Your baby resembles a tadpole more than a human, but is growing fast. The circulatory system is beginning to form, and the tiny heart will start to beat this week. Your baby is the size of a sesame seed. Read about your pregnancy at 5 weeks.
Stores of B12 can last for up to a year. Foods high in Vitamin B12 include shellfish, liver, fish, crab, fortified soy products (tofu, soymilk), fortified cereals, red meat, low fat dairy, cheese, and eggs.
The usual dietary sources of Vitamin B 12 are animal-derived foods, although a few plant-based foods contain substantial amounts of Vitamin B 12. To prevent Vitamin B 12 deficiency in high-risk populations such as vegetarians, it is necessary to identify plant-derived foods that contain high levels of Vitamin B 12.