13 January 2021

Section 20: Pregnancy

Significant weight loss can actually boost libido and fertility.


In line with guidance published in October 2014 by the British Obesity & Metabolic Surgery Society (BOMSS), we advise that pregnancy should be avoided for the first 12 to 18 months following surgery. This is to ensure you have reached a stable weight, and helps promote a healthier pregnancy.


If you do fall pregnant, please inform your midwife, GP and Transform Hospital Group, as an appointment with your dietitian may be required to assess your nutrition and provide advice.


Dietary advice


It is vital that you’re healthy and well-nourished before and during pregnancy as this will help to ensure that the baby develops as it should.


It’s essential that you follow this guidance during pregnancy:


  • Eat a well-balanced and varied diet.
  • Eat regular meals.
  • Limit your consumption of fat-rich and sugar-rich foods.
  • Take the appropriate supplements (see later).
  • Observe strict hygiene procedures to lessen the risk of food borne illnesses:
  • Ready-prepared meals should be cooked thoroughly to ensure that all bacteria are killed. This is especially important in meals containing poultry.
  • If fruit and vegetables are being eaten raw, they should be washed thoroughly.
  • Any leftover cooked food should be discarded after 24 hours.


You should also limit:


  • Consumption of oily fish (including tuna) to 2 portions per week to reduce the risk from food contaminants such as dioxins and heavy metals.
  • Alcohol intake to 1-2 units per week, or avoid altogether. One unit equals:
  • ½ pint bitter (3-4% ABV (Alcohol By Volume)
  • Small glass (125mls) of wine (9-10% ABV)
  • One pub measure of spirits (25ml) (e.g. plain vodka, gin, rum, whisky, brandy).
  • Caffeine intake to less than 300mg per day. The caffeine content of food and drink is listed below. Additionally, you should always read the labels of headache, cold and flu medications to avoid caffeine-containing analgesics.



Caffeine content (mg) per 200ml (one mug/glass)





Instant coffee


Filter/percolated coffee


Chocolate drinks




‘Energy’ drinks e.g. Red Bull, Powerade






Chocolate bar

5.5-21mg per 50g bar

Chocolate mousse

2-5g per 100g


You should avoid:


  • Foods which may increase the risk of listeriosis:
  • Soft ripened cheese such as camembert, brie, and goats’ and sheep’s milk cheeses. Care must also be taken with mould-ripened cheese. Hard cheeses, yogurts and butter are safe because of their low pH and lack of moisture, and processed cheeses and cottage cheeses are likely to be free of the bacterium too.
  • Unpasteurised milk (from cows, sheep or goats) and any products made from it.
  • Pre-cooked or ready prepared cold foods which will not be re-heated, e.g. purchased salads, quiches, and meat pies eaten cold.
  • Liver and liver products, to avoid excess consumption of vitamin A.
  • Supplements containing vitamin A or fish liver oils, unless medically advised.
  • Shark, swordfish and marlin due to high levels of mercury.
  • Peanuts or peanut products if you or a close relative have a history of atopy (allergy).




During pregnancy, iron is needed for the manufacture of haemoglobin in red blood cells both in the mother and baby. The baby accumulates most of their iron during the last trimester (last 3 months). If you become iron deficient (anaemic) during pregnancy, this won’t usually mean that your baby is born anaemic.


The current Dietary Reference Value (DRV) for iron in an adult female is 14.8mg/day with no recommended increase during pregnancy, as your body adapts to this situation through a number of combined actions:

  1. Your body’s stores of iron are ‘mobilised’.
  2. You absorb more iron from your food than when not pregnant.
  3. You lose less iron because you are not menstruating.


When it comes to iron in food, it is more important where you get the iron from than the amount of iron. “Haem iron” (from animal sources such as meat and fish) is absorbed more efficiently, whereas “non-haem iron” (from non-animal sources such as fortified breakfast cereals, pulses and green leafy vegetables) is affected by a number of other dietary factors that can inhibit or increase its absorption:

  • Vitamin C increases
  • Calcium and polyphenols such as tannins from tea and eggs inhibit


Therefore, you should aim to include lean meat within your diet every day. If you are vegetarian/vegan, try to consume some form of vitamin C at every meal. Avoid drinking tea with meals or taking your calcium supplements directly before a meal.


