Conception Day The egg and sperm most often unite in the fallopian tube (tube from the ovary to the uterus) to form a single cell called a zygote. The zygote contains 46 chromosomes, 23 chromosomes from each parent. This tiny new cell, smaller than a grain of salt, contains all the genetic information for every detail of the new created life - the color of the hair and euyes, the intricate fine lines of the fingerprint, the physical appearance, the gender, the height and the skin tone. this new life is now called an embryo.
Day 2-5 (after conception) The embryo begins to implant in the lining of the uterus on about day 6. Once this occurs, hormones trigger the mother's body to sustain the pregnancy and prevent her monthly periods. The embryo around day 8 is about the size of the "period" used in this sentence (or 0.1mm).
Day 6-10 (after conception) The embryo begins to implant in the lining of the uterus on about day 6. Once this occurs, hormones trigger the mother's body to sustain the pregnancy and prevent her monthly periods. The embryo around day 8 is about the size of the "period" used in this sentence (or 0.1mm).
Week 4 By now, the embryo is completely attached to the lining of the uterus. There is enough of the pregnancy-specific hormone (hCG) circulating in the mother's blood to give a positive pregnancy test.
Week 5 The foundation for every organ system is already established and beginning to develop. At this age, the first signs of brain development are evident, the ribs, vertebrae and muscles begin to form. The developing lungs are evident, and the heart, about the size of a poppy seed, is the first organ to function. The beating heart can be seen on ultrasound.
Week 6 At this stage, the origin of the entire central nervous system (brain and spinal cord) is laid down. Eye formation, the jaws and upper limb buds are now visible. By the end of week 6, the lower limb buds can also be seen.
