BMI is classified:
BMI less than 18.5 - Underweight
BMI 18.5-25 - Ideal
BMI 25-30 - Overweight
BMI 30-40 - Obese
BMI greater than 40 - Severely obese

Controlling your weight

All you really need to do is to eat sensibly, bearing in mind that a pregnant woman needs approximately 2,500 calories a day. A sensible diet includes five portions of fruit and vegetables each day, and foods from all the major food groups:

• About 10 % of your calories should come from proteins, such as meat, fish, and eggs.

• About 35 % of your calories should come from dairy products, such as butter and cheese, and from oils and nuts (fats), slightly less if you are overweight; low fat spreads and yogurts are fine.

• About 55 % of your calories (the largest part) should come from bread, pasta, potatoes, rice and cereals (carbohydrates); wholewheat products are better than refined white, as they will keep your blood sugar steady and you will feel fuller for longer.

There's no harm in having the occasional chocolate treat, but remember that the extra weight you put on during pregnancy will show all too clearly after your baby is born; losing weight in the early months of motherhood isn't going to be easy for everyone.