Question: when does the uterine lining become more vascular
[{'answer': 'During pregnancy', 'provenance': [{'wikipedia_id': '9509', 'title': 'Endometrium', 'start_paragraph_id': 1, 'start_character': 405, 'end_paragraph_id': 1, 'end_character': 421, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '9509', 'title': 'Endometrium', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 691, 'bleu_score': 0.9106679819523871, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2511082000616182357}, 'section': 'Section::::Abstract.'}]}]