Comparison of recorded medication use in the Medical Birth Registry of Norway with prescribed medicines registered in the Norwegian Prescription Database

Determining antenatal medicine exposures in South African women: a comparison of three methods of ascertainment

BACKGROUND

In the absence of clinical trials, data on the safety of medicine exposures in pregnancy are dependent on observational studies conducted after the agent has been licensed for use. This requires an accurate history of antenatal medicine use to determine potential risks. Medication use is commonly determined by self-report, clinician records, and electronic pharmacy data; different data sources may be more informative for different types of medication and resources may differ by setting. We compared three methods to determine antenatal medicine use (self-report, clinician records and electronic pharmacy dispensing records [EDR]) in women attending antenatal care at a primary care facility in Cape Town, South Africa in a setting with high HIV prevalence.

METHODS

Structured, interview-administered questionnaires recorded self-reported medicine use. Data were collected from clinician records and EDR on the same participants. We determined agreement between these data sources using Cohen's kappa and, lacking a gold standard, used Latent Class Analysis to estimate sensitivity, specificity and positive predictive value (PPV) for each data source.

RESULTS

Between 55% and 89% of 967 women had any medicine use documented depending on the data source (median number of medicines/participant = 5 [IQR 3-6]). Agreement between the datasets was poor regardless of class except for antiretroviral therapy (ART; kappa 0.6-0.71). Overall, agreement was better between the EDR and self-report than with either dataset and the clinician records. Sensitivity and PPV were higher for self-report and the EDR and were similar for the two. Self-report was the best source for over-the-counter, traditional and complementary medicines; clinician records for vaccines and supplements; and EDR for chronic medicines.

CONCLUSIONS

Medicine use in pregnancy was common and no single data source included all the medicines used. ART was the most consistently reported across all three datasets but otherwise agreement between them was poor and dependent on class. Using a single data collection method will under-estimate medicine use in pregnancy and the choice of data source should be guided by the class of the agents being investigated.

Polypharmacy and comorbidities during pregnancy in a cohort of women with migraine

OBJECTIVE

To describe longitudinal patterns of medication use throughout pregnancy in women with migraine.

METHODS

We used the IBM MarketScan healthcare claims database in the US to create a cohort of pregnancies enrolled between 2011-2015 resulting in live or stillbirth. Migraine headache was identified based on ICD-9-CM diagnosis codes or procedure codes recorded in clinical encounters. Outcomes were patterns of prescriptions filled for medications that may be used to prevent migraine (antiepileptics, antihypertensives, antidepressants) or treat acute episodes (opioids, triptans, acetaminophen) and of other comorbid conditions (hypertension, psychiatric diagnoses, epilepsy). We used group-based multi-trajectory models to cluster women into similar longitudinal patterns of prescription fills.

RESULTS

Of 859,501 pregnancies, 8168 had migraine. Within migraineurs, before pregnancy, the most commonly filled prescription was for a triptan (43.2%), followed by opioids (26.7%), acetaminophen (26.2%), antidepressants (24.9%), antiepileptics (18.6%) and antihypertensives (12.3%). Antiepileptics, antidepressants, and triptans were frequently discontinued early in pregnancy with few new users, while antihypertensives were discontinued by some users, but continued or initiated by a minority of users late in pregnancy. Opioids and acetaminophen were used intermittently throughout pregnancy. Comorbidities included hypertension (10.8%), epilepsy (4.7%), depression (14.0%), and anxiety (15.6%). Polypharmacy involving both preventive and acute medications was most common before pregnancy (31.4%) and declined in first trimester (14.7%). In all, 25.9% of women filled prescriptions for two or more acute medications before pregnancy.

CONCLUSIONS

Medication use patterns during pregnancy for women with migraine are complex. Patterns of polypharmacy and comorbidity during pregnancy highlight an under-studied area relevant for maternal and child health outcomes.

Agreement Between Maternal Report and Medical Records During Pregnancy: Medications for Rheumatoid Arthritis and Asthma

BACKGROUND

There are limited data regarding the comparability of medication exposure information during pregnancy from maternal report and medical records, including for rheumatoid arthritis and asthma-related medications.

METHODS

This study included pregnant women with rheumatoid arthritis (n = 216) and asthma (n = 172) enrolled in the MothertoBaby Pregnancy Studies (2009-2014). Women reported types and dates of medications used through semi-structured telephone interviews up to three times during pregnancy and once after delivery, and medical records were obtained. We calculated Cohen's kappa coefficients and 95% confidence intervals (CIs) and per cent agreement for agreement between report and records.

