Parturition Flashcards
What changes happen to the uterus in the pregnancy?
Increase in size: 4-70 grams to 1200 grams (not including the fetus)
Myometrial proliferation in early pregnancy
Myometrail hypertrophy in later half of pregnancy
Gap junctions between myometrium
Major increase in blood supply: From 2% of CO to 17% (Greater than the brain)
What type of contractions are uterine contractions?
What is their mechanism?
Spontaneous contraction: No need for hormonal or nervous input
AP results in intracellular calcium increase
Calcium-calmodulin binding
Myosin light chain kinase activation allowing cross-bridging
What transition needs to occur for myometrial cells to properly occur?
Transition to a labor phenotype
Shift from progesterone dominance to estrogen dominance
Which hormones affect uterine contractility and how?
Progesterone
Inhibition intracellular calcium entry, SR release
Membrane hyperpolarization via K channels
Inhibits gene expression for pro-contraction
Levels are constant before and during labor
Estrogen
Increases gap junctions to promote synchrony
Increases oxytocin receptor and prostaglandin receptor expression in myometrium
What pathways are involved in utterine contractions?
Uterine stretch and estrogen upregulate contraction-associated proteins (CAP)
Initiate excitation: GPCRs via PLC pathway
Increase frequency and amplitude of contractions
What are the CAPs?
Gap junction connexin-43
Oxytocin receptor
Corticotropin-releasing hormone receptor
COX-2
What are the triggers for labor?
Fetal adrenal gland plays an important role: fetal signal
Fetal HPA axis is immature
Maturity of HPA thought to induce contractions
Increased maternal estrogens
Increased PGs
Increase in CAP
What is the definition of labor?
Regular contractions leading to cervical dilation over time
What is pre-term labor defind as?
What are the causes?
Pre-term: 20-37 weeks gestation
Uterine distension: CAP, CRH, Estrogen, Oxytocin all increase
Infection: Toxins stimulate cytokines stimulating PGs
Preterm premature rupture of membranes: Apoptosis of cellular component of fetal membrane, MMPs play a role
Maternal-fetal stress: Premature rise in cortisol and estrogens can induce labor phenotype and stimulate fetal adrenal c19 hormones
What is the public health correlation with pre-term births?
Leading cause of infant mortality and long term neurological disabilities
Preterm delivery rates lowest in Europe (6.2%), highest in Africa (11.9%)
12.1% in US
African-American concentration influences this and infant mortality most
What are the risk factors of pre-term labor?
Preterm delivery rates lowest in Europe (6.2%), highest in Africa (11.9%)
12.1% in US
African-American concentration influences this and infant mortality most
What pharmacological agents are involved in pre-term labor?
Magnesium, Beta-2 Agonist, Calcium Channel Blockers, Prostaglandin synthesis inhibitors: All act by blocking calcium influx
Progesterone therapy to prevent in patients with a history of preterm delivery and for patients with a shortened cervical length by ultrasound
What is the definition of post-partum hemorrhage?
When does it occur and why?
Leading cause of maternal mortality
Definition: Symptomatic of hypovalemia
>500 mL after vaginal delivery
>1000 mL after cesarean delivery
Occurs during 4th stage of labor: Constant myometrial contraction necessary to limit blood loss
Uterine atony – Lack of contraction
What are classic risk factors for atony?
Precipitous or prolonged labor
Polyhydraminous
Large fetal weight
Multifetal gestation
Retained placenta
Grand multiparity
Intrauterine infection
Uterine relaxation agents
Treated with uterine massage
What are the pharmacologic treatments for post-partum hemorrhage?
Oxytocin, PGs, ergot alkaloid
