A temporary family planning method based on the natural effect of breastfeeding on fertility is due to the high level of:

Options

A. Progesterone
B. Prolactin
C. Estrogen
D. FSH

Answer

To solve the question regarding the temporary family planning method based on the natural effect of breastfeeding on fertility, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about a temporary family planning method that relies on the natural effects of breastfeeding on fertility.

2. **Identifying the Method**: The method referred to is known as "lactation amenorrhea." This term combines "lactation," which is the process of breastfeeding, and "amenorrhea," which means the absence of menstruation.

3. **Explaining Lactation Amenorrhea**: During breastfeeding, especially in the initial months after childbirth, a woman's body experiences a natural suppression of ovulation. This is primarily due to hormonal changes that occur during lactation.

4. **Role of Prolactin**: The hormone responsible for this effect is prolactin. Prolactin levels increase significantly during breastfeeding, which inhibits the release of hormones necessary for ovulation.

5. **Duration of Effectiveness**: It is important to note that lactation amenorrhea is effective as a birth control method typically for up to six months postpartum (after giving birth). After this period, its effectiveness decreases.

6. **Conclusion**: Therefore, the high level of prolactin during intense lactation is what makes this temporary family planning method effective in preventing ovulation and thus serves as a natural form of birth control.

### Final Answer:
A temporary family planning method based on the natural effect of breastfeeding on fertility is due to the high level of **prolactin**.

---