Which of the following change does not occur during parturition ?

Options

A. Progesterone secretion stops
B. Pituitary gland secretes oxytocin
C. Relaxin contracts the pubic symphysis
D. Oxytocin induces contraction in uterus

Answer

To answer the question "Which of the following change does not occur during parturition?", we need to analyze the physiological changes that take place during the childbirth process, known as parturition.

### Step-by-Step Solution:

1. **Understanding Parturition**:
- Parturition is the process of childbirth, which involves a series of physiological changes in the mother’s body to facilitate the delivery of the baby.

2. **Role of the Fetus and Placenta**:
- The process begins when the fully developed fetus and the placenta send signals to the maternal pituitary gland.

3. **Hormonal Changes**:
- The posterior pituitary gland secretes oxytocin in response to these signals. Oxytocin is crucial as it stimulates contractions of the myometrium (the muscle layer of the uterus).

4. **Contraction of the Uterus**:
- The contractions of the uterus become more vigorous as parturition progresses, leading to the delivery of the baby.

5. **Relaxin and Pubic Symphysis**:
- Relaxin is a hormone that helps to relax the pubic symphysis, allowing for the widening of the pelvis during childbirth. Therefore, it does not contract the pubic symphysis; it actually facilitates its relaxation.

6. **Other Hormonal Changes**:
- During parturition, the secretion of progesterone decreases, which is a necessary change for the labor process.

7. **Identifying the Incorrect Statement**:
- Among the options provided, the statement that "relaxin contracts the pubic symphysis" is incorrect because relaxin actually relaxes it.

### Conclusion:
The change that does not occur during parturition is: **"Relaxin contracts the pubic symphysis."**