Onset of labour is initiated by which of the following? 1. Uterine distension 2. Increased CRH and ACTH from foetal hypothalamic-pituitary- adrenal axis 3. Increased level of progesterone immediately before labour 4. Increased synthesis of myometrial receptors for oxytocin due to effect of oestrogen Select the correct answer using the code given below.
Factors Initiating Labour Onset
The process initiating labour involves several physiological triggers. Understanding these factors is key:
- Uterine distension: Mechanical stretching of the uterine walls, particularly in the later stages of pregnancy, stimulates uterine contractions.
- Fetal Hypothalamic-Pituitary-Adrenal (HPA) Axis Activation: Increased fetal production of CRH and ACTH from the fetal adrenal glands plays a crucial role in signalling the onset of labour.
- Oestrogen Effects on Myometrium: Elevated oestrogen levels enhance the synthesis and sensitivity of oxytocin receptors on the myometrial cells. This makes the uterus more responsive to oxytocin, a hormone essential for contractions.
Incorrect Factor in Labour Onset
One factor often cited, but incorrectly related to *initiation*, is progesterone:
- Progesterone Level Changes: A functional *decrease* or withdrawal of progesterone's inhibitory effect on the uterus is necessary for labour to begin. An *increase* in progesterone immediately before labour would typically prevent contractions.
Identifying the Correct Combination
Evaluating the statements provided:
- Statement 1 (Uterine distension) is a recognised trigger.
- Statement 2 (Increased fetal CRH and ACTH) is a recognised trigger.
- Statement 3 (Increased progesterone) is physiologically incorrect for labour initiation.
- Statement 4 (Increased oxytocin receptors due to oestrogen) is a recognised trigger.
Therefore, the correct factors initiating labour are uterine distension, fetal axis activation (CRH/ACTH), and increased oxytocin receptors.
This corresponds to statements 1, 2, and 4 being correct.
The correct option is Option 2.
Important Questions from Normal Labour
Which of the following features are correct regarding onset of true labour?
1. Regular uterine contractions
2. Progressive cervical dilation and effacement
3. Presence of show
4. Labour and delivery are synonymous
Select the answer using the code given below.
- According to the WHO Intrapartum Care Guidelines, 2018, the active phase of labour starts from what dilation of cervix?
- The normal rate of dilatation of the cervix in a primigravida in the active phase of labor is
- Regarding the phenomenon of 'lightening' in primigravida at term pregnancy, which one of the following statements is correct?
- In the mechanism of normal labour the engaging transverse diameter is
