Question

A pregnant female was admitted to the labour room. Mild uterine contractions started, but further strong uterine contractions were not taking place. Which of these could a doctor inject to induce delivery?

• A. Oxytocin
• B. Vasopressin
• C. Relaxin
• D. Prolactin

Hint:

Oxytocin is known as the “birth hormone” because it stimulates uterine contractions during childbirth and also helps in milk ejection after delivery.

Answer 1

The Correct Option is A

Concept: Parturition or childbirth is controlled by a complex neuroendocrine mechanism involving hormones and uterine muscular contractions. Oxytocin plays the most important role in stimulating strong uterine contractions during labour.

Step 1: Understanding the beginning of labour pain.
At the end of pregnancy, mild uterine contractions begin due to signals from the fully developed foetus and placenta. These initial contractions indicate the onset of labour.

Step 2: Identifying the hormone responsible for strong contractions.
Oxytocin is secreted by the posterior pituitary gland. It acts directly on the smooth muscles of the uterus and stimulates powerful rhythmic contractions.

Step 3: Understanding the positive feedback mechanism.
When oxytocin causes uterine contraction, these contractions further stimulate release of more oxytocin. This creates a positive feedback cycle that intensifies labour pain and helps in delivery of the baby.

Step 4: Applying the concept to the given situation.
In the question, mild contractions have started but strong contractions are absent. Therefore, doctors inject synthetic oxytocin to induce or strengthen labour contractions and facilitate childbirth.

Step 5: Eliminating incorrect options.
- Vasopressin regulates water balance and blood pressure.
- Relaxin helps relax pelvic ligaments and cervix.
- Prolactin stimulates milk production after childbirth.
None of these hormones induce powerful uterine contractions like oxytocin. Therefore, oxytocin is the correct answer.