Fetal Development

First trimester—months 0-3 Second Trimester–months 4-6 Third Trimester—months 7-delivery

Week 2 Embryo is about 1.5 millimeters long Neural plate appears

Week millimeters long Has somites (embryonic body segments) Blood vessels and primitive gut begin to develop Begins Most critical weeks of development

Week millimeters long Increases mass 7,000 times Eyes begin forming Heart is still a tube but it begins to flutter and pulsate Neural groove closes Embryo is C-shaped Now has 30 pairs of somites Muscles, bones, and connective tissue develops from somites Arm buds are visible and leg buds begin to form By end of week 4, heart develops into four chambered vessel

Month 2 Embryo increases in mass 500 times and weighs about 1/30 ounce (1 aspirin) About 1 inch long After 2 months, called a fetus Arms, legs, knees, elbows, fingers, and toes begin to form There is a temporary tail that is longest at this time but gradually disappears. Gone in 94% of babies by time of birth. Liver is now about 10% of body and is the main blood forming organ Diseases my effect development such as German measles which affects heart formation, the eye lens, the inner ear, and brain

Month 3 Around 3 inches long from head to buttocks and weighs about ½ ounce (15 aspirins) Fetus is able to move arms and kick legs Has reflexes like squinting, frowning External sexual organs begin to develop Can suck and swallow some of the fluid that surround the amniotic sac Kidneys and the other excretory structures develop Waste is disposed thru placenta

Month 4 5 inches long (head to buttocks) and weighs 5 ounces Bony skull is forming and can be seen by X-ray The body is becoming covered by protective, cheesy coating

Month 5 7 inches long and weighs ½ lbs. or 8 ounces Has hair on head Body is covered by fuzzy soft hair called lanugo Heart beats times /minute Youngest child to survive was 23 weeks but required assisted breathing, feeding, temperature maintenence

Month inches long and weighs 1.5 lbs. 90% of fetal weight gain occurs during this time At end of 6 months, a fetal typically has a good chance of survival Skin is red and wrinkled Abundant cheesy body covering Can now find pasty green mass of dead cells and bile called meconium in bowel which stays until birth Problem: if released early, child is exposed to bacterial infection especially in lungs eyes and eyelashes appear

Months 7-9 Doubles in size Many nerve tracts are forming and new brain cells are produced at rapid rates Protein intake by mother is important because protein is needed to develop the nervous system affecting intelligence At months 8-9 fat is deposited which smoothes out the wrinkles Nails project Hair coat sheds