Examination of a 32 year old pregnant woman reveals that she has generalized periodontal probing depths of 4-6mm, most of which bleed on probing. She is otherwise healthy, but asks “If I don’t get the proper periodontal treatment, am I more likely to deliver a pre-term, low-birth weight baby?” Which type of study design would provide the best answer to her question?

A systematic review comparing the risk of delivering pre-term low birth weight babies among women with various risk factors, including the presence of periodontal disease.

Comparing the rates of pre-term low birth weight babies, between women with no risk factors to those with periodontal disease.

A randomized clinical trial of pregnant women with periodontal disease, some of whom receive periodontal therapy and some of whom do not.

A prospective cohort involving pregnant women, some of whom have periodontal disease and some of whom do not.