Both AMBOSS and the FDA state that nitrofurantoin is contraindicated from 38 weeks gestation to delivery due to risk of hemolytic anemia. There are no sources that state nitrofurantoin is absolutely contraindicated in the first trimester, although caution is advised.
Sources:
https://next.amboss.com/us/article/mm0VTg?aid=1108db90-a693-469b-b8e5-110219737d5e&guid=i24%2540l%257CT%2525C&uid=8nx2OECPa#Zf8b3037aae5860c291b8fbedeb013514
https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/009175s046lbl.pdf#:~:text=Because%20of%20the%20possibility%20of%20hemolytic%20anemia%20due,or%20when%20the%20onset%20of%20labor%20is%20imminent.
This has now been fixed, thank you for your suggestion!