Q. Do you have any resources on pregnancy and chemical substances?

Just using those terms in CloudSearch, I get about 250 results. That is a great number of results but there are hundreds of substances. You'll want to pay attention to the subject headings and play word "detective" as you look through your results. Include the appropriate terms for your assignment. I do recommend using the Advanced Search option. I would not recommend using too many terms otherwise you run the risk of having zero results. Keep a list of those terms to include in search. Also, I recommend marking the terms and search combinations that yield better results.

Use the dropdown option after typing your terms instead of just pressing Enter. If you press Enter, the system will look for your terms but many of them will not actually be about that term. If you select Subject, then the article will most definitely be about that term. A live human actually assigned the subject headings, not some computer-generated algorithm. 

If you get a ton of results, use the filters on the left side of the results to limit. I recommend limiting by year and by Scholarly Peer-Reviewed. That will often cut the results in half or more!