Anne Broe

Background: Counseling women who are either pregnant or contemplating pregnancy on their use of prescribed drugs remains a major clinical challenge. Since the thalidomide tragedy in the 1960s, the use of drugs during pregnancy has been subject to widespread concern due to the potential for unwanted effects on the unborn child, notably major congenital malformations. Objective: To examine the risk of major congenital malformations following first trimester exposure to all marketed prescription drugs in Denmark. Study Design: This was a population‐based cohort study utilizing national health registries in Denmark. We studied all singleton livebirths in Denmark between January 1, 2004, and December 31, 2017, and we linked data from the National Danish Prescription Register, Birth Register, Patient Register, and Cause of Death Register. Using logistic regression analysis, we compared exposed liveborn to unexposed liveborn children while controlling for important confounders. The main outcome measure was major congenital malformations, and the secondary outcomes included organ‐specific major congenital malformations as defined by EUROCAT. Results: Of 326 drugs with at least 5 livebirths with major congenital malformations, 31 were associated with an increased risk of major congenital malformations compared to unexposed livebirths (adjusted Odds Ratio [aOR] ≥ 2.0). Compared to livebirths of women who discontinued treatment prior to pregnancy, 17 drugs with an increased risk (aOR ≥ 2.0) were identified. Among 115 drugs prescribed to ≥ 1000 women during the first trimester, only insulins had aORs ≥ 2.0 for overall major congenital malformations. There were > 100 drugs with no increased risk of major congenital malformations. Conclusions: Using a complete nationwide dataset, > 100 null‐associations between first‐trimester drug exposure and overall major congenital malformations were documented. This provides important insights and reassurance to support pregnant women and inform shared decision making. We confirm previously known teratogenic drugs and other potential teratogenic drugs, clopidogrel and liraglutide, were identified. These latter associations should be addressed in future studies using disease‐specific confounder control.

Purpose: This study aimed to systematically evaluate the validity of variables related to pregnancy, delivery, and key characteristics of the infant in the Danish National Patient Register using maternal medical records as the reference standard. Patients and Methods: We reviewed medical records of 1264 women giving birth in the Region of Southern Denmark during 2017. We calculated positive (PPV) and negative (NPV) predictive values, sensitivity, and specificity to estimate the validity of 49 selected variables. Results: The PPV was ≥ 0.90 on most pregnancy-related variables including parity, pre-gestational BMI, diabetes disorders, and previous cesarean section, while it was lower for hypertensive disorders, especially mild to moderate preeclampsia (0.49, 95% CI 0.32– 0.66). Sensitivity ranged from 0.80 to 1.00 on all pregnancy-related variables, except hypertensive disorders (sensitivity 0.38– 0.71, lowest for severe preeclampsia). On most delivery-related variables including obstetric surgical procedures (eg cesarean section and induction of labor), pharmacological pain-relief, and gestational age at delivery, PPV’s ranged from 0.98 to 1.00 and the corresponding sensitivities from 0.87 to 1.00. Regarding infant-related variables, both the APGAR score registered five minutes after delivery and birthweight yielded a PPV of 1.00. Conclusion: Obstetric coding in the Danish National Patient Register shows very high validity and completeness making it a valuable source for epidemiologic research. Plain Language Summary: Danish register data are often used for epidemiological research in reproduction. The registers are based on coded information to the registers based on information from medical records. The quality of the register data is highly dependent of the validity of the codes. Yet there is a lack in our knowledge of the validity of data related to pregnancy, childbirth, and the characteristics of the newborn baby. We therefore aimed to validate the Danish National Patient Registry data related to pregnancy and childbirth by comparing the registered code with information from the medical records. We scrutinized medical records from 1264 women giving birth in the Region of Southern Denmark during 2017. We compared the registration in the medical record with the registered code in the Danish National Patient Registry by calculating how accurate the register data are according to 49 different variables. Results showed that registered codes in the Patient Registry for pregnancy- and childbirth-related conditions and key infant characteristics were to a high degree in agreement with the data from the medical report with few exceptions. In conclusion, the study revealed that the Danish National Patient Register provides highly accurate and comprehensive data for most pregnancy, delivery, and infant-related variables. This underscores the register’s value as a reliable source for epidemiologic research in reproductive health.

Letter to the Editor Pharmacoepidemiology and Drug SafetyAuthors: Christopher Lee1, Silvia Rizzi 1, Ana Luiza Bierrenbach1, Luis Antunes1, Niina-Maria Nissinen1, Olga Rocha1, Jennifer Campbell2, Caroline Minassian3, Susan Hodgson2, Anne Broe1

Purpose: To develop the Nordic Multimorbidity Index (NMI), a multimorbidity measure specifically suited to the Nordic health and administrative registry data based on current diagnosis, treatment, and coding practices. Methods: The NMI was developed to predict 5-year mortality in a population-based cohort of randomly sampled Danish residents aged ≥ 40 years (n = 425,087) followed from 2013 to 2018. Included predictors were selected from hospital diagnoses and filled drug prescriptions based on a combination of subject matter knowledge and a data-driven approach using backwards elimination. The performance of the NMI was assessed in a temporal validation cohort of Danish residents followed from 2007 to 2012 and in six cohorts of new users of selected drugs. The discriminative performance of the NMI, Charlson Comorbidity Index (CCI) and the Elixhauser Comorbidity Index (ECI) was assessed using the c-statistic from logistic regression models with 5-year mortality as dependent variable and the multimorbidity index score, age, and sex as independent variables. Results: The NMI included 50 predictors. In the temporal validation cohort, the c-statistic of the NMI (0.887, 95% CI 0.883– 0.890) exceeded that of the CCI (0.871, 95% CI 0.868– 0.874) and ECI (0.866, 95% CI 0.863– 0.870). In all new user cohorts, the NMI outperformed the other indices with c-statistics ranging from 0.781 (95% CI 0.779– 0.784) to 0.838 (95% CI 0.834– 0.842). Conclusion: The NMI predicted 5-year mortality in a general Danish population and six cohorts of new users of selected drugs and was superior to the CCI and ECI. The NMI could be preferred over these indices to quantify the level of multimorbidity for, eg, descriptive purposes or confounding control. The NMI should be validated in other patient populations and other Nordic countries.

International Journal of Epidemiology, dyab219, https://doi.org/10.1093/ije/dyab219 Published online: 13 October 2021