The Australian supermodel teased the important news on the platform her husband, Snapchat CEO Evan Spiegel, runs.
The 40-year-old posted a few snaps to her profile, starting with one of her side profile, caressing her bump. Wearing a summery white top and low cut jeans to show off her bump, she wrote, “So excited to announce baby number 4”.
In the next photo, she faced the camera as she held her bump with both hands, adding in the caption, “And it’s a boy”.
The next sweet photo in the series includes photos of four different pairs of yellow shoes, numbered one through four from biggest to smallest, symbolising her four sons. “#boymum”, she wrote alongside the cute image.
This next child will be her third with husband Spiegel, with the pair already sharing sons Hart, five, and Myles, three after getting married in 2017.
She also shares a son with her ex-husband, actor Orlando Bloom, a 12-year-old named Flynn.
Kerr previously spoke about the effect her pregnancies have on her body and what that means to her as a model.
Speaking to Vogue Australiathe former model said she felt “grateful” to be able to model again, but that things aren’t exactly as they were.
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“I still don’t feel like I’m back to where I was before the babies,” she admits. “But I’m content with that.
“My body is different and it has changed, and I’m embracing that.”