RESULTS

For rheumatoid arthritis, prednisone was reported most frequently (53%). During pregnancy, kappa coefficients for rheumatoid arthritis medications ranged from 0.32 (95% CI 0.15, 0.50) for ibuprofen, with 84.3% agreement, to 0.90 (95% CI 0.84, 0.96) for etanercept with 95.4% agreement, and was 0.44 (95% CI 0.33, 0.55) for prednisone, with 71.3% agreement. For asthma, albuterol was reported most frequently (77.9%). During pregnancy, kappa coefficients for asthma medications ranged from 0.21 (95% CI 0.08, 0.35), with 64.5% agreement for albuterol to 0.84 (95% CI 0.71, 0.96) for budesonide/formoterol, with 96.5% agreement. Where kappas for any use during pregnancy were less than excellent (i.e. ≤0.80), medication use was more frequently captured by report than record.

CONCLUSIONS

Agreement was higher for medications typically used continuously than sporadically. Information on medication use from medical records alone may not be adequate when studying the impact of intermittently used medications during pregnancy on perinatal outcomes.

The limitations of some European healthcare databases for monitoring the effectiveness of pregnancy prevention programmes as risk minimisation measures

PURPOSE

Pregnancy prevention programmes (PPPs) exist for some medicines known to be highly teratogenic. It is increasingly recognised that the impact of these risk minimisation measures requires periodic evaluation. This study aimed to assess the extent to which some of the data needed to monitor the effectiveness of PPPs may be present in European healthcare databases.

METHODS

An inventory was completed for databases contributing to EUROmediCAT capturing pregnancy and prescription data in Denmark, Norway, the Netherlands, Italy (Tuscany/Emilia Romagna), Wales and the rest of the UK, to determine the extent of data collected that could be used to evaluate the impact of PPPs.

RESULTS

Data availability varied between databases. All databases could be used to identify the frequency and duration of prescriptions to women of childbearing age from primary care, but there were specific issues with availability of data from secondary care and private care. To estimate the frequency of exposed pregnancies, all databases could be linked to pregnancy data, but the accuracy of timing of the start of pregnancy was variable, and data on pregnancies ending in induced abortions were often not available. Data availability on contraception to estimate compliance with contraception requirements was variable and no data were available on pregnancy tests.

CONCLUSION

Current electronic healthcare databases do not contain all the data necessary to fully monitor the effectiveness of PPP implementation, and thus, special data collection measures need to be instituted.

Agreement and validity of electronic health record prescribing data relative to pharmacy claims data: A validation study from a US electronic health record database

BACKGROUND

Granular clinical and laboratory data available in electronic health record (EHR) databases provide researchers the opportunity to conduct investigations that would not be possible in insurance claims databases; however, for pharmacoepidemiology studies, accurate classification of medication exposure is critical.

OBJECTIVE

The aim of this study was to evaluate the validity of classifying medication exposure using EHR prescribing (EHR-Rx) data.

METHODS

We conducted a retrospective cohort study among patients with linked claims and EHR data in OptumLabs™ Data Warehouse. The agreement between EHR-Rx data and pharmacy claims (PC-Rx) data (for 40 medications) was determined using the positive predictive value (PPV) and medication possession ratio (MPR)-calculated in 1- and 12-month medication exposure periods (MEPs). Secondary analyses were restricted to incident vs prevalent EHR-Rxs, age ≥65 vs <65, white vs black race, males vs females, and number of EHR-Rxs.

RESULTS

The validity metrics varied substantially among the 40 medications assessed. Across all medications, the period PPV and MPR were 62% and 63% in the 1-month MEP. They were 78% and 43% in the 12-month MEP. Overall, PPV and MPR were higher for patients with a prevalent EHR-Rx and age <65.

CONCLUSIONS

Despite substantial variability among different medications, there was very good agreement between EHR-Rx data and PC-Rx data. To maximize the validity of classifying medication exposure with EHR prescribing data, researchers may consider using longer MEPs (eg, 12 months) and potentially require multiple EHR-Rxs to classify baseline medication exposure.

Improving Information on Maternal Medication Use by Linking Prescription Data to Congenital Anomaly Registers: A EUROmediCAT Study

Introduction

Research on associations between medication use during pregnancy and congenital anomalies is significative for assessing the safe use of a medicine in pregnancy. Congenital anomaly (CA) registries do not have optimal information on medicine exposure, in contrast to prescription databases. Linkage of prescription databases to the CA registries is a potentially effective method of obtaining accurate information on medicine use in pregnancies and the risk of congenital anomalies.

