Long before the TomKat and Brangelina “bumpwatch” began, designer Liz Lange targeted expectant stars as the next big thing in helping to market her line of sophisticated maternity wear to the masses.

“When pregnant celebrities show up on the red carpet in sexy fitted clothing, it makes other women want to dress that way,” says the Gotham-based designer.

Lange opened her first boutique on the Upper East Side in 1997 and began courting Mommywood in earnest. “Nobody else was doing it, so it was extremely easy,” says Lange, who also has a Beverly Hills boutique and a line at Target. “Anytime I’d hear that someone was pregnant, I would just get to them through their agents or assistants and ask, ‘Can I dress you?’ Across the board they’d say, ‘Sure.’ ”

Her client list would make any tenpercenter green with envy. Katie Holmes, Jennifer Garner, Gwyneth Paltrow and Angelina Jolie are all fans of her body-conscious sportswear.

The former Vogue editor says she has a special bond with Hollywood moms-to-be because “I always feel badly for them when I’m in the dressing room with them because they’re at such a sensitive stage. They’ve very vulnerable.”

Their biggest challenge, says Lange, is looking good 24/7. “There’s no place they’re ‘safe’ from the cameras today,” she says. “These days, their ‘I’m going to Starbucks’ outfit comes into question.”

Lange recently launched 4th Trimester, her postpartum line, and scored big at this year’s Oscars.

New moms Tracey Stewart (host Jon’s wife) and producer Caroline Baron (nominated for best picture for “Capote”) wore custom creations the designer whipped up days after the women gave birth.

“Nobody bounces right back after a baby,” says Lange. “But that doesn’t mean you can’t look like a star.”