In March 2021, Apple issued a support document that downplayed the risk the magnets in the iPhone 12 could have on such medical device:
“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,” the document used to read. (You can still read a cached copy here).
The document recommended keeping the “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).”
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The updated document has been expanded and now recommends that the following products should be kept a safe distance away from a medical device such as implanted pacemakers and defibrillators.
AirPods and Charging CaseAirPods and Wireless Charging Case AirPods Pro and Wireless Charging CaseAirPods Max and Smart CaseApple WatchApple Watch bands with magnetsApple Watch magnetic charging accessoriesHomePod HomePod miniiPadiPad miniiPad AiriPad ProiPad Smart Covers and Smart FoliosiPad Smart Keyboard and Smart Keyboard FolioMagic Keyboard for iPadiPhone 12 modelsMagSafe accessoriesMac miniMac ProMacBook AirMacBook ProiMacApple Pro Display XDRBeats FlexBeats XPowerBeats ProUrBeats3
The advice for safe distances remains the same: 6 inches/15 cm or more than 12 inches/30 cm apart if wirelessly charging.