Methods

We linked data from primary care and prescription databases to five European Surveillance of Congenital Anomalies (EUROCAT) CA registries. The linkage was evaluated by looking at linkage rate, characteristics of linked and non-linked cases, first trimester exposure rates for six groups of medicines according to the prescription data and information on medication use registered in the CA databases, and agreement of exposure.

Results

Of the 52,619 cases registered in the CA databases, 26,552 could be linked. The linkage rate varied between registries over time and by type of birth. The first trimester exposure rates and the agreements between the databases varied for the different medicine groups. Information on anti-epileptic drugs and insulins and analogue medicine use recorded by CA registries was of good quality. For selective serotonin reuptake inhibitors, anti-asthmatics, antibacterials for systemic use, and gonadotropins and other ovulation stimulants, the recorded information was less complete.

Conclusion

Linkage of primary care or prescription databases to CA registries improved the quality of information on maternal use of medicines in pregnancy, especially for medicine groups that are less fully registered in CA registries.

Prescribing of Antidiabetic Medicines before, during and after Pregnancy: A Study in Seven European Regions

AIM

To explore antidiabetic medicine prescribing to women before, during and after pregnancy in different regions of Europe.

METHODS

A common protocol was implemented across seven databases in Denmark, Norway, The Netherlands, Italy (Emilia Romagna/Tuscany), Wales and the rest of the UK. Women with a pregnancy starting and ending between 2004 and 2010, (Denmark, 2004-2009; Norway, 2005-2010; Emilia Romagna, 2008-2010), which ended in a live or stillbirth, were identified. Prescriptions for antidiabetic medicines issued (UK) or dispensed (non-UK) during pregnancy and/or the year before or year after pregnancy were identified. Prescribing patterns were compared across databases and over calendar time.

RESULTS

1,082,673 live/stillbirths were identified. Pregestational insulin prescribing during the year before pregnancy ranged from 0.27% (CI95 0.25-0.30) in Tuscany to 0.45% (CI95 0.43-0.47) in Norway, and increased between 2004 and 2009 in all countries. During pregnancy, insulin prescribing peaked during the third trimester and increased over time; third trimester prescribing was highest in Tuscany (2.2%) and lowest in Denmark (0.5%). Of those prescribed an insulin during pregnancy, between 50.5% in Denmark and 88.8% in the Netherlands received an insulin analogue alone or in combination with human insulin, this proportion increasing over time. Oral products were mainly metformin and prescribing was highest in the 3 months before pregnancy. Metformin use during pregnancy increased in some countries.

CONCLUSION

Pregestational diabetes is increasing in many areas of Europe. There is considerable variation between and within countries in the choice of medication for treating pregestational diabetes in pregnancy, including choice of insulin analogues and oral antidiabetics, and very large variation in the treatment of gestational diabetes despite international guidelines.

Prevalence of prescription medication use among non-pregnant women of childbearing age and pregnant women in the United States: NHANES, 1999-2006

Many prescription medications have limited information regarding safety for use during pregnancy. In order to inform research on safer medication use during pregnancy, we examined prescription medication use among women in the United States. We analyzed data from the 1999-2006 National Health and Nutrition Examination Survey (NHANES) to estimate the prevalence of prescription medication use in the past 30 days among pregnant women and non-pregnant women of childbearing age (15-44 years) and to ascertain the most commonly reported prescription medications by women in these groups. We assessed how the most commonly reported medications differed among groups defined by selected demographic characteristics, including age, race/ethnicity, and markers of socioeconomic status. Prescription medication use in the past 30 days was reported by 22 % of pregnant women and 47 % of non-pregnant women of childbearing age. The most commonly reported prescription medications by NHANES participants differed somewhat by pregnancy status; allergy and anti-infective medications were more common among pregnant women, while oral contraceptives were more common among non-pregnant women. Use of prescription medication for asthma and thyroid disorders was reported by both groups. Although prescription medication use in the previous 30 days was less common among pregnant women than non-pregnant women, its use was reported among almost 1 in 4 pregnant women. Many of the most common medications reported were for the treatment of chronic medical conditions. Given the potential impact of medications on the developing fetus, our data underscore the importance of understanding the safety of these medications during pregnancy.

