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Setting the weight record straight

by SRC Health on March 12, 2020

Approximate Reading Time: 4 minutes

Body Baby & Diet #1 - Setting the weight record straight

Weight gain during pregnancy has been widely accepted as essential for optimal pregnancy outcomes. Pregnancy weight is made up of several components, including water (62 %), fat mass (30%) and fat-free protein mass (8%)1. The increase in fat mass is isolated around the inner thigh and to a lesser extent the hips and truck in preparation for breast feeding 2.  Fat gain (approx. 3.3kg) is usually greater in women who have a higher pre-pregnancy weight and alternatively lower when a low pre-pregnancy weight3.

It is important that weight gain is not seen as the sole factor in a healthy pregnancy. The nutritional adequacy of the diet is of critical importance. Certain groups may in fact gain adequate weight or excess weight due to high-energy dense foods and/or nutrient poor nutrition, however diet may be nutritionally incomplete and promote a risk of adverse pregnancy outcomes4.

The rate of weight gain begins at a much slower pace in the first trimester. Fat stores are gained predominantly between the 10th and 30th week of pregnancy and provide an energy reserve when growth demands are greater in the last part of pregnancy. A third of weight gain should occur in the second trimester, and two-thirds in the third trimester5.Women starting at a higher weight tend to gain more overall weight in pregnancy and have heavier babies, as opposed to women with a low pre- pregnancy weight. Research shows women following restrictive diets for weight control, women with substance abuse problems (including alcohol, nicotine and illicit drugs), and those with underprivileged backgrounds are associated with an increased risk of pre-term delivery or restricted baby growth2.

Many women may require extra support and advice about weight gain and energy intake in pregnancy. These include women who were underweight or overweight before pregnancy, those with a current or previous history of an eating disorder, and those who are ceasing or reducing smoking. Women who have been restrained eaters prior to pregnancy may see pregnancy as an opening to eat without constraint6. It would be highly recommended to consult with a general practitioner and/or nutritionist for advice in any of these circumstances.

Table 1: Recommended total weight gain in pregnant women, by pre-pregnancy BMI (kg/m2)

Weight-for-height category

Recommended total gain (kg)

Low (BMI < 19.8) 

Normal (BMI 19.8–26.0) 

High BMI (BMI >26.0–29.0) 

 Obese (BMI > 29.0)





7.Source: Institute of Medicine 1990.

Notes: Adolescents should strive for gains at the upper end of the recommended range.

Short women (< 1.57 m) should strive for gains at the lower end of the range.

The BMI index can be used as a guide for women and can be used to determine any weight extremes. It is a tool that uses height and weight to determine weight ranges (see table 2).It should be noted that there are limitations to the BMI, namely, not taking muscle mass, fat mass or frame into consideration. For women in the normal range of pre-pregnancy BMI, the recommended rate of gain is approximately 0.4 kg/week in the second and third trimesters; for women in the underweight range of pre-pregnancy BMI it is approximately 0.5 kg/week; and for women in the overweight range of pre-pregnancy BMI it is approximately 0.3 kg/week. For obese women the rate should be determined on an individual basis7.

Table 3: Appropriate BMI cut-offs 


BMI Kg/m2


Normal weight




18.5 – 25

25 - 30

> 30

Ultimately, the main goals are to provide adequate nutrition to baby and mother. Weight gain is important but nutritional adequacy is critical. Aim to keep to healthy weight ranges with the support if required. Keep reading and make note of some easy nutrition tips to begin the road to a healthy weight gain.


Nutrition Tips for your baby body!

    1. Sustainable energy - slow releasing carbohydrates or low GI carbohydrates for consistent energy and weight control. (choose grainy breads and cereals, whole fruits and vegetables)
    2. Increase lean protein – choose proteins to increase satiety and for muscle growth and repair namely fish, pork ,tuna, eggs, low fat dairy, nuts, legumes and lentil)
    3. Carbohydrate control- carbohydrates are essential for sustainable energy however too much of anything is never a good thing. Control portions.
    4. Variety is key to meet vitamin and mineral requirements, 3-4 serves of calcium, 2-3 serves of fruit, 5 or more vegetables 
    5. Consuming for two is a myth but increasing intake of certain vitamins, minerals and protein is essential and true.


  1. Hytten FE, Leitch I. 1971. The Physiology of Human Pregnancy. Oxford: Blackwell Scientific Publications Ltd. 
  2. Butte NF, Hopkinson JM. 1998. Body composition changes during lactation are highly variable among women. Journal of Nutrition 128(2): S381–5. 
  3. Butte NF, Ellis KJ, Wong WW, et al. 2003. Composition of gestational weight gain impacts, maternal fat retention and infant birth weight. American Journal of Obstetrics and Gynecology 189(5): 1423–32.
  4. Kramer MS. 1998a. Maternal nutrition, pregnancy outcome and public health policy. Canadian Medical Association Journal 159(6): 663–5.
  5. NHMRC. 2006. Nutrient Reference Values for Australia and New Zealand including Recommended Dietary Intakes. Canberra: NHMRC, Wellington: Ministry of Health.
  6. Clark M, Ogden J. 1999. The impact of pregnancy on eating behaviour and aspects of weight International Journal of Obesity and Related Metabolic Disorders 23(1): 18–24.
  7. Institute of Medicine. 1990. Nutrition During Pregnancy. Part I: Weight gain. Part II: Nutrient supplements. Washington: National Academy Press.

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