Apple has always warned that its iPhone 12 lineup and MagSafe accessories could interfere with medical devices, like pacemakers and defibrillators. Now the company has released additional guidelines for those who use medical devices.
In a support article, Apple explains that iPhones contain magnets, components, and radios that emit electromagnetic fields, which pose a risk to medical devices. All iPhone 12 models contain more magnets than prior iPhone models, but they aren't expected to post more of a risk to medical devices—although it's still best to keep your medical devices away from your iPhone.
It's also important to keep medical devices away from all MagSafe accessories, including chargers, as they also contain magnets and radios.
"Medical devices such as implanted pacemakers and defibrillators might contain sensors that respond to magnets and radios when in close contact," Apple noted. "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."
To sum things up, keep your iPhone 12 (but really all iPhone models) and MagSafe accessories away from your medical devices.