In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Given this life - threatening complication , appropriate prophylactic measures should be used in high - risk woman undergoing ovarian stimulation .
### Output Text:
Given this life - threatening complication , appropriate prophylactic measures should be used in high - risk woman undergoing ovarian stimulation . 