Week 5 Prenatal Development Part 1 note outlines True or false Playing music near a pregnant woman s abdomen can stimulate advanced cognitive development in the baby False Excessive drinking while pregnant can cause Down syndrome False An occasional beer or glass of wine during pregnancy is safe as long as it s limited to that False Women who smoke pot while pregnant have children more likely to become addicted to marijuana as adults True Premature infants often have developmental problems and lag behind their peers False Modern American couples mostly share household and child care responsibilities False Conception the moment at which a female becomes pregnant Egg aka Ovum the female gamete aka sex cell Sperm the male gamete aka sex cell Fertilization the union of the ovum and sperm Stages of Prenatal Development TIME PERIODS 266 280 days 38 40 weeks 9 months Divided into 3 equal trimesters 0 3 4 6 7 9 mos PHYSICAL PERIODS not the same as time periods Zygote first 2 weeks after fertilization germinal period Embryo 3rd through 8th weeks of gestation Fetus 9th week until birth The developing organism The pluripotent zygote develops into an embryo with semi specialized cell layers then into the complex multisystem fetus which has distinctly specialized cell types Four major developmental processes from zygote to embryo to fetus Cell division mitosis the creation of new cells Cell migration the movement of cells from their point of origin to their ultimate location where they become functionally specialized Cell differentiation transforms unspecialized stem cells into roughly 350 different types of cells with specific functions Apoptosis programmed beneficial cell death of selected cells Removal of unneeded neurons as neural circuits in the brain are wired Removal of unneeded tissue as body is formed and refined Stage 1 The Zygote 0 2 weeks 2 week period starting with conception Zygote travels through the fallopian tube to the uterus Zygote stage ends with implantation to uterine wall 50 do not successfully implant Stage 1 The Zygote 0 2 weeks Zygote stage rapid mitosis and initial cell migration into 2 layers outer layer will become the placenta inner cells layer become the developing embryo Stage 1 Ectopic pregnancies Instead of implanting on the uterine wall the blastocyst attaches to a different area of the reproductive system Usually fallopian tube Ectopic pregnancies cannot be carried to term and cells must be removed surgically Stage 2 The Embryo Embryonic period Prenatal period from 2 weeks through 8 weeks Cell differentiation and migration intensify forming 3 distinct layers Endoderm will become digestive and respiratory systems Mesoderm will become bones muscles circulatory excretory and reproductive systems Ectoderm will become nervous system and brain sensory organs and skin hair and nails Neural tube a U shaped groove formed from eventually becomes the brain and spinal cord Stage 2 The Embryo the ectoderm While they are being formed the embryo parts are especially vulnerable to environmental events Many serious environmentally induced birth defects originate during the embryonic period Face Development Stage 3 The Fetus During fetal period 9 weeks birth Fetus is about the size of your thumbnail at first Rapid CNS and muscular development cell migration and differentiation All organs complete their differentiation and begin working 12 weeks sex organs start to emerge 14 weeks 3 months chance of a miscarriage is 1 for most women 16 weeks 4 months heart and blood vessels are fully formed fingers and toes have fingerprints About the length of a car key Weighs about 3 5 ounces Fetus at 20 Weeks halfway there weighs about 10 ounces About as long as an ink pen can suck a thumb yawn stretch and make faces Mom can usually feel movement quickening Ultrasound performed to confirm placenta is healthy and fetus is growing properly Fetus at 24 Weeks weighs about 20 oz doubled in 4 weeks Inner ear fully developed responds to sounds by moving or increasing its pulse rate Eyes can open and close Nearing viable zone More than 12 oz At least 23 weeks Fetus at 28 Weeks weighs about 2 pounds 40 oz changes position frequently good chance of survival if born prematurely now Time for birthing classes to prepare for labor and parenting the newborn Fetus at 36 Weeks about 18 5 inches long close to 6 pounds lungs are nearly fully developed Brain is only about 2 3rds as big as 39 40 weeks head is usually positioned down into the pelvis by now Fetus at 39 weeks full term the average American full term baby weighs 7 pounds and is about 20 inches long Size of a bag of flour loaf of bread Full term healthy newborn 39 40 weeks 7 lbs Organs are complete baby is viable Often need to build fat Focus is on eating sleeping and growing mentally and physically Prenatal Development Part 2 What if something goes wrong But what if things go wrong Miscarriage is when a fetus dies in the uterus before 20 weeks of pregnancy 10 15 of known pregnancies 95 99 occur in the first trimester first 12 weeks Most are caused by problems with chromosomes or genes Physical recovery can take a few weeks It may take longer to recover emotionally Most women who miscarry go on to have a healthy pregnancy later Premature and low birth weight Premature birth 38 weeks or less Medical ethics advise not resuscitating babies 23 weeks gestation because it is not in the child s best interests respiratory distress syndrome from underdeveloped lungs hypoxia Additional underdeveloped organs blindness deafness heart problems Neurological underdevelopment brain bleeds cerebral palsy System deficits such as hypoglycemia body temp disregulation Low birth weight LBW 5 5 lbs or less MDs observe that 12oz rarely survive Most preemies are also LBW Premature and low birth weight Full term babies can also be LBW Called small for date or small for gestational age Weak thin pale loose dry skin poor feeding temp disregulation hypoglycemia hypoxia heart problems Increased infant mortality neurological defects behavioral problems obesity diabetes heart disease Common predictors In mom malnutrition poor or no prenatal care drug or alcohol use serious infections and mom OR partner smoking In utero inadequate prenatal nutrients inadequate oxygen flow umbilical cord problems Pre eclampsia toxemia when mom s blood pressure suddenly spikes to life threatening levels for which the ONLY solution is early delivery Chromosomal abnormalities in the fetus Smallest