Bryce Dallas Howard won't reveal the sex of her baby.

The 30-year-old actress and her husband Seth Gabel know whether they are expecting a brother or sister for four-year-old son Theo but are reluctant to share the news.

She said: "We do know - we didn't know for a while. We just found out recently. At this point we're telling just family."

Bryce had a "tough" start to her pregnancy but now she is enjoying the later stages and is just hoping she and the baby can stay healthy.

She told Canada's 'Entertainment Tonight': "It's kind of euphoric. It's the greatest, I love it. The thing that every parent hopes for is that the baby's healthy, I'm healthy. No matter how you feel, that's the most important thing."

The 'Terminator Salvation' star also admitted she expects to slow down after she gives birth before the end of the year.

She added: "Whether you intend to slow down, you slow down. My son will be five [in February] and that time is so crucial for him and as a family."

Despite being six months pregnant, Bryce is busy promoting two movies, '50/50' and 'Restless', and she recently admitted she has taken Steps to ensure she is comfortable, even on glamorous occasions.

She said: "I wear very comfortable shoes. I wore flip-flops the other night on the red carpet. That was very comfortable."