What are the major features of embryonic development at the By the end of 12 weeks (first trimester) of pregnancy?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Timeline of Pregnancy:**
- Pregnancy is typically divided into three trimesters, each lasting about three months or 12 weeks. By the end of the first trimester, significant developments occur in the embryo.

2. **Heartbeat Detection:**
- By the end of the first month (approximately 4 weeks), the heartbeat of the embryo can be detected. This is an important milestone as it indicates the establishment of circulation and the functioning of the heart.

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