Is the ketogenic diet safe during pregnancy?

The ketogenic diet is not currently recommended during pregnancy. Studies done in mice and rats have shown that ketosis could negatively affect the growth of the fetus. These rodent studies showed some neurodevelopmental delays, low birth weights, and abnormal organ development.^[1][2] A study done on mice also showed that a ketogenic diet decreased the viability of the embryo after implantation, which might mean an increased risk for miscarriage.^[3] In one study it was noted that there was improvement in these abnormalities if the mother was given a normal diet at a later stage in the pregnancy and during lactation.^[1] All of these studies have been done in rodent populations, so they cannot be translated directly to human pregnancy. However, given the concerning findings, it is not considered safe to follow a ketogenic diet during pregnancy.