Short answer
Yes, cooked plain plantain is safe for pregnant cats in small pieces. Avoid fried or salted varieties as these can upset her stomach. Offer a bite-sized portion occasionally as a treat. If she shows any digestive issues, skip it and check with your vet.
Plantain — Food safety facts
Safe to share · Cats · full breakdown on the linked food page
Cooked, plain plantain is safe in small pieces. Never fried or salted.
The full verdict, portion guidance and serving notes are collected on the Plantain food facts page.