The Without Me singer, who is expecting her first child with the screenwriter, marked the special occasion on Instagram with a snap of Alev kissing her bare baby belly.
Alongside the sweet image, the mother-to-be wrote in the post on Wednesday: “Iyi ki dogdun happiest birthday, askim… @zoneaydin”.
The Turkish message roughly translates to, “Happy birthday happiest birthday, my love (sic).”
Alev replied by commenting, “I love you, angel… my favorite person…”
Halsey stunned her fans and followers in January when she announced that she and the 37-year-old screenwriter were expecting their first child together.
The 26-year-old musician has spoken about her fertility issues in the past, and revealed she underwent surgery more than three years ago for endometriosis, which previously caused her to suffer a series of miscarriages.
Now Halsey is preparing to be a first-time mother, and insisted the pregnancy was “100 per cent planned”, even though news of the relationship with Alev only emerged in October.
She said she managed to keep her pregnancy a secret for so long after having to cancel her Manic tour due to the coronavirus pandemic.