On Wednesday 8 January, the Canadian singer shared a picture on Instagram, which shows her posing nude with a digitally-superimposed image of a foetus visible through her translucent stomach.
Several of Grimes’ one million followers on the social media platform interpreted the image as a pregnancy announcement, including a number of her music industry peers.
“Congraaaaats,” wrote fellow singer Tove Lo, while artist Janelle Monae commented with a series of celebratory emojis.
Grimes first shared the image with her nipples visible, and replied to an Instagram user's comment explaining she initially considered censoring the image in line with the platform's nudity policy, but "being knocked up" is a "very feral and war-like state of being".
She later deleted the image and re-shared a censored version, still showing the foetus.
Neither 31-year-old Grimes nor 48-year-old Musk are yet to share official statements regarding the supposed pregnancy announcement.
The celebrity couple revealed in May 2018 that they had become romantically involved, making their first public appearance at the Met Gala.
Musk reportedly helped to design Grimes’ gothic-style ensemble for the event, which featured an ombre, grey bodice and a black train.
The technology entrepreneur had six children with his ex-wife, Justine Musk, to whom he was married from 2000 to 2008.
Their first son, Nevada Alexander Musk, died in 2002 when he was 10 weeks old of sudden infant death syndrome.
They later conceived twin boys, Griffin and Xavier, in 2004, and triplets Damian, Saxon and Kai, in 2006, via IVF.