Asthma medication prescribing before, during and after pregnancy: a study in seven European regions

OBJECTIVES

To explore utilisation patterns of asthma medication before, during and after pregnancy as recorded in seven European population-based databases.

DESIGN

A descriptive drug utilisation study.

SETTING

7 electronic healthcare databases in Denmark, Norway, the Netherlands, Italy (Emilia Romagna and Tuscany), Wales, and the Clinical Practice Research Datalink representing the rest of the UK.

PARTICIPANTS

All women with a pregnancy ending in a delivery that started and ended between 2004 and 2010, who had been present in the database for the year before, throughout and the year following pregnancy.

MAIN OUTCOME MEASURES

The percentage of deliveries where the woman received an asthma medicine prescription, based on prescriptions issued (UK) or dispensed (non-UK), during the year before, throughout or during the year following pregnancy. Asthma medicine prescribing patterns were described for 3-month time periods and the choice of asthma medicine and changes in prescribing over the study period were evaluated in each database.

RESULTS

In total, 1,165,435 deliveries were identified. The prevalence of asthma medication prescribing during pregnancy was highest in the UK and Wales databases (9.4% (CI95 9.3% to 9.6%) and 9.4% (CI95 9.1% to 9.6%), respectively) and lowest in the Norwegian database (3.7% (CI95 3.7% to 3.8%)). In the year before pregnancy, the prevalence of asthma medication prescribing remained constant in all regions. Prescribing levels peaked during the second trimester of pregnancy and were at their lowest during the 3-month period following delivery. A decline was observed, in all regions except the UK, in the prescribing of long-acting β-2-agonists during pregnancy. During the 7-year study period, there were only small changes in prescribing patterns.

CONCLUSIONS

Differences were found in the prevalence of prescribing of asthma medications during and surrounding pregnancy in Europe. Inhaled β-2 agonists and inhaled corticosteroids were, however, the most popular therapeutic regimens in all databases.

Medication use during pregnancy, gestational age and date of delivery: agreement between maternal self-reports and health database information in a cohort

Background

Health databases are a promising resource for epidemiological studies on medications safety during pregnancy. The reliability of information on medications exposure and pregnancy timing is a key methodological issue. This study (a) compared maternal self-reports and database information on medication use, gestational age, date of delivery; (b) quantified the degree of agreement between sources; (c) assessed predictors of agreement.

Methods

Pregnant women recruited in a prenatal clinic in Friuli Venezia Giulia (FVG) region, Italy, from 2007 to 2009, completed a questionnaire inquiring on medication use during pregnancy, gestational age and date of delivery. Redeemed prescriptions and birth certificate records were extracted from regional databases through record linkage. Percent agreement, Kappa coefficient, prevalence and bias-adjusted Kappa (PABAK) were calculated. Odds Ratio (OR), with 95 % confidence interval (95 % CI), of ≥1 agreement was calculated through unconditional logistic regression.

Results

The cohort included 767 women, 39.8 % reported medication use, and 70.5 % were dispensed at least one medication. Kappa and PABAK indicated almost perfect to substantial agreement for antihypertensive medications (Kappa 0.86, PABAK 0.99), thyroid hormones (0.88, 0.98), antiepileptic medications (1.00, 1.00), antithrombotic agents (0.70, 0.96). PABAK value was greater than Kappa for medications such as insulin (Kappa 0.50, PABAK 0.99), antihistamines for systemic use (0.50, 0.99), progestogens (0.28, 0.79), and antibiotics (0.12, 0.63). Adjusted OR was 0.48 (95 % CI 0.26; 0.90) in ex- vs. never smokers, 0.64 (0.38; 1.08) in < high school vs. university, 1.55 (1.01; 2.37) in women with comorbidities, 2.25 (1.19; 4.26) in those aged 40+ vs. 30–34 years.

Gestational age matched exactly in 85.2 % and date of delivery in 99.5 %.

Conclusions

For selected medications used for chronic conditions, the agreement between self-reports and dispensing data was high. For medications with low to very low prevalence of use, PABAK provides a more reliable measure of agreement. Maternal reports and dispensing data are complementary to each other to increase the reliability of information on the use of medications during pregnancy. Birth certificates provide reliable data on the timing of pregnancy. FVG health databases are a valuable source of data for pregnancy research.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-015-0745-3) contains supplementary material, which is available to authorized users.

