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: Its use in pregnancy , however , is an open question as a number of detrimental side effects have been reported in the fetus and neonate .
### Output Text:
Its use in pregnancy , however , is an open question as a number of detrimental side effects have been reported in the fetus and neonate . 