1155
The excess event rate was 1 . 8 per 1 , 000 woman - years ( 95 % CI - 0 . 5 - 4 . 1 ) , and the number needed to treat to cause 1 event was 170 ( 95 % CI 100 - 582 ) over 3 . 3 years .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 None