Antiepileptic drug prescribing before, during and after pregnancy: a study in seven European regions

PURPOSE

The aim of this study was to explore antiepileptic drug (AED) prescribing before, during and after pregnancy as recorded in seven population-based electronic healthcare databases.

METHODS

Databases in Denmark, Norway, the Netherlands, Italy (Emilia Romagna/Tuscany), Wales and the Clinical Practice Research Datalink, representing the rest of the UK, were accessed for the study. Women with a pregnancy starting and ending between 2004 and 2010, which ended in a delivery, were identified. AED prescriptions issued (UK) or dispensed (non-UK) at any time during pregnancy and the 6 months before and after pregnancy were identified in each of the databases. AED prescribing patterns were analysed, and the choice of AEDs and co-prescribing of folic acid were evaluated.

RESULTS

In total, 978 957 women with 1 248 713 deliveries were identified. In all regions, AED prescribing declined during pregnancy and was lowest during the third trimester, before returning to pre-pregnancy levels by 6 months following delivery. For all deliveries, the prevalence of AED prescribing during pregnancy was 51 per 10 000 pregnancies (CI95 49-52%) and was lowest in the Netherlands (43/10 000; CI95 33-54%) and highest in Wales (60/10 000; CI95 54-66%). In Denmark, Norway and the two UK databases lamotrigine was the most commonly prescribed AED; whereas in the Italian and Dutch databases, carbamazepine, valproate and phenobarbital were most frequently prescribed. Few women prescribed with AEDs in the 3 months before pregnancy were co-prescribed with high-dose folic acid: ranging from 1.0% (CI95 0.3-1.8%) in Emilia Romagna to 33.5% (CI95 28.7-38.4%) in Wales.

CONCLUSION

The country's differences in prescribing patterns may suggest different use, knowledge or interpretation of the scientific evidence base. The low co-prescribing of folic acid indicates that more needs to be done to better inform clinicians and women of childbearing age taking AEDs about the need to offer and receive complete preconception care.

Drug exposure: inclusion of dispensed drugs before pregnancy may lead to underestimation of risk associations

OBJECTIVES

To assess the impact of exposure misclassification on risk associations when using prescription databases as the source for drug exposure in pregnancy by applying results from a validation analysis of exposure classification.

STUDY DESIGN AND SETTING

Linkage of data on 27,656 participants in the Norwegian Mother and Child Cohort Study (MoBa) with the Norwegian Prescription Database (NorPD). Exposure to selective serotonin reuptake inhibitors (SSRIs) was defined by dispensed drugs during pregnancy including different time windows before pregnancy. The validity of NorPD data was estimated using self-reported use in MoBa as the reference standard. We applied the results from the validation analysis on data from a Nordic study on SSRI use in pregnancy and risk of persistent pulmonary hypertension in the newborn.

RESULTS

Sensitivity increased and specificity decreased when the time window in NorPD was expanded before pregnancy. Using the same time window as in the Nordic study (+90 days before pregnancy), for use in early pregnancy, the odds ratio (OR) corrected for misclassification was 2.6 compared with the OR of 1.6 in the Nordic study.

CONCLUSION

Expansion of the time window to include intervals before pregnancy can lead to lower specificity and underestimation of risk associations.

The Nordic prescription databases as a resource for pharmacoepidemiological research--a literature review

PURPOSE

All five Nordic countries have nationwide prescription databases covering all dispensed drugs, with potential for linkage to outcomes. The aim of this review is to present an overview of therapeutic areas studied and methods applied in pharmacoepidemiologic studies using data from these databases.

METHODS

The study consists of a Medline-based structured literature review of scientific papers published during 2005-2010 using data from the prescription databases in Denmark, Finland, Iceland, Norway, and Sweden, covering 25 million inhabitants. Relevant studies were analyzed in terms of pharmacological group, study population, outcomes examined, type of study (drug utilization vs. effect of drug therapy), country of origin, and extent of cross-national collaboration.

RESULTS

A total of 515 studies were identified. Of these, 262 were conducted in Denmark, 97 in Finland, 4 in Iceland, 87 in Norway, and 61 in Sweden. Four studies used data from more than one Nordic country. The most commonly studied drugs were those acting on the nervous system, followed by cardiovascular drugs and gastrointestinal/endocrine drugs. A total of 228 studies examined drug utilization and 263 focused on the effects and safety of drug therapy. Pregnant women were the most commonly studied population in safety studies, whereas prescribers' adherence to guidelines was the most frequent topic of drug utilization studies.

