Weight gain during pregnancy

Weight gain is a source of great anxiety to many pregnant women. You may worry about putting on too much weight during pregnancy, and not being able to lose it afterwards, or about not gaining enough, and how this might affect your baby. In fact, women vary tremendously in the amount of weight gain during pregnancy, and there’s no such thing as an ideal weight gain.

On average, a healthy, average-sized woman who eats normally in pregnancy will gain around 12.5kg, but women can gain anything from almost nothing to up to 23kg – and still have a normal pregnancy and a healthy baby. A lot depends on your pre-pregnancy weight, your metabolism and your level of activity.

The weight you gain is made up of baby, placenta, amniotic fluid, increased uterine muscle, enlarged breasts, extra blood, extra fluid and extra fat supplies (needed for making breastmilk). Most weight is gained between 4 and 7 months, although for some women the pattern is quite different.

Although the range of normal weight gain is large, there are disadvantages to being at the outer limits of it.

At the lower end, a very low weight gain tends to be associated with lower birthweight babies, especially if associated with smoking, or poor diet, or drug or alcohol abuse. However, if you are a non-smoker, basically well, and eating a healthy diet, simply eating more will not increase the weight of your baby.

At the upper end, gaining a lot of weight makes you more likely to develop varicose veins and to have problems with breathlessness, heartburn or swelling. There is also an increased risk of developing complications such as high blood pressure, pregnancy-related diabetes or pre-eclampsia. This is why most experts would recommend that very overweight women try to lose some weight before becoming pregnant. If this is not possible, expert dietary advice may help prevent further unhealthy weight gain.

Do not be surprised if, after your initial visit, you are not routinely weighed during your antenatal checks. Research has shown that weighing during pregnancy is often inaccurate, a source of considerable anxiety, and unhelpful in clinical terms. Routine weighing is now generally reserved for women who are significantly over- or under-weight (although some pre-eclampsia experts still recommend weighing as part of routine screening for this condition).

What can I do about it?

• Rather than worrying too much about precisely how much, or how little weight you have gained, the important thing is that you eat well. Pregnancy is not a time for dieting, nor for eating too many empty calories. Both you and your baby need to be well nourished. Eat a full and balanced diet, and your body will take care of the rest.
• If you have a pre-existing weight problem – either too heavy or too light – ask your midwife or doctor to refer you to a dietician for guidance. Many women in these situations benefit from specific dietary advice and/or expert counselling.
• Some women weigh themselves regularly at home. If you chose to do this, do not weigh yourself more than fortnightly, and try to standardise when and how you weigh yourself, in order to minimise the normal fluctuations that occur during each day.

If you notice that you are putting on weight very rapidly in the last three months of pregnancy, tell your midwife or doctor. Sudden weight gain may indicate acute fluid retention – a possible sign of pre-eclampsia.

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