chapter 3 - pregnancy and prenatal dev

cephalocaudal principle

“head to tail”, D that starts at head and then works from top to bottom, happens at same time as proximodistal principle

proximodistal principle

“near to far”, D starts from center and works outward, happens at same time as cephalocaudal principle

germinal stage

conception-2 weeks, when one cell divides over and over, implantation happens at end of this stage, by 2 weeks a placenta, umbilical cord, and fluid have formed, only 10-20% of fertilized eggs implant

embryonic stage

2-8 weeks, key time where major organs and body system develops, embryo sensitive to environment, 80% miscarriages happen during first 3 months due to chromosomal abnormalities, estimate ¼ known pregnancies are miscarried

fetal stage

8-40 weeks, “finishing touches” D and baby grows 20x in length

fetal hearing

babies can respond to sound and vibration

fetal “learning”

babies like higher pitched voices and can distinguish mom’s voice (most soothing) as well as dad’s, can even differentiate language

nutrition and prenatal environment

should expect to gain 25-30lbs, mother’s diet matters, ie. need enough folic acid

teratogens and prenatal environment

any E factor that interferes with normal D and can cause a birth defect

teratogens: medical drugs

no meds should be taken unless considered essential

teratogens: alcohol

prenatal exposure is leading cause of preventable birth defects and intellectual disability, FAS (fetal alcohol syndrome) babies have slight physical differences and longterm L/intellectual disability

teratogens: marijuana

most commonly used illegal drug during pregnancy and rates of use have increased over last 10 years, connected to prematurity and low birth rates, long term higher risk of low attention span and L disorders

teratogens: nicotine

most important factor for low birth weight in developed countries, related to increased infant death rate, contributes to SIDS (baby death), 6.5% of pregnancies women smoke

teratogens: cocaine/crack

associated with being born early, abnormal reflexes, low birth weight, and longterm B and habituation problems

teratogens: caffiene

slightly increased rates of miscarriage, still birth, and low birth weight but studies have mixed reviews

maternal factors: illness

timing matters for serious defects, hiv/aids can be transmitted from mom to baby prenatally but chances can be decreased if meds are taken

maternal factors: rh factor

is the ± in blood (+ has it), if mom is - and baby is + then the mom’s immune system can attack baby and lead to serious defects, chances increase with each pregnancy

maternal factors: maternal age

moms over age 35 are more likely to experience complications, ie. increased blood pressure, teen moms more likely to have babies with low body weight or premie babies

maternal factors: paternal factors

father’s diet, age, exposure to substances, etc. are connected to birth defects (sperm quality)

ultrasound

high frequency soundwaves to see image of the uterus/fetus, considered no risk, only ~60% moms do this

maternal blood tests

take mom’s blood and can measure alphafeto protein levels which can identify 99% down syndrome cases and also neural tube defects, although 50% down syndrome yes’s are false positives

prenatal cell-free dna

tests mom’s dna after 12th week of pregnancy to get baby’s dna, can identify down syndrome, trisomy 13, and 18, not super specific especially with twins, triplets, etc., can pick up on gender

amniocentesis

ultrasound guides needle but then a hollow needle goes through the abdomen to obtain amniotic fluid to get baby’s skin cells in order to find chromosomal abnormalities, only 2% moms do this, done between 15th-20th week, can trigger miscarriage in 1-3%, follow up for pcf dna

chorionic villus sampling

needle through belly or catheter, taking a tissue sample from membrane around embryo to produce a karyotype, 10-12th week of pregnancy, 3-5% miscarriage rate

umbilical cord blood sampling

same as amniocentesis but directly draws baby’s blood, not done often and only if there’s a concern with infection for example

preimplantation genetic diagnosis

only done with IV fertilization, taking karyotype from the blastocyst’s cells and only implanting healthy cells to “screen out” disorders