“We had a baby last night,” the caption reads. “He is perfect and we couldn’t be happier. Stay tuned for a name.”
“I love you, @hilariabaldwin,” he wrote. “My karma is your karma. Your karma is mine.”
Hilaria Baldwin, a fitness entrepreneur and co-host of the “Mom Brain” podcast, shared the news in April that she was pregnant after suffering two miscarriages.
The couple are also the parents of Romeo, 2; Leonardo, who turns 4 on Saturday; Rafael, 5; and Carmen, 7.
Alec Baldwin also shares a 24-year-old daughter, Ireland, with his ex-wife, actress Kim Basinger.