Partuition Flashcards
Four phases cervix goes through in pregnancy
Softening occurs during the majority of pregnancy,
Ripening occurs 1-2 weeks before labor,
Dilation occurs during labor
Postpartum repair occurs after delivery.
Cervical dilation is likely a result of t
he mechanical force from contractions and fetal head descent, and changes in cervical composition leading to increased compliance.
In early pregnancy, uterine growth is secondary to _________; myometrial cell hypertrophy leads to uterine growth from mid gestation onward. Uterine fibrous and connective tissue, blood vessels and lymphatics also increase during pregnancy.
myometrial cell proliferation
Myometrial cells proliferate in early pregnancy
- Myometrial cells hypertrophy in____ half of pregnancy
- ______between myometrial cells increase during pregnancy
- Major increase in the blood supply to the uterus
later
Gap junctions
*17% gravid and 2% non-preggers
• Myometrium is comprised of smooth muscle: Contractility is dependent on
spontaneous action potentials increasing intracellular calcium leading to activation of ATPase through a phosphorylation pathway.
Myometrial cells contract in synchrony during labor leading to frequent, forceful, and longer contractions. Synchrony is achieved by
the passage of currents through gap junctions made of proteins called connexons. These increase in size and abundance during pregnancy.
Myometrial Cells can spontaneously contract
- Spontaneous action potential
- No hormonal input is needed
- No nervous input is needed
How are uterie contractions generated?
• Myometrial action potential–> Increase in intracellular
calcium–> Calcium binds calmodulin–>Myosin light chain kinase
activated–> Myosin is phosphorylated –>ATP is hydrolyzed
Myosin undergoes structural change–> Myosin forms a crossbridge with actin leading to contraction
Transition from the quiescence phase to labor phase involves a shift from_____ dominance to____ dominance
progesterone –> estrogen
Inhibits intracellular Ca entry
Inhibits release from sarcoplasmic reticulum
Membrane hyperpolarization via potassium channels
Inhibits expression of CAP genes
Levels are constant before and during labor, tissue level may vary
Progesterone
Increases gap junctions btwn myometrial cells allowing for contraction synchrony between cells
Increases oxytocin receptor and prostaglandin receptor expression in myometrium.
Estrogen
- Initiate excitation
- Increase frequency and amplitude of contractions
see more of these going into labor
• Uterine stretch and Estrogen upregulate contraction-associated proteins (CAP) in the myometrium
Gap Junction protein connexin-43
Oxytocin receptor
Corticotropin-releasing hormone receptor
Cyclo-oxygenase (COX)-2 enzyme
all upregulated in labor
What type of contraction do we see during labor
G protein coupled receptor –> Activates phospholipase C –>Stimulates release of calcium from intracellular stores–> Myosin light chain kinase activation
_____synthesized by hypothalamus, stored in the posterior pituitary, increases prostaglandin and estrogen level
Oxytocin
Possible triggers for labor
- Fetal adrenal gland plays an important role
- Contributes to the idea of fetal signal
- Increased maternal estrogens
- Increased prostaglandins
- Increase in CAP
Once the baby has fnx adrenal gland, increases production of ______ that can get converted into estriol to upregulate CAPS as the fetal/maternal membrane
baby makes DHEAS
The baby can make _____ which will increase placental oxytocin, prostaglandinsand placental CRH during induciton of labor which goes to mom to further stimulate labor
cortisol
Latent phase: contraction with slow cervical dilation
Active phase: contractions with fast cervical dilation
First stage of labor
Complete dilation until delivery of fetus
Post delivery of fetus to delivery of placenta
SEcond phase
Third phase
Lasts one hour after delivery of placenta Constant myometrial contraction that limits blood loss
Fourth stage
delivery between 20 weeks gestation and 37 weeks gestation
- Contraction mechanism is the same
- What leads to the contractions is likely different
leading cause of infant mortality and long term neurological disabilities
Preterm Labor
4 factors involved in preterm labor
Uterine distension
Maternal fetal stress
Premature rupture of membranes
infection
How can infetion lead to premature labor?
• Toxins produced by bacteria stimulate to cytokine production leading to prostaglandin release
How does uterine distension lead to preterm labor?
- CAP expression
- CRH and Estrogen increase
- Oxytocin release
- Uterine activation
How does maternal-fetal stress lead to premature labor
• Premature rise in cortisol and estrogens can induce labor phenotype and stimulate fetal adrenal c19 hormones
Identifiable preterm labor risk factors
infection, periodontal disease, smoking, genetics, cervical shortening, decreased uterine space, low pregnancy weight
Used to Tx preterm labor
magnesium, Ca+ channel blockers, Prostaglandin synthesis inhibitors, B-2 adrenertic receptor agonist
(via inhibiting intracell Ca+ influx)
is used to prevent preterm delivery in patients with a history of preterm delivery and for patients with a shortened cervical length by ultrasoun
Progesterone therapy
is best defined as bleeding leading to symptoms of hypovolemia
> 500 mL blood loss after a vaginal delivery
>1000 mL blood loss after a cesarean delivery
Post partum hemorrhage
*• Hemorrhage is the leading cause of maternal mortality
Whe do we see post partum hemorrhage?
occurs during 3rd stage of labor during delivery of placenta
uterine relaxation during the 4th stage leading to excessive blood loss
- Treated with uterine massage
- Pharmacologic treatment with **oxytocin, prostaglandins, ergot alkaloid **
• Atony
Risk for atony
Precipitous Labor, Large Fetal Weight , Multifetal Gestation, Polyhydramnios, Prolonged Labor, Retained Placenta, Grand Multiparity, Intrauterine Infection, Uterine Relaxation Agents
- Hypovolemia from obstetrical blood loss leads to pituitary infarction or necrosis
- Symptoms may not develop immediately : lactation failure, hypoglycemia, and life threatening hypotension from adrenal insufficiency.
- Symptoms are varied secondary to the many end organ targets of pituitary hormones
Sheehan Syndrome
Pt not contracting after delivery and starting to see lots of blood loss, what may help stimulate contractions and prevent lss of blood?
prostaglandins
