Theories Of Labor

Question 1

Theories related to the mother

Answer 1

-Progesterone withdrawal theory : progesterone promotes pregnancy and withdrawal encourages onset of labor
-Oxytocin receptor theory - pressure of presenting part on cervix stimulates the hypophysis to release oxytocin.
-Prostaglandin synthesis theory: decidua and amnion in late pregnancy contains PGs
-Myometrial overstretch theory - uterus becomes stretched due to the growing fetal structures so the pressure increases causing uterine contractions that imitate labor.
-Rising estrogen levels

Question 2

Theories related to the fetus

Answer 2

-Fetal brain theory : Absence of brain resulted in prolonged pregnancies. The key link is the absence of CRF(corticotropin releasing factor)

-Fetal adrenal gland theory: the adrenal gland responds to CRF = ACTH = Cortisol

Question 3

Theories related to the placenta

Answer 3

Placenta clock theory - human placenta produces CRH (similar to CRH from hypothalamus) = ACTH = Fetal DHEA (precursor for placental E2

IUFD leads to initiation of labor

Question 4

Characteristics of normal contractions generated by uterine muscles

Answer 4

Polarity
Fundal dominance
Coordination
Frequency
Duration
Intensity
Resting tone