Abstract
Objectives This study examines the extent of selection biases identified in the process of linking Medicaid claims with evidence of pregnancy to vital records. Methods Two years of Medicaid claims were scanned to identify pregnancy-related diagnoses and procedures. Information on 55,764 Medicaid recipients was provided to the Division of Health Statistics, which linked the information to vital records data on a range of identifying characteristics. Claims were then clustered by date and then into episodes of care surrounding the birth date of the infant. We identified 38,222 pregnancy episodes matched to vital records; 8,474 episodes unmatched to vital records that appeared to terminate before a delivery; and 5,278 episodes that appeared to include a delivery but did not match to vital records. The characteristics of matched episodes and unmatched episodes and the characteristics of matched episodes with and without delivery claims are compared. Results Unmatched episodes spanned fewer weeks than matched episodes, included more diagnostic indicators of elevated risk, and occurred more frequently in more impoverished populations. Among the matched records, 13% did not include claims for delivery services. These episodes occurred more frequently among Hispanic women, women delivering out of hospitals and women with preterm births and infant deaths. Conclusions The results provide evidence, as other studies have demonstrated, that matching Medicaid claims and vital records data is feasible. However, the matched analytic data set does tend to under-represent the outcomes of high-risk pregnancies. An additional source of selection bias can be avoided by using evidence of pregnancy as the Medicaid index for matching against vital records, rather than using only index cases with evidence of delivery.
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Acknowledgements
This work was made possible by the support and cooperation of the Arkansas Division of Medical Assistance, by Judith McGhee, M.D., M.P.H., Medical Director, DMA, The Arkansas Department of Public Health, and by the ANGELS Program, University of Arkansas for Medical Sciences.
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Appendix
Flag used in analysis | Condition | ICD9 CM Diagnostic codes on Medicaid claims used to identify occurrence |
|---|---|---|
Fetal demise (identifying incomplete pregnancy) | Fetal demise, ectopic pregnancy, spontaneous abortion, papyraceous fetus, intrauterine death | 632, 633, 634, 646.0–646.03, 656.4 |
Labor and delivery complications (absence suggests incomplete pregnancy) | Malposition, disproportion, pelvic abnormality, fetal distress, complications during labor and delivery, obstructed, abnormal or long labor, umbilical cord complications, obstetrical trauma, postpartum complications | 652, 653, 654, 655.7, 656.3, 659, 660,661,662, 663,664,665, 666–674 |
High-risk obstetrics history | Prior history of: early or threatened labor, fetal abnormality, fetal or neonatal death, preterm or low birth weight infant, uterine malformation | V23.4 or V23.5 with: 644, 655 or 740–759, 779.9, 656.4 or 658, 765 or 656.5 |
High-risk current pregnancy | Incompetent cervix, rubella, pre-eclampsia, suspected fetal abnormality, habitual aborter, hydramnios, hyperemesis beyond first trimester, gestation >3, conjoined twins, oligohydramnios, PROM before 34 weeks, deep phlebothrombosis | 654.5, 056 or 647.5, 642.5–642.7, 655.0–655.63 or 655.8–655.93, 646.3, 657, 643, 651.1,−651.2 or 651.4–9, 653.7, 658.0, 658.1–658.3, 671.3 |
High-risk pregnancy due to medical conditions | Severe asthma, cardiac disease, diabetes, epilepsy, hemoglobinapathy, hypertension, prior pulmonary embolism, pulmonary disease, chronic renal disease, coagulation defects, severe systemic disease, connective tissue disease, hemorrhagic conditions, history of cranial injury, cervical cancer, HIV, syphilis | 493, 390–399 or 410 or 414–414.9 or 416–417 or 424.0–425.9 or 648.6 or 426.0–427.9 or 428.0–429.9, 250, 250.1–250.9, 345 or 780.39, 282.60–282.69 or 282.0–282.5 or 282.7–285.9, 401–405.9 or 642.0–642.2, V23.4 and 671.2, 671.3, or 673, 136.3 or 415–417 or 492 or V46.1 or 496 or 500–519.9 or 494 or 010–018 or 647.3 or 481–486, 582–588.9 or 592 or 646.2, 286, 242–244.9 or 648.1 or 695.4 or 710.0 or 038 or 575.0–575.9 or 577.0–577.1 or 288.8–288.9 or 571.4 or 647.4 or 646.7 or 174, 759.82, 287, 430–434 or 437.0–437.6, 233.1, 180–184 or 622.1, 042 or V08, 090.0–097.9 or 647.0 |
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Bronstein, J.M., Lomatsch, C.T., Fletcher, D. et al. Issues and Biases in Matching Medicaid Pregnancy Episodes to Vital Records Data: The Arkansas Experience. Matern Child Health J 13, 250–259 (2009). https://doi.org/10.1007/s10995-008-0347-z
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DOI: https://doi.org/10.1007/s10995-008-0347-z