Development Embryo to Fetus to Birth 1-3 Trimesters

Day mm Neurula

Amniotic Sac Originally forms around the embryo Eventually fills with liquid provided by the mother’s cells Later, formed by the fetal kidneys Circulates when the baby drinks the liquid and excretes it out

Amniotic Sac Some babies are born inside the amniotic sac 1 in 80,000 births

Umbilical cord Placenta Placenta: holds baby to the mother Diffusion of food, oxygen, carbon dioxide and waste takes place

Umbilical cord contains an artery and a vein One carries things to the baby One carries things away from the baby

4 weeks Brain is formed Heart is beating Eye, legs,arms begin 1/6 inch

6 weeks ½ inch Circulation begins Toes and fingers forming

8 Weeks  Eyes, nose, lips, tongue, ears and teeth are forming  Gonad formation begins  Functioning heart  Now considered FETUS 1.2 inches

12 Weeks 2.5 – 3 inches and.5 – 1 oz. Sex of the baby can be determined Nails and earlobes develop Eyes almost fully developed All parts present, now major GROWTH and DEVELOPMENT

2 nd Trimester Placenta fully developed Fetus can hear mother Vernix forms – creamy white substance that protects thin skin Week 13 to Week 27

2 nd Trimester Skin is reddish and forms lanugo (downy hair) Reflexes: swallow, suckling, jumping

end of 2 nd trimester: 15 inches long 2.5 pounds Sleep – wakefulness cycles Fat forms lungs are beginning to exhale amniotic fluid (practice for breathing) circulatory system working

3 rd Trimester Fetus has sight and hearing Soft skeleton Laguno disappears – skin begins pigmentation Circulatory and Respiratory systems mature Week 28 to Week 40

Mother’s antibodies pass to fetus Digestive organs expel wastes- meconium Baby moves downward towards birth canal

Parturition (Birth) Expel fetus from uterus = LABOR Last few weeks of pregnancy, estrogen levels peak: – myometrium forms oxytocin receptors – Interupts progesterone, allows small uterine contractions (false labor, Braxton Hicks) Oxytocin production causes placenta to release prostaglandins = more powerful contractions

Positive Feedback Loop Hypothalamus activated by increasing pressure levels on the cervix Activates pituitary to release more OXYTOCIN…

Three Stages of Labor: DIALATION True contractions dilates cervix 1 to 10 cm Contractions – Increase from weak to vigorous – Regular – Upper uterus downwards to birth canal – Soften cervix: effaces – 6-12 hours

Three Stages of Labor: EXPULSION Delivery of infant out of vagina Mother’s response is to push Infant is facing downwards: vertex, if butt down: breech Mucus is suctioned before full delivery – baby begins to breathe Complications (dropping oxygen levels or heart rate in infant) overcome by forceps, vacuum or Cesarean section

Three Stages of Labor: PLACENTAL Uterine contractions compresses blood vessels Placenta detaches Afterbirth = placenta, fetal membranes and umbilical cord Need to remove all tissues – could cause excess bleeding

Thank your mother… Uterus stretches to occupy most abdominal cavity Estrogen/progesterone surge (morning sickness) Ribs flare (shortness of breath, but vital capacity increases) Lordosis – lumbar curvature (back aches) Relaxin causes pelvic ligaments and pubis to widen/relax (duck walk) Organ displacement = pressure on esphogus, stomach, and intestines (heartburn, small meals, constipation) Excess waste from fetus and limited room (frequent urination…uncontrollable) Blood volume increases up to 40%, blood pressure and pulse rate increases (swelling = edema)