Your First Trimester
Fetal Development
At the end of four weeks:
- Embryo is 1/4 inch in length
- Heart, digestive system, backbone and spinal cord begin to form
- Placenta (sometimes called "afterbirth") begins developing
- The single fertilized egg is now 10,000 times larger than size at conception
At the end of 8 weeks:
- Embryo is 1 1/8 inches in length
- Eyes, nose, lips, tongue, ears and teeth are forming
- Penis begins to appear in boys
- Embryo is moving, although the mother can not yet feel movement
- Heart is functioning
At the end of 12 weeks:
- Fetus is 2 1/2 to 3 inches long
- Weight is about 1/2 to 1 ounce
- Nails start to develop and earlobes are formed
- Fetus develops recognizable form
- Arms, hands, fingers, legs, feet and toes are fully formed
- Eyes are almost fully developed
- By this stage, a fetus has developed most of his/her organs and tissues
- Fetal heart rate can be heard at 10 weeks with a special Doppler instrument