The 42 year old shed a few pounds during intense training for the 2003 action thriller, prompting her stylist to take her tight yellow body suit in an inch to hug Thurman's new figure.
The actress subsequently fell pregnant, giving birth to her son Levon just months before the actual shoot, and Thurman admits she didn't have enough time to get her slimline figure back, which caused a slew of problems.
She tells Elle magazine, "I'd just had my son, and I was trying to get back in shape. I was trembling - I barely made it...
"I'll never forget walking onto the set the first day of shooting having had my costume taken in an inch a week during the training period and just barely making it to the opening shot with the bulges tamed... The hundred days in my yellow suit were some of the toughest I've ever had to get through and some that I'm most proud of."