The popularity of the keto diet for weight management is at an all time high in the community, and some people are getting good results in the short term. But is the keto diet safe if you are pregnant, or actively trying to get pregnant?

Firstly I think it is good to define what we are meaning by the keto diet. This will obviously vary depending on the regime, but what I have typically seen in the popular media is a diet where about 5-10% of calories or energy in the diet come from carbohydrates and the rest from fats and protein. There are a lot of places calculating macros for keto diet and spitting recommendations of eating about 20-30g of carbohydrate per day. This is a very severe restriction, much more so then other lower carbohydrate or modified carbohydrate diets which have been researched in the context of gestational diabetes in pregnancy, which have set a low carbohydrate diet at about 40% of energy from coming from carbohydrate, and the rest from protein and fats. Even this more moderate restriction of carbohydrate in gestational diabetes has been questioned in recent times with good outcomes found for women with gestational diabetes in women who had a more liberal intake of carbohydrate, when those carbohydrates come from high quality, low GI, unrefined sources.      

As for Keto there is no research indicating the safety or otherwise of the keto diet in human pregnancy. But there is strong the theoretical reasons and animal studies that indicate following a keto diet when pregnant or if actively trying to become pregnant could cause major harm, mainly in terms of outcomes for the unborn child.

First up is the concerns for nutritional adequacy and the dire consequences of inadequate intake of nutrition on the unborn baby. The level of restriction of carbs in the typical keto diet is severe- two pieces of fruit would typically see you meet or exceed your limit. But carbohydrates are found in many healthful foods, we have already mentioned fruit, but also milk and milk alternatives, vegetables- most people think of potato, sweet potato and corn when they consider high carb veggies, but to achieve the very low level of carbs recommended in these keto diets, many followers are also restricting foods such as carrot, beetroot, parsnip, pumpkin, peas, and others, then there is obviously grain and grain foods, including low GI nourishing whole grains such as quinoa, chia seeds, oats and barley; as well as lentils, legumes and beans, and even nuts have some carbohydrate. These foods contribute to an enormous range of micronutrients and fibre for the body. And when you don’t supply your unborn baby with a balanced diet with the full range nutrients you are placing them at increased risk of developing a range of birth deformities, disabilities, decreased cognitive capacity, and increased risk of behavioural and mental health issues in the longer term. This is not something to muck around with!!!!! A recent study in the USA has already pointed to increased prevalence to neural tube defects which has been linked to the rising popularity of low carb diets in the community. Other researchers have found excessive dietary restriction, and weight loss in pregnancy has is linked to miscarriage, small for gestational age babies, and preterm birth.  

Evidence from animal models in mice and rats that show a keto diet is linked with some pretty horrible outcomes. Specifically retarded growth, changed structure and relative size of various components of the brain, and decreased size of other organs in the body occurred when the mums were fed a ketogenic diet in pregnancy, compared to those whom had a mother fed a standard diet. Additionally one of the mice studies followed the mice to adulthood, those who had been exposed to a keto diet in-utero where more likely to exhibit anxiety and depression. Now humans are not mice or rats but animals models have been used in science and medicine for many years, for a very good reason- ideas for new treatments are tested in animals, and it is not until they are found safe in this environment that they can then be tested in humans. Another study which looked at diet restriction in-utero (not specifically keto) and effects of adults rats, it also showed increased tendency to anxiety and also increased weight gain and fat stores. At this stage of nutritional science it would be completely unethical to study the effects of the keto diet in human pregnancy, when the outcomes in animals have been so dire.

The effect of the restrictive diet in-utero on adult rat metabolism reminds me of the effect of generalised malnutrition during human pregnancy. There is lots of research on the Barker Hypothesis, which shows malnutrition in-utero and small birth size (as has occurred in various famines due to war or poverty), is associated with numerous adult ‘lifestyle’ diseases in the offspring including increased obesity, type 2 diabetes and cardiovascular disease. Given the restrictions imposed on the keto diet, I think it would be common for women following these diets to not meet their caloric needs in pregnancy, and they may not gain the correct amount of weight recommended based on their pre pregnancy BMI. It seems the balance between under and over nutrition is important, with both side of this continuum in pregnancy linked to poor birth outcomes and longer term health outcomes for the offspring.   

So what do you do if you have been following a keto type diet, for weight loss or management of conditions like PCOS and you now want to become pregnant?  You maybe even a little bit scared of eating a full range of carbohydrates again, given the benefits you have found your body on this diet? It’s tricky I know, but I think the potential for harm to your baby, outweigh any benefits you have seen in your own body to date. But don’t stress, NO ONE is going to tell you to get stuck back into the sugar and refined white baked goods. I think it is best to talk to your doctor and a clinical dietitian to help you make some changes to your diet to ensure nutritional adequacy for (fingers crossed) your soon to be baby, and work on finding a more balanced diet which will still work in managing your own health conditions. I think the focus would be on gradually re-introducing high quality, low GI, unrefined carbohydrates, and completing nutritional screening tests to ensure your body is ready to carry a pregnancy before you try to conceive.  

References:

De Boo, Hendrina A., and Jane E. Harding. “The developmental origins of adult disease (Barker) hypothesis.” Australian and New Zealand Journal of Obstetrics and Gynaecology 46.1 (2006): 4-14.

Desrosiers, Tania A., et al. “Low carbohydrate diets may increase risk of neural tube defects.” Birth defects research110.11 (2018): 901-909.

Goldstein, Rebecca F., et al. “Association of gestational weight gain with maternal and infant outcomes: a systematic review and meta-analysis.” Jama 317.21 (2017): 2207-2225.

Kapadia, Mufiza Zia, et al. “Weight loss instead of weight gain within the guidelines in obese women during pregnancy: a systematic review and meta-analyses of maternal and infant outcomes.” PloS one 10.7 (2015): e0132650.

Sussman, Dafna, et al. “Effects of a ketogenic diet during pregnancy on embryonic growth in the mouse.” BMC pregnancy and childbirth 13.1 (2013): 109.

Sussman, Dafna, Jacob Ellegood, and Mark Henkelman. “A gestational ketogenic diet alters maternal metabolic status as well as offspring physiological growth and brain structure in the neonatal mouse.” BMC pregnancy and childbirth 13.1 (2013): 198.

Sussman, Dafna, Jurgen Germann, and Mark Henkelman. “Gestational ketogenic diet programs brain structure and susceptibility to depression & anxiety in the adult mouse offspring.” Brain and behavior 5.2 (2015): e00300.

Ramírez-López, María Teresa, et al. “Maternal caloric restriction implemented during the preconceptional and pregnancy period alters hypothalamic and hippocampal endocannabinoid levels at birth and induces overweight and increased adiposity at adulthood in male rat offspring.” Frontiers in behavioral neuroscience 10 (2016): 208.

Hernandez, Teri L., Archana Mande, and Linda A. Barbour. “Nutrition therapy within and beyond gestational diabetes.” Diabetes research and clinical practice (2018).

Hernandez, Teri L. “Carbohydrate content in the GDM diet: two views: view 1: nutrition therapy in gestational diabetes: the case for complex carbohydrates.” Diabetes Spectrum 29.2 (2016): 82-88.

Yamamoto, Jennifer M., et al. “Gestational diabetes mellitus and diet: a systematic review and meta-analysis of randomized controlled trials examining the impact of modified dietary interventions on maternal glucose control and neonatal birth weight.” Diabetes Care 41.7 (2018): 1346-1361.