At 5 weeks pregnant, baby is the size of an apple seed. Your embryo is now measurable. Baby is now gearing up for much more growth.br br During week 5 of pregnancy changes in your body are still subtle and your baby is still tiny. This is the time when many pregnant women start to experience their first pregnancy symptoms as a result of hormonal changes.br br At week 5 you are supposed to gain weight. Your doctor will discuss about your weight gain based on your body type.br br Various hormones are circulating throughout your body to maintain and support your pregnancy:br br 1. Human Chorionic Gonadotropin (HCG): This hormone helps in the nourishment of your baby. It is also responsible for maintaining adequate levels of progesterone.br br 2. Progesterone: It is not only responsible for maintaining placental function but it is also responsible for inhibiting uterine contractions and stimulating breast tissue growth.br br 3. Estrogen: This hormone is produced to maintain progesterone and HCG levels.br br Baby's development:br br Your baby is growing at a rapid pace with several cell types and organs starting to develop, including the blood cells, kidney cells, nerve cells, brain, spinal cord, heart and gastrointestinal tract.