Parturition, Lactation, and Neonatal Physiology Flashcards
Reciprocal changes between what two hormones are necessary for the onset of labor?
Progesterone and estrogen
Progesterone blocks contractions normally. So to give birth, how does this change?
How does estrogen help the labor process?
Progesterone receptors on the uterus become desenstized to the hormone
this leads to an increase in estrogen receptor expression
More estrogen binds and allows for an increase in myometrial contraction and cervical dilation
How do prostaglandins help with labor?
- Synthesis of prostaglandins is stimulated by estrogen, fetus, and contractions
- PGF2a potentiates oxytocin induced contractions by increasing gap junction formation
- Result is increased uterine contractions and cervical dilation
How does oxytocin help with labor?
- UTerus is insensitive to oxytocin until 20wks
- estrogen receptors increase oxytocin receptors
- help the myometrium contract and stimulates decidual tissue to produce PGF2a
What is the Ferguson Reflex?
during active labor, Oxytocin stimulates uterine contractions
this stimulates PGF2a production
This stimulus for this is cervical distension and these produce further cervical distension/dilation which drives the Ferguson Reflex (positive feeback loop to enhnace labor)
How does Relaxin help with labor?
- cytokine similar to insulin
- may help keep the uterus quiet during prengnacy and help to soften/dilate cervix toward end of pregnancy
What are the mechanical changes of labor?
- uterine size
stretch of Sm. M increases Ferguson reflex and furthers contractions and stimulates prostaglandin production
- Cervical remodeling
structural changes resulting in change from fetal support to birth canal
How is labor initiated?
Stress.
Placental produces CRH which increases contractions and accumulates in fetus
Fetus makes ACTH which increases fetal cortisol and placental CRH release
Fetal placental estrogen increases to enhance myometrial contractility
so stress causes labor. don’t be stressed.
What are the changes of the uterus and cervix during contractions?`
fully dilated cervix is drawn up just below the pelvic inlet
subsequent uterine contractions push fetus downward through the pelvis
first stage is longest, second stage usually less than an hour followed by placental delivery
How is the placenta delivered?
uterus contractions reducing area of attachement
sepration of uterus and placenta causes bleeding and clotting
oxytocin helps constrict blood vessels (synthetic given, or nipple stimulation can cause release of oxytocin-nursing)
What is the fetal stimuli for breathing after birth?
asphyxiation during birth
sudden drop in temperature/cooling
What are the causes for delayed breathing upon birth?
use of general anesthesia during delivery
prolonged labor
head trauma
Describe the baby’s first breath after birth?
alveoli are collpased and filled with fluid
more than 25mmHg negative inspr. pressure needed to overcome surface tension and open alveoli
first breath infant capable of -60mmHg and brings in about 40ml of air
deflation of lungs requires strong positive pressure to ovecome viscous resistance of fluid in bronchioles
Blood flow to the placenta shunts blood away from where?
How so?
blood is shunted away from the lower trunk in order to reach placenta
Umbilical arteries with lots of branches, capillary network returns deoxygenated blood.
Legs blood flow is connected to IVC
What does the umbilical vein do>
returns oxygenated blood to fetus from placenta
blood enters via ductus venosus