Apple published on its support page that iPhones contain magnets and radios that emit electromagnetic fields, both of which “may interfere” with medical devices such as implanted pacemakers and defibrillators.
Here is the full post:
“iPhone contains magnets as well as components and radios that emit electromagnetic fields. All MagSafe accessories (each sold separately) also contain magnets—and MagSafe Charger and MagSafe Duo Charger contain radios. These magnets and electromagnetic fields might interfere with medical devices.
Though all iPhone 12 models contain more magnets than prior iPhone models, they’re not expected to pose a greater risk of magnetic interference to medical devices than prior iPhone models.
Medical devices such as implanted pacemakers and defibrillators might contain sensors that respond to magnets and radios when in close contact. To avoid any potential interactions with these devices, keep your iPhone and MagSafe accessories a safe distance away from your device (more than 6 inches / 15 cm apart or more than 12 inches / 30 cm apart if wirelessly charging). But consult with your physician and your device manufacturer for specific guidelines.
Consult your physician and medical device manufacturer for information specific to your medical device and whether you need to maintain a safe distance of separation between your medical device and iPhone or any MagSafe accessories. Manufacturers often provide recommendations on the safe use of their devices around wireless or magnetic products to prevent possible interference. If you suspect iPhone or any MagSafe accessories are interfering with your medical device, stop using your iPhone or MagSafe accessories.”