Question

A local group of obstetricians (OB/GYNs) has hired your team to conduct a cohort study among pregnant women seen at their three satellite offices. The study is intended to find out whether a mother’s body mass index (BMI) at 12 weeks gestation influences her risk for preterm delivery. Over a period of six months, you enrolled 600 pregnant women during their first OB appointment at one of the three satellite offices. Women were excluded from the study if they were determined to be beyond 12 weeks gestation at their first appointment or they had a previous pregnancy that resulted in a preterm delivery (before 36 weeks gestation). The BMIs of all participants were measured at 12 weeks gestation and 98 women were considered to have a high BMI (25.0 or greater). After following all of the participants through delivery without any loss to follow-up, you found that 52 women delivered preterm infants, 20 among those who had a high BMI.

How will you set up the 2X2 contingency table for the data?

Answer 1

To create a 2x2 contingency table, categorize participants by their BMI and delivery outcome. Two rows represent high and not high BMI, and two columns represent preterm and full-term deliveries. Fill the table with data, totaling 98 women with high BMI (20 had preterm deliveries) and 502 with a not high BMI (32 had preterm deliveries).

Step-by-step explanation:

To set up a 2x2 contingency table for the data obtained from the cohort study on pregnant women, we need to categorize the participants based on their BMI (high or not high) and the outcome, which is whether they had a preterm delivery. The table has two rows representing the BMI categories: high BMI (≥ 25.0) and not high BMI (< 25.0), and two columns representing the outcomes: preterm delivery and full-term delivery.

Contingency Table Setup

BMI Category Preterm Delivery Full-term Delivery High BMI (≥ 25.0)2078 (98 total - 20 preterm)Not High BMI (< 25.0)32 (52 total preterm - 20 with high BMI)470 (600 total - 98 with high BMI - 32 preterm with not high BMI)

The table counts 98 women with a high BMI, out of which 20 had preterm deliveries. For the women with a BMI less than 25, we subtract the 98 women with a high BMI from the total 600 to find that 502 women were in this category. Then, we subtract the 20 preterm deliveries with high BMI from the total 52 preterm deliveries to find that 32 women with a not high BMI also had preterm deliveries, leaving 470 who had full-term deliveries.