Fastest growth in 1st half of pregnant, before fetal growth spurt
What does the placenta do?
Exchange of nutrients, respiratory gases, metabolic waste, protection of fetus, source of hormones
How does the placenta transfer nutrients to the fetus?
Umbilical cord attaches to the placenta, arteries divide into vessels which branch into placental villi
What is amniotic fluid?
Shock absorber and prevents dessication of fetus, provides room for fetal movements and assists in body temperature regulation
What are cytrophoblasts?
Cells from placenta that connect mother and fetus, evolve into tumor-like cells and establish blood flow to the fetus
How are the fetal and maternal placenta attached?
Fetal and maternal placenta anchored together by cytotrophoblastic shell and anchoring villi
Large area for exchange of materials
How does deoxygenated blood leave the fetus?
Deoxygenated blood leaves the fetus and passes through the umbilical artery to the placenta. Arteries divide into radically disposed vessels which branch into the chorionic plate (fetal surface of placenta) before entering the villi
What is the major functioning unit of the placenta?
What causes IUGR infants?
IUGR infants have microscopically less branching of villi
What are the functions of the placenta?
How does the placenta contribute to metabolism?
Synthesizes compounds used by the fetus (glycogen, lactate, cholesterol)
50% of oxygen and 6% of glucose of maternal blood is used
What is the placental membrane?
A barrier because a few compounds (large MW) are unable to cross
Same mechanisms typically found in the small intestine (active transport, facilitated diffusion, and passive diffusion)
How do fatty acids cross the placenta?
Partly via diffusion but also involves carrier mediated transfer (enhancement of PUFA transfer)
Generally poor transfer of fat soluble vitamins
Which compounds use facilitated diffusion to cross the placenta?
Sugars, long chain PUFA
Which compounds use active transport to cross the placenta?
Amino acids, carions, water soluble vitamins
Which compounds use solvent drag to cross the placenta?
Water and solutes such as electrolytes due to osmotic pressure
How is glycation a mechanism of teratogenesis prevented?
Use of glucose transporters protects the fetus from high levels of glucose
How is the difference between fetal growth rate and placental growth rate in the last 10 weeks combated?
To compensate for the increased fetal needs, the placental blood flow increases as the pregnancy progresses
This partially compensates for the lower rate of placental growth, which is a limiting factor to transfer enough nutrients for the fetal needs
Why is there a deceleration in the rate of fetal growth in the last 4 weeks of gestation?
There is a progressive decline in the quantity of nutrients transferred per unit of fetal body mass per unit time
If the placenta fails, what is the cause?
If the placenta fails, it is often due to the related failure of the uteroplacental blood vessels to deliver increased uterine blood low
What can cause a reduction in the maternal placental circulation?
A variety of conditions which decrease uterine blood flow such as: sever hypertension, renal disease, or placental infarction
How can essential fatty acids effect the placenta?
Essential fatty acid deficiencies can cause defects in placental integrity and function
Low concentrations of linoleic acid, arachadonic acid, and DHA have been associated with what?
Short gestation and small head circumference
What is biomagnification in relation to fetuses?
Selective transfer of 20-22 carbon essential fatty acids to the fetal brain
How much energy is devoted to brain development in fetus?
How much of the brain matter is lipids?
What is the function of human chorionic gonadotropin?
Maintains the corpus luteum which secretes estrogen and progesterone, which are necessary to support the first trimester of pregnancy
Where does human chorionic gonadoptropin come from?
Secreted by blastocyst on day 7
After implantation, placenta produces huge amounts, which peak between the 10th and 11th week and then is maintained at a low level throughout pregnancy
What is human placental lactogen?
Produced by placenta in late gestation
Influences fat and CHO metabolism, may be responsible for insulin resistance and CHO intolerance observed in pregnancy
Breaks down maternal fats for fuel
What are some functions of the placenta?
Protection agains Xenobiotics
Where is progesterone produced?
Produced by the corpus luteum until 10 weeks of gestation, then the placenta takes over
What does progesterone do?
Inhibits secretion of pituitary gonadotrophins (LH and FSH) to prevent ovulation
Supports the endometrium
Suppresses contractility in uterine smooth muscle
When are estrogen levels maximal?
Toward the end of gestation
What does estrogen do?
Stimulates myometrium growth, antagonizes myometrial-suppression by progesterone, stimulates mammary gland development
What are some physiological adjustments during pregnancy?
Increased blood volume
Altered stomach, cardiac, renal and pulmonary functions
Altered plasma lipid profiles
Altered appetite and thirst
Altered digestion and assimilation of food
When do most of the physiological changes occur in pregnancy?
1st half of gestation
How does renal function change during pregnancy?
Increased glomerular filtration rate and decreased tubular re-absorption capacity--> increased excretion of fetal waste products but ALSO increased renal loss of glucose, folate, iodine and amino acids
Why does stomach function decrease during pregnancy?
Decreased histamine and pepsin
Why is there an increased risk of heartburn during pregnancy?
Relaxed cardiac sphincter
Why is there an increased risk of constipation during pregnancy?
Decreased GI motility and insufficient fluids
Why is there increased ventilation during pregnancy?
Increased oxygen demands
What causes impaired hepatic gluconeogenesis during pregnancy?
Decreased muscle breakdown and increased placental uptake of alanine --> decreased alainine availability --> impaired hepatic gluconeogenesis
What is the anabolic phase?
Extra CHO stored as glycogen or converted to fat
Fats rapidly synthesize into TGs (conserve fat stores)
Increase in maternal protein synthesis (RBC and placenta)
What is the catabolic phase?
Fat mobilized to conserve glucose for fetus
Increased ketones. increased blood cholesterol
Insulin action blunted after meals by estrogen, progesterone, placental lactogen
Glucose increased for greater uptake by placenta which does not rely on insulin
How much of your body weight should be fat?
How much weight should be gained during pregnancy?
28-40 pounds (12.5-18kg)
What is the pattern of weight gain during pregnancy?
3-4 lbs for 1st 10 weeks
1lb/week for rest of pregnancy
What happens if the mother gains too much weight during pregnancy?
Indicates likely presence of excessive edema and risk for preeclampsia
Increased risk of separation of placenta, stillbirth, decreased blood flow to placenta and low birth weight
What can be caused by insufficient blood volume expansion?
Correlated with still births, LBW and spontaneous abortions
Edema is commonly present
What is obligatory weight gain during pregnancy?
fetus, placenta, enlarged uterine and breast tissue, expanded blood volume