When rumors started to surface last week that Nicole Richie may be pregnant, I thought to myself "how the heck did that happen?" While she may have gained some weight recently, according to the information provided when she was arrested less than a year ago, Richie is 5'1" and weighs 85 lbs, giving her a BMI of 16.1 which is well under the healthy BMI minimum of 18.

So I figured that the notoriously skinny star was way too thin to conceive, but while being underweight may hinder your chances of getting pregnant, it doesn't make it impossible. However, according to this, she (and other soon-to-be moms who were underweight at conception) should gain up to 40 lbs throughout her pregnancy.

That may seem like a lot for someone so small, but as most future moms would say, if it's good for the baby, it's OK with me. If you're trying to conceive, or are already pregnant and are concerned with weight gain and the effects it will have on your body, take a look here for additional information.