Some Apple Watch users who upgrade to the Series 12 or the Ultra 4 might temporarily lose access to hypertension notifications.

On the watchOS feature availability page, Apple says notifications might not be available on the Series 12 or Ultra 4 at launch because regulatory clearances are in process.

Hypertension Notifications may not be available on Apple Watch Series 12 or Ultra 4 in your region, as additional regulatory clearances for these devices are in process.

The warning applies to 33 countries and regions, including Canada, Australia, India, Brazil, Singapore, Japan, Taiwan, South Africa, South Korea, and the UAE, with a full list on Apple's website.

The Apple Watch Series 12 and Apple Watch Ultra 4 have revamped sensors and a new Health Sensing System. Apple added new optical and electrical heart sensors for more frequent and accurate tracking, and the change appears to require new regulatory approval in some locations.

What's new:

• ECG - The electrodes in the watch cover more surface area for improved skin contact during ECG readings.
• Optical sensing - Redesigned photodiodes are organized in a ring to capture light more efficiently.
• Heart rate measurement - Larger, power-efficient green LEDs in the optical heart rate sensor allow the new watches to measure heart rate every five seconds all day, offering more data on a user's fitness and physiological state. Real-time heart rate is available in the updated Heart Rate app, and Exercise and Move Activity rings are more accurate. HRV is also measured as often as every five minutes.

Apple Watch users who get these notifications today may lose the option when upgrading to the Series 12 or Ultra 4 until regulatory clearance is granted.

Countries not on Apple's list with a footnote will continue to get notifications as usual. This includes the United States, UK, and all EU countries.