Estimating the relative risk of low birth weight (BW) compared to normal BW by physician visit during the first trimester

Below is a table that presents the primary data for our investigation:

We are interested in estimating the relative risk of low birth weight (BW) compared to normal BW by physician visit during the first trimester (Hint: “no physician visit during the first trimester” is the exposed group; and “one or more” is the reference group), stratified by the presence (yes) or absence (no) of a co-morbidity (history of premature labor, hypertension, uterine irritability).

 

 

 

Physician Visit First Trimester

 

(A)

 

Co-morbidity Present (Z)

 

   

No

 

Yes

 

   

Low BW

 

Normal BW

 

Total

 

Low BW

 

Normal BW

 

Total

 

None

 

(Exposed group)

 

26

 

63

 

89

 

45

 

5

 

50

 

One or more

 

(reference group)

 

17

 

59

 

76

 

6

 

8

 

14

 

 

 

 

 

a. Calculate the relative risk (RR) and attributable risk (AR) for each subgroup, defined by the presence or absence of a known co-morbidity. (Remember: “one or more physician visit during first trimester” is your reference group) (2 points)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

b. Based on the results of part a., are the effects of no physician visit measured by relative risks and attributable risks homogeneous by presence of co-morbidity? Why or why not? (1 point)

 

 

 

 

 

 

 

 

c. In order to estimate the independent effects, complete the re-constructed table below using the group of “No Co-morbidity” & “One or more First Trimester Physician Visit” as the reference group for each of the other three groups. (2 points)

 

 

 

 

Co-morbidity Present

 

Physician Visit First Trimester

 

Low BW

 

Normal BW

 

Incidence

 

(%)

 

RR

 

AR

 

No

 

One or more

 

 

 

 

 

 

 

 

 

 

 

No

 

None

 

 

 

 

 

 

 

 

 

 

 

Yes

 

One or more

 

 

 

 

 

 

 

 

 

 

 

Yes

 

None