Embryo to Fetus to Birth 1-3 Trimesters Development Embryo to Fetus to Birth 1-3 Trimesters

Neurula Day 28 2-3.5 mm

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 http://www.cnn.com/2015/02/25/health/rare-en-caul-birth-amniontic-sac/

Umbilical cord Placenta Umbilical cord: holds baby to the mother at the site of the placenta. Placenta: on the surface of the uterus and is where diffusion of food, oxygen, carbon dioxide and waste takes place

The umbilical cord contains two arteries and a vein The vein carries blood to the baby The arteries carry blood 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

Sex of the baby can be determined Nails and earlobes develop 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

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

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

end of 2nd 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

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

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 Interrupts 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