ABSTRACT
Aim: Pregnant women are hypothesized to have low adherence to
prescribed medication, because of concerns about toxicity and harmful
effects on the unborn child. However, very little is known about the
actual adherence to prescribed medication during pregnancy. We
determined to what extent women follow treatment recommendations
regarding prescribed medication use in mid-pregnancy.
Methods: Dutch women participating in the PRIDE Study completed
a six-week diary on medication use. Additionally, pharmacy records were
obtained. For each medication dispensed, we determined three measures of
adherence: 1) whether use was reported in the diary (actual use), 2)
difference between dispensing date and date of first reported use
(initiation time), and 3) proportion of days with at least the correct
number of doses taken (implementation adherence).
Results: During the six-weeks study period, 235 of 816 women
(29%) were prescribed medication. Actual use was highest for
medications used for chronic conditions (88%; 95% confidence interval
[95% CI] 81-93), followed by medication for pregnancy-related
conditions (79%; 95% CI 71-86) and medication for occasional and
short-time use (69%; 95% CI 60-77). We observed a ≥1 day delay in
treatment initiation for 42% of medications dispensed for the first
time in the study period. For medications that were actually used, mean
implementation adherence was 74.2% (95% CI 69.3-79.2).
Conclusion: Although actual use of medications dispensed was
high, many pregnant women did not adhere to treatment recommendations.
This non-adherence may impact maternal and child health and lead to
exposure misclassification in studies in perinatal pharmacoepidemiology
relying on administrative databases.