Conception and Fetal Development

last menstrual period (LMP)

when reliable, most accurate estimator of gestational age

lunar months

time period clinicians measure pregnancy gestation in

10

number of lunar months of a full term pregnancy, equal to 40 weeks

CD14

lunar months assumes ovulation and conception of this of a 28-day cycle

preembryonic stage

this stage includes: fertilization and implantation + placental development

fertilization

defined as sperm and ovum uniting to form a zygote

ova

this half of fertilization is fertile for 12-72 hours

sperm

this half of fertilization is fertile for 72 hours

fertilization

point at which the sex of the zygote is determined

day 6-7

day at which the blastocyst attaches to the uterine wall

trophoblast

these cells develop outside of the blastocyst (which become inner cells)

day 11-12

day at which implantation of the embryo occurs and the placenta begins to form

placenta

this temporary organ performs many functions, including: hormone production (hCG, progesterone, estrogens, etc.) and metabolic functions (respiration, nutrition, etc.)

cotyledons

the placenta is made up of 15-20 smaller segments called

maternal

this portion of the placenta is red and flesh-like

chorion

the fetal membrane of the maternal portion of the placenta

decidua

after implantation, the endometrium is called

fetal

this portion of the placenta is shiny and gray

amnion

the fetal portion of the placenta is covered by this

fetal membranes

consists of the chorion and the amnion

chorion

fetal membrane located on the outside, toward the uterus

trophoblast

the chorion develops from this part of the early embryo

chorionic vili

the chorion contains these on the surface - “fingerlike” projections that extend into the endometrium

umbilical blood vessels

the chorion contains these, helping to provide all metabolic functions to the fetus

amnion

this inner cell membrane develops from the interior cells of the blastocyst

amnion

this fetal membrane portion becomes the covering of the umbilical cord

amnion

covers chorion of the fetal surface of the placenta

chorionic vili

projections that obtain O2 and nutrients from maternal blood, and dispose of CO2 and waste products into maternal blood

diffusion

chorionic vili and maternal blood vessels CANNOT communciate directly, so fetal needs are met via this process

wharton’s jelly

specialized connective tissue of the umbilical cord covering the 2 arteries and 1 vein

whartons jelly

prevents compression of the umbilical cord in utero

umbilical cord

this structure provides the circulatory pathway from the chorionic vili to embryo

2 arteries

these umbilical vessels transport WASTE from fetus to the mother

small

the arteries of the umbilical cord are this in relation to the vein

1 vein

this umbilical vessel transports O2 and nutrients from mother to fetus

large

the vein of the umbilical cord is this in relation to the 2 arteries

amniotic fluid

this fluid first develops from diffusion from maternal blood

increases

over the course of pregnancy, the amount of amniotic fluid…

urination

the way by which the fetus increases amniotic fluid volume

amniotic fluid

this vital fluid’s functions include: maintaining temperature, acting as waste repository, protects fetus from trauma, and allows freedom of movement

oligohydramnios

condition of <400mL of amniotic fluid

polyhydramnios

condition of >2000mL of amniotic fluid

embryonic period

period of fetal development that lasts from day 15 - 8 weeks post conception

crown rump length (CRL)

during the embryoic period, this is approx 3cm

embryonic period

the most critical time in the development of organ systems and main external features

8 weeks

by this time period post conception, all organ systems and external structures are present but not functionally complete

teratogen

agent that acts directly on the developing fetus, causing abnormal embryonic or fetal development

early embryonic period

the point in time when a fetus is most vulnerable to teratogens

3 weeks

teratogens can cause heart, limb, eye, etc. malformations as early as…

valproic acid

teratogen that causes neural tube defects

lithium

teratogen that causes heart abnormalities

torch

acronym for microorganisms associated with known congenital diseases

toxoplasmosis gondii

“t” in the torch acronym

other

“o” in the torch acronym, which includes: listeria, treponema pallidum, varicella zoster virus, HIV, enteroviruses, and parovirus B19

