Pregnancy and Bariatric Surgery

Falling Pregnant after Weight Loss Surgery

By Kishani Turner
Bariatric Dietitian

Obesity is associated with reduced fertility and conception can be difficult with oligoovulation (irregular/ infrequent ovulation resulting in 8 or less periods a year) or anovulation (absence of ovulation) common in PCOS.

Some people undertake bariatric surgery to assist fertility and /or increase the likelihood of a healthy pregnancy.

Rapid weight loss and hormonal changes that occur with weight loss surgery may result in increased fertility, even if you have had difficulty conceiving previously. It is important to take the necessary precautions so as to not find yourself pregnant too early/ unexpectedly. It is often recommended to commence contraception prior to bariatric surgery.

Conceiving prior to 1 year following weight loss surgery is not advised as weight has not stabilised and the effects on nutrition status have not been realised. This may increase the risk to the baby and mother.

If you think about it – your body is recovering from major surgery, losing weight and trying to meet its nutritional needs AND then it needs to grow or support another life. This increases the risk of not meeting your own nutritional needs and also that of your baby, or other complications such as low birth weight for the child, C- section and weight gain.

Expected Weight Gain:

The current recommendations for weight gain in pregnancy following weight loss surgery, is based on that of a non-bariatric pregnancy weight gain, which is 11.5- 16kg for a healthy weight range (BMI 19-25) at conception.

If pregnancy occurs whilst the mother is above their healthy weight range (which is likely to be the case if pregnancy occurs prior to 1 year post bariatric surgery) then the expected weight gain is adjusted.

  • People undertake bariatric surgery in order to lose weight, so gaining weight following bariatric surgery can be counterintuitive or a source of stress, especially as many women’s weight journey has involved significant weight gain within pregnancies and difficulty losing their baby weight.
  • It can be helpful to understand what contributes to the weight gain in pregnancy.
  • You can expect to gain 1-1.5kg in the first trimester and then 1.5-2kg each month until you give birth.
  • This weight comes from the placenta, increased blood volume and a growing baby.

It is important to remember that the weight gain is natural and focus on the health of you and your baby. If you experience any challenges with body image as your body goes through significant change, remember you can see your psychologist and/ or dietitian.

Insufficient weight gain during pregnancy leads to an increased risk of:

  • Low birth weight for the infant
  • Preterm birth

Nutritional Requirements:

Vitamin and mineral deficiencies can occur anytime after weight loss surgery. It is important to have your bariatric screening bloods checked prior to conception or as close to as possible, and then every trimester – more frequently if you are deficient in any nutrient/ or a deficiency is being corrected.

It is a common misconception that pregnant women need to “eat for two” and this is often what leads to excessive weight gain. Women don’t need to ‘eat for two’ but they do need to eat twice as well. With only a 15–25% increase in requirements for energy (kilojoules), the quality (not so much the quantity) of dietary intake becomes important to meet increased nutrient needs. Keep in mind, this is in addition to after bariatric surgery, where your uptake or absorption of nutrients is altered and your capacity for food is about 1 cup.

So good nutrition during a bariatric pregnancy is especially about the quality of food eaten rather than the quantity.

Choosing a wide variety of foods from each food group will help to meet the extra demands, however it may be necessary to focus more on:

  • Lean meat, chicken, fish and non-meat alternatives such as dried beans, lentils, tofu and cooked eggs
  • Nuts and seeds
  • Reduced-fat milk, cheese and yoghurt
  • Green leafy vegetables.


We need more protein during times of cell growth / repair such as is in pregnancy and lactation, therefore it is important to see your dietitian to check the adequacy of your intake and discuss supplements if necessary.


Pregnant women require more water to support feral circulation, amniotic fluid and a higher blood volume. Fluid need is 750–1,000mL per day above the usual daily recommendation of 2.0L per day. Keeping in mind, you do not want to drink with your meals and until 30 minutes after, meaning between meals are your opportunity. Some people continue to find water “heavy” after bariatric surgery making achieving their target a challenge. Please see your bariatric dietitian for strategies.

Vitamins/ Minerals:

Following weight loss surgery, vitamins and minerals are at nutritional risk due to reduced intake and/ or altered absorption, therefore it is recommended to take supplements life-long.

Pregnancy itself has an increased requirement for vitamins and minerals and food intake can be reduced due to morning-sickness. It is important to discuss your need for supplementation with your bariatric team.

Folate supplements are recommended to be taken two months before you fall pregnant and for the first three months of pregnancy, to reduce the risk of spinal problems such as Spina Bifida in your baby.

Iron is needed to make red blood cells which carry oxygen around the body.

