Anatomy Neural tube formation occurs on A 18 to 23 days post fertilization and is the second stage of craniofacial development B 28 to 38 days post fertilization and is the third stage of craniofacial development C 42 to 55 days post fertilization and is the fourth stage of craniofacial development D 17th day post fertilization and is the first stage of craniofacial development 💡 Explanation Neural tube formation occurs on ✓ Correct Answer: A. 18 to 23 days post fertilization and is the second stage of craniofacial development