Katherine Heigl's son was a ''surprise''.

The '27 Dresses' star has confessed that whilst she knew she wanted more children, she didn't know ''how she was going to go about that'' before she welcomed Joshua Bishop Kelley, Jr. into the world last month.

She said: ''It was a surprise! I knew I wanted to expand our family, I knew I wanted to have more children. I just didn't know how we were going to go about that ...

''Pregnancy didn't ever really speak to me. I got really invested in adoption. I didn't look back or even think about it. Only when I was about 35 did I start going, 'Well, should we consider getting pregnant?' You don't want the choice to be taken away from you.''

The 38-year-old actress - who adopted Nancy, eight, and Adalaide, four, with her husband Josh Kelley - found out she was pregnant with Joshua Jr. shortly after she went back to work on her new TV show 'Doubt' and admits her first thoughts were full of panic.

She added: ''I'm one of those people who really thinks, I have to schedule, I have to plan this out. I'll be totally honest, my first reaction was 'Oh s**t.' But now we have a new normal, and I have to give myself a break in order to get used to it.''

And Katherine hasn't ruled out getting pregnant again but is ''very inspired'' by adoption.

She shared: ''I'd get pregnant again, and I still am very inspired by adoption. I also have been thinking a lot about fostering. It's all up in the air. And I'm okay with that!''

The blonde beauty is thrilled to have little Joshua - her first son - in her life and the whole family is ''really obsessed'' with him.

She told the new issue of People magazine: ''We're at the point where we're really obsessed with him! With a newborn, you're forced to be still ... and you have this beautiful reason to do that.''