The growth of your baby is a continuous process that often conveys a sense of awe. The following information is divided into pregnancy’s three trimesters to help you understand your baby’s rapid growth. Milestones in fetal development are also highlighted. (Sizes and weights are approximate.)
At the end of four weeks:
- Baby is 1/4 inch long.
- Heart, digestive system, backbone and spinal cord begin to form.
- Placenta (sometimes called "afterbirth") begins to develop.
- The single fertilized egg is now 10,000 times larger than it was at conception.
At the end of 8 weeks:
- Baby is 1-1/8 inches long.
- Heart is functioning.
- Eyes, nose, lips, tongue, ears and teeth are forming.
- Penis begins to appear in boys.
- Baby is moving, although the mother can not yet feel movement.
At the end of 12 weeks:
- Baby is 2-1/2 to 3 inches long.
- Weight is about 1/2 to 1 ounce.
- Baby develops recognizable form.
- Nails start to develop and earlobes are formed.
- Arms, hands, fingers, legs, feet and toes are fully formed.
- Eyes are almost fully developed.
- Baby has developed most organs and tissues.
- Baby's heart rate can be heard at 10 weeks with a special instrument called a Doppler.