Pregnancy and Lactation - Dr. Nicholas J.D. Wright, PhD

What happens prior to ovulation as a results of the LH surge with regard to fertilization?

Egg start to complete meiosis (first polar body) and is released into the abdominal cavity

Where does the egg go after it is released into the abdominal cavity?

Fallopian tubes (know this is where fertilization happens)

Eggs/ovum that are released (with many granulsoa cells) form what structure?

Corona radiate

What mechanism allows the egg to move into the fallopian tubes?

estrogen-activated cilia

What mechanisms aids the sperm to ascend into fallopian tubes?

prostaglandin and oxytocin induced contractions + reversed cilia

When is meiosis completed to form the second polar body?

After penetration of the sperm into the ovum (must pentrate walls of radiate to fertilize)

How long after fertilization does the egg implant, and what happens at this point?

~1-3 (5-6 days after ovulation)

Placenta starts to develop

What cells form the placenta?

Trophoblast cells of blastocysts

What are trophoblast cells?

proteolytic enzymes that digest the endometrium

How is the endometrium maintained following fertilization?

Progesterone secreted by corpus luteum secondary to hCG

What is the main mechanism of getting necessities across the placenta when cell mass is still small?

Diffusion

How do trophoblastic cells grow/develop?

as chains/cords

At what point in gestation is a heartbeat required to sustain the baby?

~16 days after fertilization

How is circulation different in a fetus?

Circulation is reversed -> arteries carry deoxygenated blood to placenta, veins carry oxygenated blood

Fetal Hb has a higher or lower affinity for O2?

Higher - facilitates transfer to get more Hb/unit volume

Exchange area of placenta is small or large to allow for simple/facilitated diffusion?

Small

Acidic environment produces the Bohr effect that shifts the Hb saturation curve what way? What does this mean?

Right side, more O2 release

Fetal is blood is slightly more alkaline or acidic to produce a left-shift in the O2 sat curve left to further enhance oxygen delivery to fetus?

alkaline (mother more acidic, fetal more alkaline?)

What hormones does the placenta produce?

hCG, hCS, estrogens, progesterone

What maintains the corpus luteum for 2-4 while fetus develop in early stages?

hCG

What produces hCG in the placenta?

Trophoblast cells

hCG production during pregnancy substitutes for what hormone?

LH

At what point in gestation is the placenta fully mature and begins to secrete sex steroids?

12 weeks

Estrogen increases throughout pregnancy serve what purpose?

Growth of uterus

Development of breasts and external genitalia

The anterior pituitary enlarges during pregnancy, which increases secretion of what hormones to meet metabolic demands of the fetus?

TSH

ACTH

Prolactin

The thyroid enlarges during pregnancy likely in response to what hormones?

hCG

hCT

When does the parathyroid enlarges during pregnancy?

If the mother has low plasma calcium levels

(more PTH after birth for calcium-rich milk production)

What changes occur to sex hormones and gonadotropins during pregnancy?

Increased sex steroids

Low gonadoptropins

What hormone increases during pregnancy and tends to cause water retention and pregnancy-induced HTN?

Aldosterone

What hormone released by the corpus luteum via hCG that works to relax symphysis ligaments, ultimately increasing diameter of birth canal and soften cervix

Relaxin

What is the average weight gain in a single pregnancy?

~24 lbs

Where is oxytocin produced and what causes its production?

Anterior pituitary, stimulated by physical stimulation of cervix

The uterine muscle is stimulated BOTH directly and indirectly by what mechanism?

Stretching (CNS reflexes)

What is birth induced by?

Rupturing membranes that allow for greater stretching of the cervix

What contractions are observed through birth? Are they weak or strong?

Braxton Hicks contractions

Slow, weak contractions

What happens to contractions as the mother gets closer to birth?

Frequency and intensity increases

Birth is what type of feedback?

Positive

What levels decrease immediately after birth and what purpose does this serve?

Estrogen and progesterone decrease

Allows prolactin to complete breast preparation for milk production

what role does prolactin play in breast feeding?

Stimulates milk production for next feed

What role does oxytocin play in breast feeding?

causes milk contraction and ejection

T/F: Mothers milk contains useful antibodies and WBCs

True

Normal cycling typically resumes when?

Once nursing has ceased