Particularly good sources of vitamin C include:

  • Oranges and orange juice (limit juice to 100ml daily)
  • Red and green peppers
  • Strawberries
  • Blackcurrants
  • Broccoli
  • Brussels sprouts
  • Potatoes




Throughout pregnancy your body has increased requirements of this vitamin. This can be achieved by ensuring adequate supplementation (see recommendations below) and a well balanced diet containing folate-rich foods:

  • Green leafy vegetables
  • Granary bread
  • Pulses (lentils & beans)
  • Yeast extract e.g. Marmite, Vegemite
  • Fortified breakfast cereals
  • Milk – choose skimmed, 1% fat or semi-skimmed
  • Tomato and orange juice (limit to 100ml daily)
  • Eggs




During the first 12 weeks of pregnancy, you are advised to avoid vitamin and mineral preparations which contain vitamin A in the retinol form as retinol may increase the teratogenic risk. This means the growth and development of the foetus could be disturbed. There are vitamin and mineral supplements containing no vitamin A which are specifically aimed at preconception and pregnancy; these also contain the additional folic acid that is required during pregnancy e.g. Pregnacare, Seven Seas Pregnancy and Centrum Pregnancy Care. If you choose one of these, you must take it twice daily. If you take Forceval (the multivitamin & mineral supplement available on prescription), you can continue to do so as the vitamin A contained within it is not in the retinol form.


You need to take additional folic acid prior to conception and for the first trimester (12 weeks) of pregnancy because there may be an increased risk of a neural tube defect-affected pregnancy. 


The amount you need to take depends on your BMI:

  • Over 30kg/m2: an additional 5mg of folic acid per day. This is recommended for all obese women, not just those who have had weight loss surgery.
  • Under 30kg/m2: an additional 400µg of folic acid per day.


You should continue taking your calcium and vitamin D and iron supplements as described in Section 14 – but remember to take these at least 2 hours apart to enhance absorption.


If you are receiving vitamin B12 injections or taking vitamin B12 tablets, it is fine to continue having these.




You will undergo regular monitoring with your midwife. In line with the guidance from BOMSS, we advise blood tests to take place every trimester to include ferritin, folate, vitamin B12, calcium and fat soluble vitamins (A, D, E and K).


If you are being tested for gestational diabetes, it is advisable not to have an Oral Glucose Tolerance Test (OGTT) as it increases the risk of dumping syndrome or reactive hypoglycaemia. The recommendation is to use fasting or 2-hour post-prandial (after a meal) glucose instead. Your midwife and/or GP will be able to discuss these options with you.




The more active and fit you are during pregnancy, the easier it will be for you to adapt to your changing shape and weight gain. It will also help you to cope with labour and help you get back into shape after the birth.


Keep up your normal daily physical activity or exercise (sport, running, yoga, dancing, or even walking to the shops and back) for as long as you feel comfortable. Exercise is not dangerous for your baby – there is some evidence that active women are less likely to experience problems in later pregnancy and labour.


Exercise tips for pregnancy:


  • Don’t exhaust yourself. You may need to slow down as your pregnancy progresses, or if your maternity team advises you to.
  • If you weren't active before you got pregnant, don’t suddenly take up strenuous exercise. Remember that exercise doesn't have to be strenuous to be beneficial.
  • Drink plenty of water and other fluids.
  • If you go to exercise classes, make sure your teacher is properly qualified, and knows that you’re pregnant as well as how many weeks pregnant you are.


Weight gain


There are no formal evidence-based guidelines from the UK Government or professional bodies on what constitutes appropriate weight gain during pregnancy. According to the Institute of Medicine (USA) guidelines produced in 2009, acceptable weight gain during pregnancy is as follows, depending on pre-pregnancy BMI:


Pre pregnancy BMI


Total weight gain range

Rates of weekly weight

gain in the 2nd and 3rd


<18.5 (underweight)

2st 0lb (12.7kg) to 2st 12lb (18.1kg)

1lb (0.5kg) to 1.3lb (0.6kg)


18.5 – 24.9 (healthy)

1st 11lb (11.3kg) to 2st 7lb (15.9kg)

0.8lb (0.4kg) to 1lb (0.5kg)


25.0 – 29.9 (overweight)

1st 1lb (6.8kg) to 1st 11lb (11.3kg)

0.5lb (0.2kg) to 0.7lb (0.3kg)


≥30.0 (obese - includes all classes)


11lb (5kg) to 1st 6lb (9kg)

0.4lb (0.18kg) to 0.6lb (0.27kg)



Gaining more than the amount stipulated above is not beneficial to the baby, and is likely to contribute towards you being unable to get back to a healthy weight post-pregnancy. Based on this, the common phrase ‘eating for two’ is not true. No extra calorie requirements are advised during the first 2 trimesters (first 6 months) and only an additional 200 calorie increase is recommended during the final trimester (3months). The best advice is to eat according to appetite and monitor your weight gain.



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