Validity and reliability of maternal recall of prescription drug use during pregnancy By Marian Bakker

1. Validity of maternal recall
of prescription drug use during pregnancy
Marleen van Gelder1
Iris van Rooij1, Hermien de Walle2,
Nel Roeleveld1, Marian Bakker2
1) Department of Epidemiology, Biostatistics and HTA
Radboud University Nijmegen Medical Centre
2) Eurocat Northern Netherlands, Department of Genetics,
University Medical Center Groningen
EUROCAT 2011 symposium,
June 17 20 2011, Antwerp

2. Study design in birth defects epidemiology
• Majority of studies used case-control design
• Method of data collection:
 Medical records
 Self-administered questionnaire
 Interview
• Often data collection takes place months
to years after delivery
• Data on the accuracy of recall of prescription drug use during
pregnancy are scarce

3. Research questions
1. What is the validity of a self-administered questionnaire to
assess prescription drug use just before and during
pregnancy?
2. Do maternal and pregnancy characteristics influence the
accuracy of questionnaire data on prescription drug use
during pregnancy?

4. Methods (1): Study population
• Imbedded in Eurocat Northern Netherlands
 Population-based birth defects registry
 Covers provinces of Groningen, Friesland, and Drenthe
 Annually 18,000 births (10% of all births in Netherlands)
• Infants younger than 16 years and fetuses with birth defects
and genetic disorders eligible for registration
• Validation study: cases registered between 01-01-2009 and
30-06-2010 (n = 1,105)

5. Methods (2): Data collection
• Extensive questionnaire sent to parents
• Separate questionnaire on prescription drug use
 Screening question: “Did you use any…”
 Questions on specific indications / drug groups
o Specify drug in open-ended question
o Timing of use
• Pharmacy records checked for compliance
by maternal interviews

6. Methods (3): Statistical analyses
• Drugs ordered in three mutually exclusive categories:*
 For chronic conditions
 For occasional and short-term use
 Pregnancy-related
• “Gold Standard”: Eurocat database (pharmacy records)
• Validity: sensitivity and specificity
• Only drugs with ≥10 true exposures
• Multivariable logistic regression analysis for
selected maternal and pregnancy characteristics
*Bakker et al. BJOG 2006

7. Results (1): Descriptives
• Response rate questionnaire 72% (n=777)
• 560 women were included
 Pharmacy records not available for 55 women (8%)
 Gold Standard not yet available for 162 women (21%)
• Prescription drug use:
 Questionnaire:
o 233 women (42%)
o 129 different individual drugs / drug groups
 Gold Standard:
o 389 women (69%)
o 221 different individual drugs / drug groups

8. Results (1): Descriptives
• Response rate questionnaire 72% (n=777)
• 560 women were included
 Pharmacy records not available for 55 women (8%)
 Gold Standard not yet available for 162 women (21%)
• Prescription drug use:
 Questionnaire:
o 233 women (42%) Sensitivity: 59%
o 129 different individual drugs / drug groups
 Gold Standard:
o 389 women (69%)
o 221 different individual drugs / drug groups

9. Results (2): Validity and reliability comparisons
• Sensitivity drug categories:
 Corticosteroids: 12% (systemic corticosteroids: 50%)
 Antihypertensives / thyroid therapy: 88%
• Sensitivity individual drugs:
 Naproxen: 0%
 Salbutamol: 73%
• Specificity: 93-100%
• Sensitivity highest for chronic drugs
• Sensitivity first 4 months pregnancy generally comparable or
slightly better than for complete pregnancy period

10. Results (3): Characteristics influencing disagreement
• Most maternal and pregnancy characteristics did not
influence level of disagreement
• Disagreement occurred more often among:
 Younger women (<25 years of age)
 Women who had fertility problems
 Women who smoked during pregnancy
 Women who had miscarriage / stillbirth
 Women who completed questionnaire
>1 year after delivery

11. Discussion
• Strengths and limitations:
+ Choice of gold standard
+ High consent rate to obtain pharmacy records
– only mothers of infants with major birth defects
– no information on OTC drugs, low prevalence individual drugs
– screening question
• Validity comparable with studies conducted in the ‘80s and ‘90s
• Use of infants with genetic disorder as control group does not
seem to introduce recall bias

12. Conclusion
• Validity of self-administered questionnaire on prescription drug
use was generally moderate to poor for most drugs
• Future retrospective studies need additional data sources for
prescription drug use
• Drug-specific questions could increase sensitivity
• Data collection should be completed before or as shortly after
delivery as possible

13. Questions?
Thank you for your attention!