During pregnancy you need more iron because the volume of your blood increases and your baby’s blood is also developing (a developing fetas draws its iron from the mother to last it through the first 5-6 months after birth). It is important for pregnant women to eat iron-rich foods every day, such as meat, chicken, seafood, dried beans and lentils, and green leafy vegetables. Iron from plant sources is not as easily absorbed and becomes an added challenge if you are vegetarian which you can discuss with your bariatric dietitian.

Vitamin D is important for the development of your baby’s bones and teeth. Low levels can cause muscle weakness and pain in women. Vitamin D is mostly made in the skin by the action of sunlight. You may be deficient if you:

  • Spend most of your time indoors
  • Cover most of your body with clothing or sunscreen
  • Have darker skin

Calcium requirements during pregnancy and breast-feeding remain unchanged to the daily requirement of non-pregnant women. Although the baby has a high requirement for calcium in the third trimester when it starts to develop and strengthen its bones, the mother has an increased ability to absorb dietary calcium. However, following weight loss surgery, dietary calcium absorption is altered so supplementation is necessary in additional food sources such as dairy and calcium fortified alternatives such as soy.

Iodine requirements are increased during pregnancy and breastfeeding. Iodine is an essential vitamin for brain development and the nervous system. Iodine supplementation is recommended for women planning pregnancy, throughout pregnancy and whilst breast- feeding. Women with pre-existing thyroid condition should seek advice from their doctor before taking an iodine supplement.

Thiamine (Vitamin B1) is an essential B group vitamin as the body cannot produce it, so it must be eaten from various thiamine- rich foods (meat, nuts and wholegrain cereals). Decreased nutritional intake, impaired absorption and increased loss (all of which occur with weight loss surgery) are risks for thiamine deficiency. Significant vomiting or vomiting over a prolonged period, as can occur with severe morning sickness, can increase the risk of thiamine deficiency and needs close monitoring by your bariatric team, obstetrician or GP.

Additional Information:

Gestational Diabetes: The OGTT (Oral Glucose Tolerance test) usually administered at 24 weeks gestation may be poorly tolerated and / or may trigger severe dumping. It is important you tell your obstetrician and GP that you have had weight loss surgery. Alternative screening options may need to be considered eg: fasting blood glucose, HbA1c and self-monitoring of blood sugar level via finger prick (pre and post meal for 1 week) so discuss this with your obstetric team.

Listeria: is a risk in any pregnancy. Some of the “at-risk foods” are great protein sources enjoyed after weight loss surgery to ensure adequate protein intake. Avoiding these may make achieving your protein goals challenging so speak with your bariatric dietitian.

  • Reduce the risk of listeria infection by eating foods that have been freshly cooked or prepared
    • Avoid:
      • Buffets, salad and sandwich bars
      • Meats which are raw or undercooked, cold deli meats, packaged/ready-to-eat meats including cooked cold ready-to-eat (unless reheated until steaming hot)
      • Pre-packaged or pre-prepared fruits and vegetables
      • Chilled seafood eg. raw oysters, sashimi, sushi and cooked, chilled prawns or smoked salmon
      • Soft cheeses like brie, camembert, feta and ricotta
      • Unpasteurised milk products and juices
      • Refrigerated pâté, meat spreads or smoked seafood
      • Raw or undercooked eggs.
      • Avoid raw sprouts
  • Rinse fresh fruits and vegetables in running water before preparing
  • Follow safe food handling practices including washing hands, food preparation surfaces and utensils thoroughly

Pregnant and breastfeeding women are encouraged to continue eating fish and seafood (keeping in mind the tips above) as they are a great source of omega 3 fatty acids and protein. Seafood is often one of the protein sources that are well tolerated after bariatric surgery, however, large, deep-sea fish can contain high levels of mercury. The mercury from these fish may affect the developing nervous system of unborn babies and infants.To reduce the risk of birth defects, pregnant women should limit their intake of fish high in mercury:

  • Shark (flake), broadbill, marlin and swordfish should only be eaten once per fortnight with no other fish during that fortnight
  • Orange roughy (sea perch) and catfish should be eaten no more than once per week, with no other fish that week
  • Two to three serves per week of any other fish not mentioned above may be eaten safely.


Healthy Eating is an important part of living a healthy life, even more so in living a healthy life after weight loss surgery and vital if you’re pregnant or planning pregnancy after bariatric surgery. Ensure you engage with your bariatric team to get specialised support.


Are you ready to find out more?

Call us today for a complimentary 30-minute consultation with our Bariatric Nurse Educator or one of our Bariatric coordinators.