I didn’t found proven information that easy backbends can be harmful during pregnancy.
Some guidelines contain easy backbends, so if you had this experience before pregnancy and your ob-gyn has nothing against your prenatal practice, and its’s comfortable for you it’s pretty safe to perform easy backbends. My own experience as a mother and as a physician who works with pregnant women shows it’s better to practice slight backbends than don’t)
Please avoid deep backbends if you are seriously overweight, if you had diastasis recti abdominis after previous pregnancies, and if you feel uncomfortable doing b-bends.
Always listen to your body, your practice and intuition are a good guides, every woman has an unique body and different experience of pregnancy.
Look at my fave b-bends for II trimester: video