Week 1 (0 to 7 days)
- Conception: dad’s sperm penetrates a mom’s oocyte (egg) in the fallopian tube. A new, unique, never-to-be-repeated human being begins the first day of life as a single cell embryo (zygote).
- Baby is smaller than a grain of sugar, but a complete DNA / genetic blueprint is already present for all the tiny person will become. All inherited physical features are already set – eye, hair and skin color, fingerprints, gender, height, shape of the face and body, dimples, elements of personality, various intelligences, etc.
- Baby’s cells continually divide. Each will perform different functions – circulatory, muscular, neural, skeletal, etc.
- Baby is traveling down the fallopian tube toward the uterus to find the food and shelter needed to grow and develop.
Week 2 (8 to 14 days)
- Baby is about the same size as the period at the end of this sentence and growing exponentially.
- Implantation is completed – baby snuggles into the wall of the mom’s womb and begins to draw nourishment.
Doctors can detect pregnancy as early as 8 or 9 days after fertilization. Most moms, however, have no idea they are pregnant for several weeks. (It is at this point that mom misses her first period, but often she may experience “implantation bleeding” which can mimic a light period.) Sensitive pregnancy tests can be positive, but it depends on the level of hormone (hCG) produced by the baby. Usually by the time mom discovers she is pregnant, many important structures in the growing embryo have long since developed.
Week 3 (15 to 21 days)
- Baby’s sex cells that will become sperm / eggs for creating grandchildren begin to group together.
- Foundations of baby’s brain, spinal cord, heart and central nervous system are being established.
- Baby’s heart has begun to beat – first organ to function, no bigger than a poppy seed, initially beating at 70 times per minute, and visible by ultrasound almost immediately.
- Blood vessels begin to form.
- Eyes and ears begin to develop.