17494
Levonorgestrel is one method of oral emergency contraception , which prevents fertilization and does not disrupt an already established pregnancy ; thus , timing of administration is critical .
 Chemical: Levonorgestrel
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: Levonorgestrel