Many of the most dramatic prenatal developments occur during the first couple weeks ofpregnancy.There are three periods of prenatal development (these are NOT the same as the trimesters)1. Period of the zygote begins with conception (when the egg is fertilized in the fallopiantube) until the newly merged sperm and egg are implanted in the uterine wall, about12-14 days post-conception. Once it sticks to the wall, it is an embryoa. The new mass of cells starts dividing quickly and quickly forms a little ball of cellsknown as blastocyst. About 4 days after conception, there should be 100 hollowcells in the blastocystb. The cells are totipotent, meaning they contain a germ disk (the cells thatactually become the baby’s body)c. Other germ disks go into the placenta, the support structure2. Period of the embryo begins just after implantation and continues until a recognizableorganism has formed (about 8 weeks)a. There are three layers of pluripotent / undifferentiated cells, meaning theycould be any part of the embryo.❖ Ectoderm becomes hair skin and nervous system, innermost❖ Mesoderm becomes hair and bones, middle❖ Endoderm becomes lungs and digestive system, innermostb. Eventually they become differentiated / unipotent meaning they specialized inone type of cell, not manyc. The embryo grows inside-out (proximodistal) and head-to-toe (cephalocaudal),which is why the head is so fucking big3. Period of the fetus begins at 9 weeks once all major organs are fully formed.a. The placenta has differentiated into the chorionic villi (which separates themother’s blood from the babies blood), the umbilical cord (which connects thefetus to the placenta) and the amniotic sac (a salt-water bag that cushions thebaby from harm).b. Placental barrier is where all food, nutrients and toxins pass throughc. Cerebral cortex, fingernails and sex-specific partsd. Fetus is covered in a waxy substance called vernix which prevents the fetusfrom chappingABC’s of childbirth:1. Amniotic sac breaking (water breaking, only in 20% of cases, and fecal matter happenswith it)2. Blood around the vagina3. ContractionsStages of childbirth1. Stage 1 (12-24 hours) is the contraction period, where we need to get contractions to 10cm2. Stage 2 (1 hour) is the actual childbirth. This is most risky: if the placenta detachesbefore the birth, it can choke the baby (leading to anoxia, lack of oxygen), and a 20%chance of c-section occurs here3. Stage 3 (10-15 min) is the afterbirth, which is short but necessary where the babysupport structure is ejectedMany diseases (AIDS, syphilis, Rubella, genital herpes, etc.) that target the placenta and theheart, so if the mom has it the child mightAmniocentesis = where fluid is tested from amniotic sac to make sure baby is healthCVS = where blood is tested from chorionic villi to make sure baby is healthyUltrasound = sound waves to see what it looks likeAPGAR (appearance, pulse, grimace reflex, activity and respiration) = an after-birth test on ascale of 0-2 for five categories1. Appearance: we are looking for a healthy baby that is pink all over2. Pulse: should be over 120+3. Grimace: baby should cry4. Activity: want a baby who is moving5. Respiration: baby should be breathingRooting reflex: babies turn their head to the nipple if you stroke their cheekSucking reflex: babies suck on nippleBlink reflex: babies blink if you shine bright lightPupillary reflex: babies’ pupils dilatePalmar/grip reflex: babies hold to anything you place in their handsMoro reflex: babies throw their hands to catch stuffBabinski reflex: babies spread toes when bottom of foot is strokedStepping reflex: babies try to step forward if held above the floor___Teratogens = anything that puts newborn at risk when consumed by pregnant women. They aretime and dose dependent.Any alcohol is going to have some small effect on the baby. Lots of damage is done during the3-8 week period, after that not so much. 1 in 7 women report “risk drinking” during pregnancy:drinking more than 7 times a week.Three other risks1. Stress2. Low birth weight3. Age of motherMaternal stress can lead to premature births. This is not cause for concern on it’s own, butwhen paired with a low birth weight it can be scary, and they are at greater risk for stuff likesudden-infant death syndrome (which, while unknown in cause, occurs more when babies areasleep face-down)6 months: 10 inches, eyes formed, taste buds, can inhale and cry, can’t live7 months: “viable” but breathing is shallow7+ months to birth: living is possible, breathing is betterHow teratogens influence development1. Depends on the genotype2. Influence changes over development3. Affects specific aspects of developmentPregnant mothers should increase eating by 10-20%, and they should expect to gain 25-30pounds (⅓ baby, ⅓ fat, ⅓ more blood)Right before labor (a week or so) the baby starts dropping. We might see “false contractions,”which is the body essentially practicing for real labor. We might also see vaginal discharge,losing a few pounds, a dull backache, loose bowel movements or “nesting” (a sudden burst ofenergy before