Which is not a risk factor for having a baby with low birthweight?

One factor that is not typically considered a risk factor for low birthweight is a mother's advanced age, specifically women over 35, as they can have healthy pregnancies. While advanced maternal age can introduce other risks, it does not directly correlate with low birthweight in the same way that factors like smoking, poor nutrition, or multiple pregnancies do. It's important to consider a comprehensive range of factors when assessing risk.