Answer:
The mesoderm layer may have developed abnormally.
Explanation:
During early embryonic development, three germ layers are formed in developing embryo, termed as ectoderm, endoderm, and mesoderm. Germ layer that forms vertebral column in developing embryo is mesoderm.
So, abnormal development of mesoderm would lead to birth of a child with deformed vertebral column. Thus, the correct answer is first option.