If your pregnancy is confirmed , then no form of medicines be it ayurvedic , natural , or even allopathic should be used unless it is pregnancy safe. Secondly no medication is advised for first 14 weeks of pregnancy except tab folic acid daily , and if required an antiemetic called doxinate which is pregnancy safe.
Hibiscus usage per se has not be studied and its better not to use it.
I hope i have answered your query in detail,
wishing you good health,
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