Recommended pregnancy weight gain is based primarily on your pre-pregnancy BMI, whether you're carrying a singleton or twins, and your stage of pregnancy. These guidelines come from the Institute of Medicine (IOM), which studied outcomes across a large population to identify gain ranges associated with healthy pregnancies.
Your pre-pregnancy BMI places you into one of four categories, each with a different recommended range \u2014 lower BMI categories are generally advised to gain more, and higher BMI categories less, since starting weight already factors into overall pregnancy weight:
Most of this gain happens in the 2nd and 3rd trimesters, following a fairly steady weekly rate, while first-trimester gain is typically minimal. Not sure of your pre-pregnancy BMI? Use the BMI Calculator first, then come back here.