Weight gain during pregnancy

Being pregnant inevitably means you will gain weight. However, how much weight you gain varies from woman to woman. Whilst it often becomes a source of concern for many pregnant women many caregivers have become less inclined to regularly weigh expectant mums as part of their routine care. Frequent weighing can often only create anxiety for women about ‘not putting on enough’ or ‘putting on too much’ weight.

It is fairly common for caregivers to ask you to weigh yourself as part of your first pregnancy visit. This is aimed at having a ‘baseline’ weight in case the doctor needs to prescribe drug dosages calculated on your average weight at some stage. However, beyond this weighing during pregnancy becomes a little irrelevant. Even so, some caregivers still continue to weigh women as part of their routine antenatal visits.


About weight gain

Whatever your weight was before your pregnancy, and regardless of how much weight you are (or are not) putting on, it is important to have a well-balanced diet with plenty of carbohydrates, protein and fresh fruits and vegetables, with not too many fatty and sugary foods. Pregnancy is not an appropriate time to diet, nor is it an excuse to ‘eat for two’! If you have a special diet, or any health conditions that require diet modification (such as diabetes), you should consult with a dietician about planning your weekly meals.

Many information sources and pregnancy books will try to provide guides about the ‘recommended weight gain’ during pregnancy. These are usually along the lines of ‘putting on 2- 3 kg in the first 20 weeks, then ½ a kilo per week until the baby is due, averaging 12-14 kg in total. While this may be true for some in women, in practise this is rarely the case.

Many women will put on most of their pregnancy weight gain during the first 20 weeks, or only gain a few kilograms up until 12 to 16 weeks of the pregnancy, then experience a large ‘growth spurt’ during the middle of their pregnancy up until about 32 weeks, slowing down their weight gain over the next 4 to 6 weeks and then losing 1 to 2 kg just prior to going into labour. A woman’s overall weight gain when carrying a single baby may be as little as 8 kg, or as much as 20 kg.

NOTE:For conversion, 1 kg = approx. 2.2 lbs. To convert pounds into kilograms you divide the number of pounds by 2.2 (for example, 22 lbs ÷ 2.2 = 10 kg).

The ‘average’ weight gain of around 12 to14 kg can be physically attributed to:


baby = 3 to 4 kg

placenta = 0.5 kg

amniotic fluid = 1 kg

uterus = 1 kg

blood volume = 1.5 kg

breasts = 0.5 kg

Fat stores for breastfeeding = 3.5 kg

Fluid retention = 1.5 kg


Individual differences:

Each woman’s body responds differently to their pregnancy and there are many reasons why individual women will put on more or less weight, at various stages of their pregnancy and yet still be classified as being ‘normal’ for pregnancy. This is particularly the case for women who were not within their ‘ideal weight range’ before they conceived.

While it can be difficult to generalise for each woman, the following are a few suggestions that may explain why you are gaining weight the way you are:

  • Women who were relatively ‘underweight’ for their height before they conceived often find that their body naturally ‘adjusts’ by putting on more weight during pregnancy. This is because necessary fat stores are being laid down by the body to maintain the pregnancy and support breastfeeding after the birth. If this is the case, the woman’s weight will increase by a certain amount (to be more in line with her ‘ideal weight range’ for her height), as well as her expected pregnancy weight gain. Even though the woman does not really look overweight, she has put on quite a few more kilograms than expected.
  • Women who were relatively ‘overweight’ for their height before they conceived often find that they put on very little weight during pregnancy (or perhaps even naturally lose some weight at different stages). This is because the existing fat stores become depleted by the increased physical needs of the pregnancy and an increased metabolism. This is normal and regarded as being safe if you continue to eat a well-balanced diet.
  • If you are excessively sick during the earlier months of pregnancy, you may find you do not put on any weight for a while (or possibly even lose weight). Usually when the nausea and/or vomiting settles, your appetite returns and you have a ‘growth spurt’ for a few weeks, as your body ‘catches up’. Of course if your vomiting gets to the point where you are becoming dehydrated, it may be necessary to see your caregiver and be admitted to the hospital for a drip in the vein, and/or medications to help stop the vomiting.
  • Some women retain more fluid than others. Fluid retention and swelling (or oedema) affects about 65% of healthy pregnant women with a normal blood pressure, usually after about 20 weeks of the pregnancy.
  • Most women carrying twins, triplets or more will put on more weight, however it is not ‘double’ or ‘triple’ the expected amount. Many women carrying multiples find that their weight gain is not that much different from women having a single baby. As a guide for twins you may put on up to 15 to 20 kgs (or more) and for triplets it may be up to 20 to 25 kgs (or more). Be aware that with triplets or quads, your babies will probably be born premature (less than 37 weeks) and therefore your weight gain will generally be put on early and more quickly.


Our thoughts…

Unfortunately, many pregnant women spend a lot of time and energy worrying about their weight gain. This is no doubt a reflection of our society’s obsession with weight and how we look. An obstetrician we know once said, “The worst thing you can give a pregnant woman is a set of scales!” and we tend to agree with him.


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