TABLE III.

Complementary strengths and weaknesses of the 3 study arms of VAMPSS

Characteristic	Strengths	Potential weaknesses
Study design
Cohort	• Prospective • Multiple outcomes	• Limited statistical power for specific birth defects • More costly
Case-control	• Multiple exposures • Statistical power for specific birth defects • Less costly	• Retrospective • Limited statistical power for infrequent exposures
Database	• Prospective • Population-based • Multiple exposures • Multiple outcomes • Statistical power for groups of defects possible • May be least costly
Medication exposure capture
Cohort	• Data captured on medication as actually taken • Data captured on OTC medications (including vitamins) • Data captured on borrowed medication
Case-control	• Data captured on medication as actually taken • Data captured on OTC medications (including vitamins) • Data captured on borrowed medication	• Retrospective exposure information
Database		• Medication prescribed may not be taken • Timing of exposure estimated when gestational age is not captured
Bias and confounding
Cohort	• Outcomes confirmed by interview and medical records • Data available on confounders, eg, alcohol, tobacco, and folic acid use	• Potential volunteer bias
Case-control	• Outcomes confirmed by interview and medical records • Data available on confounders, eg, alcohol, tobacco, and folic acid use	• Potential volunteer bias • Potential recall bias • Potential biased control selection
Database	• No selection bias • Diagnoses in pregnancy losses rarely captured	• Data not available for some key confounders, eg body mass index

OTC, Over-the-counter.