Pregnancy - Montemayor Flashcards
How is pregnancy duration determined?
Date of last mestrual period (LMP)
What is the mean duration of pregnancy?
40 weeks total (gestational age)
Or
38 weeks from ovulation - (embryonic/fetal age)
When do HCG levels begin to rise after ovulation of a fertilized egg?
8 Days
What secretes HCG?
The trophoblast
What are the four major hormones of pregnancy?
- HCG
- Progesterone
- Estrogens
- Human Placental LActogen (hPl)/Human chorionic omatomammotropin (hCs)
What are the three types of estrogens to be aware of?
Estrodiol
Estrone
Estriol
Identify which line corresponds with what hormone.
In the first trimester, hCG rescues the corpus luteum to stimulate luteal estrogen and progesterone production. What takes over hormone synthesis from the corpus luteum?
The placenta
What subunit of hCG is detected by pregnancy tests?
Beta subunit. (beta-hCG)
What is responsible for morning sickness?
hCG
When does hCG peak?
~10 weeks of gestation.
What hormones is the structure of hCG similar to? Which is it most similar to?
LH, FSH, TSH
Most similar to LH
hCG binds to what receptor with high affinity?
LH receptors
What is the primary action of hCG?
Stimulates LH receptors on corpus luteum…
- Prevents luteolysis
- Maintains high luteal-derived progesterone production before the placenta takes over (1st 10 wks.)
What are the other actions of hCG?
–Weakly binds TSH receptors
•Transient gestational hyperthyroidism
–Stimulates fetal Leydig cells –> Testosterone
–Stimulates fetal adrenal cortex
When does the luteal-placental shift take place?
~8-10 weeks
What is the function of progesterone with regard to pregnancy?
•Absolutely required to maintain a pregnant uterus
–Quiescent myometrium
How is progesterone production an indicator of fetal health?
It isn’t, progesterone production is independent of fetus
High levels of progesterone production continues with the availability of?
•CYP11A1, and 3β-hydroxysteroid dehydrogenase (3β-HSD), and **maternal cholesterol **
What are the major actions of progesterone in pregnancy?
–↓ uterine motility/contractions
–↑secretory activity necessary for nouishment, growth, and implantation of the embryo
–↑ fat deposition early in pregnancy
•Stimulates appetite, diverts energy stores from sugar to fat
The placenta takes of luteal-production of estrogens, what does it need from the fetal adrenal gland?
Needs 19-carbon androgen (DHEA-S)
What is the feto-placental unit responsible for the production of?
–Estradiol-17β
–Estrone
–Estriol (major estrogen of pregnancy)
Can you use estrogen as an indicator of fetal health?
Yes, since its production depends on a healthy fetus
We discussed seven effects of estrogen in pregnancy, list as many as you can.
- –↑ Uteroplacental blood flow
- –↑ Uterine smooth muscle hypertrophy (mitogenic effect)
- –↑ LDL receptor expression on syncytiotrophoblasts
- –↑ Prostaglandins
- –↑ Oxytocin receptors
- –↑ Mammary gland growth
- –↑ Prolactin secretion (maternal pituitary)
The estrogen:progesterone ratio shifts late in pregnancy, why?
To prepare for parturition
What does the drop in estrogens and progesterone after parturition allow for?
•PRL action on the breast and lactation
Human placental lactogen (hPL) is also known as?
•Human chorionic somatomammotropin (hCS)
What produces hPL/hCS?
syncytiotrophoblasts
What are the levels of hPL proportional to?
Placental growth
What is the main action of hPL?
•↑ glucose availability for the fetus
–Inhibits maternal glucose uptake
–Lypolytic action –> shift maternal energy use to FFAs
What else does hPL do besides its antagonism of insulin activity?
•Simulates mammary gland development
What are some things that can cross the placental barrier? (mother to fetus)
- O2
- water
- electrolytes
- carbs, lipids, a.a., vitamins
- hormones (some)
- antibodies
- drugs (some)
- Viruses (most)
Syncytiotrophoblasts produce what classes of hormones?
Steroid and peptide hormones
Name five functions of the placenta
- Maintain pregnant state of the uterus
- Stimulate lobuloalveolar growth and function of maternal breasts
- Adapt aspects of maternal metabolism and physiology to support fetal growth
- Regulate aspects of fetal development
- Regulate the timing and progression of parturition
Identify the hormones shown on the graph.
What are two major limitations of the placenta?
- Cannot make adequate cholesterol
- Lacks enzymes required for complete biosynthetic pathway for estrone, estradiol, and estriol production.
Identify the blocked out items
What are the changes to the pituitary during pregnancy?
- ↑ Pituitary size x 2
- ↑ Prolactin (PRL)
- ↓ LH and FSH production
- ADH secretion augmented
What can happen due to the increased pituitary size in pregnancy?
–If compressed against optic chiasm, enlarged pituitary can cause dizziness and vision problems
–Can be susceptible to vascular insult and necrosis – Sheehan’s syndrome
What does the increased prolactin during pregnancy lead to?
–Estrogen promotes PRL release from anterior pituitary
–Lactotroph hypertrophy and hyperplasia
What causes the decreased LH and FSH production during pregnancy?
–Negative feedback inhibition of estrogens + progesterone
In what way is ADH secretion augmented during pregnancy?
–Threshold altered by progesterone action
–ADH released at lower osmolality (lower “set point”)
What happens to the thyroid during pregnancy?
•↑ Thyroid size
•hCG weakly binds TSH receptors
–Transient gestational hyperthyroidism
•↑ Total T4 and Total T3 (2x)
–Estrogen promotes increased liver production of thyroxine-binding globulin (TBG)
–No change in Free T4 and Free T3
What adrenal changes occur during pregnancy?
- ↑ Cortisol
- ↑ Aldosterone (~ 8-10 x)
What does placental 11β-dehydrogenase type 2 do?
Inactivates cortisol to protect the fetus
How is aldosterone upregulated in pregnancy? Do we get hypernatremia, hypokalemia, hypertension? What blunts the action of aldosterone?
–Estrogens stimulate ↑ liver production of angiotensinogen and renal renin production
•↑ ANG II and Aldosterone
–Does not result in hypernatremia, hypokalemia, or hypertension
–Progesterone blunts aldosterone action (competes for mineralocorticoid receptors)