Need help with pre-pregnancy weight gain guidelines for women who are over their recommended trimester weight.

Hello, I have searched and searched and searched for weight guidelines for pregnant women who are above their recommend trimester weight based off of their pre-pregnancy weight. Let me give you an example to better clarify my question. Let's say we have a woman with a prepregnancy weight of 140 lbs and she is 5'5. She is in her 3rd trimester on day 206 but she weighs 180 lbs. Her maximum allowable weight gain based on her prepregnancy BMI would be 175 lbs (uming at the end of the trimester). Now on average, this woman would need to eat about 384 kcal a day to gain the "average" recommended during her 29th week of pregnancy on day 206. What I'm wondering is, without prescribing that the woman lose weight, what would be an acceptable caloric restriction for this and other women? What if the woman was in her 2nd trimester and had "room to grow" but is still overweight based off her prepregnancy BMI? Is there a mathmatical formula or algorithm for calculating this weight gain guideline?