rubella

“r” in the torch acronym

cytomegalovirus

“c” in the torch acronym

herpes simplex virus-1 and -2

“h” in the torch acronym

toxoplasmosis gondii

teratogen pathogen that invades tissues and damages the fetal brain

rubella

teratogen pathogen, a viral infection with incubation period of 2-3 weeks and increased risk for miscarriage or stillbirth

congenital rubella syndrome

rubella infection that can occur if infected within the first trimester

autism

rubella can cause this developmental abnormality

deafness, cataracts, and heart defects

3 most common defects of rubella

MMR

pregnant people should NOT get this vaccine, and most wait 1 month post vaccine to get pregnant

cytomegalovirus

teratogen pathogen that is the most common perinetal infectious agent (1% of live births)

CMV

teratogen pathogen passed through close contact and bodily fluids

congenital CMV

teratogen pathogen that occurs in 1:200 babies and has a 3-105 infant mortality rate in symptomatic infants

hearing loss

major defect of congenital CMV infants - the leading cause of this in US children

neonatal HSV

teratogen pathogen that occurs in 1 in 2000 live births in the US, 85% intrapartum

antiviral therapy

pregnant patients with an active HSV infection are given this beginning at week 36

acyclovir 400mg or valacyclovir 500mg

antiviral therapy for pregnant active genital HSV patients

congenital syphillis

major teratogen pathogen that is transmitted via placenta during pregnancy or close contact with maternal lesions post-birth, RATES INCREASING

syphilis risk factors

these account for increasing rates of this in US live births, includes: late/no prenatal care/PNC, inadequate maternal screening, and maternal HIV infection

40%

probability of miscarriage, stillbirth, or death in an untreated maternal syphilis infection

congenital syphilis

symptoms of this in infants include: Hepatosplenomegaly, copious snuffles, musculocutaneous lesions, etc.

congenital syphilis

late manifestations of this in children born with this condition include CNS, bone and joint, teeth, eye, and skin abnormalities

fetal stage

period of gestation from 9 weeks gestation up until birth

teratogens

in the fetal stage, the baby is less vulnerable to these EXCEPT THOSE AFFECTING THE CNS

viability

ability of the fetus to survive outside the uterus, ~22 weeks

cardiovascular system

first system of fetus to function - heart complete by end of embryonic period

2 arteries

vessels that deliver deoxygenated blood to the placenta (waste products)

1 vein

vessel that delivers oxygenated blood to the fetus

ducts venosus

fetal circulation shunt that connects the umbilical vein to the inferior vena cava

foramen ovale

fetal circulation shunt between the left and right atrium, bypassing pulmonary system

ductus arteriosus

fetal circulation shunt that connects the aortic arch and pulmonary artery

pulmonary surfactants

marker used to determine degree of fetal lung maturity and ability of the lungs to function after birth

lecithin

most critical surfactant required for postnatal lung expansion

sphingomyelin

surfactant that remains constant in amount

l/s ratio

ratio that should be 2:1 to be considered a mature resp. system, around 35 weeks

respiratory distress syndrome

syndrome present at birth due to d/t insufficient surfactant and alveoli collapse with no gas exchange

hematopoiesis

process of RBC formation that begins in the liver at about 6 weeks

bone marrow

takes of blood cells production by week 24

antigenic factors

blood type marker present after the 6th week

isoimmunization

immune response when different blood types mix

bilirubin

substance metabolized by the liver that made when old RBCs are broken down - metabolic pathways for disposal are not at adults levels even for newborn

placenta

main route for bilirubin excretion

GI system

changes from a straight line/tube to a C shape around week 4

foregut

forms the esophagus, stomach, and duodenum around week 5/6

midgut

becomes the small intestine and part of the large intestine

hind gut

turns into the colon and rectum

meconium

as fetus nears full term, waste products collect in GI system as this