Perhaps you should try some spelling variations:
"improving maternal performance metrics." » "improving materials performance metrics.", "improving external performance metrics.", "improving national performance metrics.", "improving maternal performance measures.", "improve maternal performance metrics.", "improving water performance metrics."
"improving animal performance review." » "improving annual performance review.", "improving thermal performance review.", "improving fiscal performance review.", "improving animal performance risk.", "improving animal performance evidence.", "improving initial performance review.", "improving optimal performance review.", "improving criminal performance review."

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving maternal performance metrics.") or ("improving animal performance review."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving maternal performance metrics.") OR ("improving animal performance review."))*.
• Removing quotes may allow a broader search: (( improving maternal performance metrics. ) or ( improving animal performance review. ))*.