AceShowbiz -

Leelee Sobieski and her fashion designer husband Adam Kimmel have welcomed their second child together. Her representative told PEOPLE that son Martin was born in July, while Us Weekly reported the baby was born in August.

The "Joan of Arc" alum showed off her post-pregnancy body at the Museum of Modern Art Film Benefit on Monday evening, November 10. In some pictures obtained by Mail Online, Leelee accentuated her trim waist in a black flared mini dress.

Leelee previously kept mum about her second pregnancy and never actually made an official announcement. Her pregnancy was revealed after she stepped out to attend the Christian Dior Cruise 2015 fashion show at the Brooklyn Navy Yard in NYC with a very visible baby bump back in May.

Leelee and Adam, who got married in an intimate wedding in Italy back in 2010, are already parents to 4-year-old daughter Louisanna Ray whom they adoringly call "Lewi."

The "NYC 22" alum previously told PEOPLE of motherhood after welcoming Lewi, saying, "I just can't believe I'm a mom. It's weird! You look at your own mom differently. I realized, 'You changed all my diapers? You did that?' You really appreciate your mom."