Bias	Author's judgment
Representativeness of the exposed cohort	Somewhat representative of the average population of pregnant women in the community*
Selection of the nonexposed cohort	Drawn from the same community as the exposed cohort*
Ascertainment of exposure	secure record (eg surgical records)*
Demonstration that outcome of interest was not present at start of study	Yes*
Comparability of cohorts based on the design or analysis	Does not control
Assessment of outcome	No description
Was follow‐up long enough for outcomes to occur	Yes*
Adequacy of follow up of cohorts	Complete follow up—all subjects accounted for*