208. Normal Pregnancy

Question 1

What changes occur during pregnancy to the reproductive tract: uterus, cervix/vagina, ovaries

Answer 1

Uterus: more blood flow as gestation progresses, more uterine weight, E-mediated hypertrophy, P-mediated relaxation (to allow for relaxation)

Cervix/Vagina: Chadwick sign: bluish tinge to cervix, hypertrophy/hyperplasia of cervical glands - eversion of proliferating columnar endocervical glands (beefy red columnar epithelium), increased mucosal thickness and loosening of c.t. in vagina

Ovaries: CL is heterogeneous and circumscribed by vessels, fx until W7; Decidual rxn: normal gray-white hemorrhagic nodules that can mimic malignancy; Theca-Luetin Cysts: assoc with high hCG, bilateral cystic ovaries, 25% with maternal virilization (ALL NORMAL)

Question 2

What are the effects of pregnancy on:

• CV
• Pulm
• GI
• Renal/GU

Answer 2

CV: diaphragm elevation (enlarged cardiac silhouette), high HR, CO (HR SV BV), decreases abruptly after delivery
BP: normal 1st trimester, low 2nd trimester (low SVR), normal 3rd trimester

Pulm: diaphragm elevation = low RV, low FVC
High minute ventilation due to high tidal volume = respiratory alkalosis (pH 7.40-7.45)

GI: high hCG causes N/V
P causes smooth muscle relaxation = GERD, constipation, low gallbladder motility (increase gallstone risk)
No change to gastric emptying time
High hepatic blood flow = high D-dimer, high Alk Phos, low albumin
Appendix location moves higher to RUQ as pregnancy progresses

Renal/GU: GFR increases 50% midpregnancy (Serum Cr normally decreases during pregnancy), renal plasma flow increases more than GFR, uterine displacement of ureters (R>L due to uterus rotation) causing hydronephrosis slight increase in kidney size

Question 3

What are the effects of pregnancy on:

• Heme
• Endo
• Metabolism

Answer 3

Heme: increase BV, plasma volume, RBC volume, relative anemia (higher plasma to RBC ratio), slight leukocytosis, coag/fibrinolysis augmented

Endo: most circulating hormones rise, P/E rise throughout
Fetal-placental interaction (need maternal chol., both produce androgens which dramatically increase maternal E)

Metabolism: increase BMR 10-20%
25-35lbs weight gain normal (max additional calories 300/day)
Carbs: hyperplasia of ins-secreting pancreatic B cells = increase ins secretion with progressive ins resistance = mild fasting hypoglycemia, post-prandial hyperglycemia
Protein: N balance increases with GA (more efficient use)
Fat: increase in lipids, apolipoproteins, more central fat storage

Question 4

Where does gas exchange occur in placenta?

Answer 4

Chorionic villi (bathed in maternal blood)

Question 5

What are the 3 CV Shunts in fetal physiology and how do they change at birth?

Answer 5

1. Ductus arteriosus: shunts blood from pulm trunk to aorta (less to lungs) due to high PVR in utero
2. Foramen ovale: from RA to LA
3. Ductus venosus: bypass fetal liver from umbilical vein

Birth: Alveolar expansion = increase capillary O2 = decrease PVR = decrease RA pressure and RV afterload = backflow of O2 blood into ductus arteriosus = alters PG production = local VC = closure of DA;
PFO closes as L side pressure > R side
Collapse of DV and umbilical veins

Question 6

What hormone detected in maternal blood is associated with time of birth? What does this hormone do?

Describe the control of the myometrium before and at labor?

What are the three stages of L&D?

Answer 6

CRH: synthesized in placenta

• stim maternal adrenals: increase DHEA-S: substrate for placenta to make E: induce myometrial contractility
• stim fetal pit/adrenals: rapid lung maturation (surfactant production), induce myometrial contractility

Pre-Labor: hyperpolarized/refractory due to Na/K ATPase (CRH, PGE open K channels and maintain relaxations - stop uterine contractions)
Labor: PG-F and Oxytocin bind = open ligand gated Ca channel = open V gated Ca channel = high intracell Ca = myosin light chain kinase = contraction

1: labor to full cervical dilation (latent - slow unpredictable; active - faster rate of dilation, starts 4-6cm, around 6hrs), repeat pregnancy has more defined switch point from latent to active
2: from full cervical dilation = delivery of fetus (expulsive efforts)
3. from delivery of neonate to delivery of placenta