CONCLUSIONS

The Nordic prescription databases, with their possibility of record-linkage, represent an outstanding resource for assessing the beneficial and adverse effects of drug use in large populations, under routine care conditions, and with the potential for long-term follow-up.

Periconceptional folic acid and teratogenic drug use in women undergoing fertility treatments

OBJECTIVE

To evaluate periconception drug use in women undergoing fertility treatment and compare it to women with spontaneous pregnancies.

METHODS

Retrospective observational cohort study on reproductive-age women. Data on pregnancies, fertility treatments, prescription fillings and demographics were extracted from Clalit Health Services computerized systems. Two quality measures were evaluated: periconception folic acid prescription fillings and use of potentially hazardous drugs in early pregnancy.

RESULTS

There were 12,891 fertility treatment cycles in 4868 women; and 4968 women had spontaneous pregnancy. Periconceptional folic acid use was low and similar in both groups (31.3% of fertility cycles versus 29.9% of spontaneous pregnancies, p = 0.07). In the infertility group, 293 prescriptions for potentially hazardous drugs were filled within 45 days after the beginning of a fertility cycle (2.3% of cycles) compared to only 47 (0.9%) in women with spontaneous pregnancy (p < 0.001).

CONCLUSIONS

The periconception medical care of women who undergo fertility treatment is suboptimal and is not better than in women with spontaneous pregnancies. Folic acid use that can reduce the risk of congenital anomalies is underused; whereas the use of potentially hazardous drugs in early pregnancy is significant. More intensive and targeted counseling regarding drug use before pregnancy is urgently needed.

Agreement between self-report and prescription data in medical records for pregnant women

BACKGROUND Clinical teratology studies often rely on patient reports of medication use in pregnancy with or without other sources of information. Electronic medical records (EMRs), administrative databases, pharmacy dispensing records, drug registries, and patients' self-reports are all widely used sources of information to assess potential teratogenic effect of medications. The objective of this study was to assess comparability of self-reported and prescription medication data in EMRs for the most common therapeutic classes. METHODS The study population included 404 pregnant women prospectively recruited from five prenatal care clinics affiliated with the University of New Mexico. Self-reported information on prescription medications taken since the last menstrual period (LMP) was obtained by semistructured interviews in either English or Spanish. For validation purposes, EMRs were reviewed to abstract information on medications prescribed between the LMP and the date of the interview. Agreement was estimated by calculating a kappa (κ) coefficient, sensitivity, and specificity. RESULTS In this sample of socially-disadvantaged (i.e., 67.9% high school education or less, 48.5% no health insurance), predominantly Latina (80.4%) pregnant women, antibiotics and antidiabetic agents were the most prevalent therapeutic classes. The agreement between the two sources substantially varied by therapeutic class, with the highest level of agreement seen among antidiabetic and thyroid medications (κ ≥0.8) and the lowest among opioid analgesics (κ = 0.35). CONCLUSIONS Results indicate a high concordance between self-report and prescription data for therapeutic classes used chronically, while poor agreement was observed for medications used intermittently, on an 'as needed" basis, or in short courses.

Antidepressant use during pregnancy: comparison of data obtained from a prescription register and from antenatal care records

PURPOSE

To compare interview data on drug use during pregnancy with data identified from a register of prescriptions.

MATERIALS

We compared information from the Swedish Prescribed Drug Register with the Swedish Medical Birth Register on antidepressant use. In order to evaluate the clinical significance of the difference in ascertainment with the two methods, the rate of preterm births among singletons and of neonatal symptoms were studied.

RESULTS

During the year before the last menstrual period, 1.5% of the women filled prescriptions for antidepressants each month. Already before the pregnancy was known, the rate of filled prescriptions decreased and reached 0.5% towards the end of the pregnancy. Twenty-two percent of first-trimester use of antidepressants was unidentified using interview data and prescriptions during the 2nd and 3rd pregnancy months covered only 55% of actual use. When women who filled prescriptions 1 or 3 months before the last menstrual period were included, 17 and 43% respectively of women were included who probably did not use the drugs in the first trimester. Prescriptions gave a more complete ascertainment of drug use after the first trimester than data from antenatal care, which seemed to overestimate drug use.

CONCLUSIONS

Interview data seem to give the most valid results on early use. When interview data are not available, prescription data could be used, but should not include prescriptions given earlier than 1 month before the last menstrual period. Studies of drug use later in pregnancy are best based on prescription data in the absence of interview data.