Which of these is not an important component of initiation of parturition in humans?

Options

A. Increase in oestrogen and progesterone ratio
B. Synthesis of prostaglandins
C. Release of oxytocin
D. Release of prolactin

Answer

To determine which component is not important for the initiation of parturition in humans, let's analyze the options provided:

1. **Increase in estrogen and progesterone ratio**:
- During parturition, there is a shift in the balance of hormones, particularly an increase in estrogen relative to progesterone. This change is crucial as it helps to prepare the uterus for contractions. Therefore, this is an important component.

2. **Synthesis of prostaglandin**:
- Prostaglandins are released by the placenta and play a significant role in stimulating uterine contractions. They help to initiate labor and facilitate the process of parturition. Thus, this is also an important component.

3. **Release of oxytocin**:
- Oxytocin is known as the "delivery hormone." It is released from the pituitary gland and is essential for stimulating uterine contractions during labor. This is a critical component of parturition.

4. **Release of prolactin**:
- Prolactin is primarily involved in milk production and lactation, not in the initiation of labor. While it is an important hormone for breastfeeding, it does not play a direct role in the process of parturition.

Based on this analysis, the answer to the question is **D: release of prolactin**, as it is not an important component of the initiation of parturition in humans.

### Step-by-Step Solution:
1. **Understand the process of parturition**: Recognize that parturition is the delivery of a baby, which involves a complex neuroendocrine mechanism.
2. **Evaluate each option**: Analyze each of the provided options to determine their relevance to the initiation of parturition.
3. **Identify key hormones**: Focus on hormones that are directly involved in labor, such as estrogen, progesterone, prostaglandins, and oxytocin.
4. **Determine the irrelevant component**: Conclude that prolactin is primarily associated with lactation and does not play a role in initiating labor.
5. **Select the correct answer**: Identify D (release of prolactin) as the correct answer to the question.