The 61-year-old actor already has four children aged six and under with his 35-year-old wife and they are "so happy" to hear a heartbeat following their heartbreaking loss, reports mirror.co.uk.
After sharing the tragic news of the miscarriage live on social media, Hilaria was happy to share the more joyful news that she was expecting.
Writing alongside a video of the baby's heartbeat on Instagram , she said: "It is still very early but we have learned that there is a little person inside of me. The sound of this strong heart makes me so happy especially because of the loss we experienced in the spring. We want to share this news as we are excited and don't want to hide the pregnancy."
She added: "These first few months are tough with exhaustion and nausea and I don't want to have to pretend that I feel ok. My one request is that the media not send paparazzi to follow me or buy independent paparazzi photos, hence encouraging them."
"I want to remain peaceful during this very early time in my pregnancy and getting chased around by cameras is not in the doctor's orders."
The newest addition to the family will join brothers Romeo Alejandro David, 16 months, Leonardo Angel Charles, three, and Rafael Thomas, four, as well as sister Carmen Gabriela, six.
Alec also has a 23-year-old daughter, Ireland, with former wife Kim Basinger.
He also shared the news on Instagram by posting the same video and captioning it: "Well, I am delighted to say, 'Uno mas Baldwinito,' God is good."
( With inputs from IANS )