Consider the following statements regarding the cause for onset of labour : Statement 1 : Alteration in estrogen-progesterone ratio results in prostaglandin synthesis and onset of labour. Statement 2 : Decreased fetal production of dehydroepiandrosterone sulfate (DHEA-S) and cortisol inhibits the conversion of fetal pregnenolone to progesterone. Which one of the following is correct with respect to the above statements?
Statement 1 is true but Statement 2 is false
The correct answer is Statement 1 is true but Statement 2 is false. Statement 1 states the functional progesterone-withdrawal theory: near term a rise in the oestrogen-to-progesterone ratio ends myometrial quiescence, increasing gap junctions (connexin-43), oxytocin receptors and calcium channels, and activating decidual phospholipase A2, which liberates arachidonic acid and generates prostaglandins E2 and F2-alpha, which ripen the cervix and drive coordinated contractions.
Statement 2 is false because it reverses the physiology. Near term, maturation of the fetal hypothalamo-pituitary-adrenal axis increases adrenal DHEA-S and cortisol. DHEA-S is aromatised by the placenta to oestriol, raising the oestrogen-progesterone ratio, while cortisol up-regulates placental CRH and prostaglandins. The fetal steroid surge therefore promotes labour, so both options calling statement 2 true, and the option calling statement 1 false, are wrong.
Key point: The sequence is fetal HPA activation, rising oestrogen-progesterone ratio, prostaglandin release, oxytocin receptor up-regulation, contraction.
Similar Questions
Consider the following statements regarding the WHO Labour Care Guide for labour monitoring :
1. Active phase starts from 5 cm of cervical dilatation.
2. There is fixed rate for dilatation for every hour of labour in active phase.
3. There are no alert or action lines on the partograph.
4. There is a separate section for intensive monitoring for second stage of labour as well.
Which of the statements given above are correct?
Important Questions from Normal Labour
- Which one of the following is NOT a component of active phase in the partograph?
- The components of partograph are all EXCEPT:
- Which of the following information are provided by partograph?
1. Colour of liquor
2. Uterine contractions with duration and frequency
3. Dilatation of cervix
Select the correct answer using the code given below: - Which one of the following is NOT a sign of separation of placenta?
- Consider the following cardinal movements of mechanism of normal labor:
1. Engagement
2. Internal rotation
3. Flexion
4. Restitution
5. Crowning
6. External rotation
What is the correct sequence of movements in labor in occipito-lateral position?
