Question: when do neural tube defects occur during pregnancy
[{'answer': 'the 3rd week'}, {'provenance': [{'wikipedia_id': '3202774', 'title': 'Neural tube defect', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 359, 'bleu_score': 0.92860998190983, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13171435446096895517}, 'section': 'Section::::Abstract.'}]}]