Preconception venous thromboembolism and placenta‐mediated pregnancy complications
2015; Elsevier BV; Volume: 13; Issue: 9 Linguagem: Inglês
10.1111/jth.13046
ISSN1538-7933
AutoresA.T. Hansen, Morten Schmidt, Erzsébet Horváth‐Puhó, Lars Pedersen, Kenneth J. Rothman, Anne‐Mette Hvas, Henrik Toft Sørensen,
Tópico(s)Maternal and fetal healthcare
ResumoJournal of Thrombosis and HaemostasisVolume 13, Issue 9 p. 1635-1641 Original ArticleFree Access Preconception venous thromboembolism and placenta-mediated pregnancy complications A. T. Hansen, Corresponding Author A. T. Hansen Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, Denmark Department of Clinical Biochemistry, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, Denmark Correspondence: Anette Tarp Hansen, Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, DK-8200 Aarhus N, Denmark. Tel.: +45 2274 2818; fax: +45 871 67215. E-mail: anette.tarp.hansen@dadlnet.dkSearch for more papers by this authorM. Schmidt, M. Schmidt Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, DenmarkSearch for more papers by this authorE. Horváth–Puhó, E. Horváth–Puhó Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, DenmarkSearch for more papers by this authorL. Pedersen, L. Pedersen Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, DenmarkSearch for more papers by this authorK. J. Rothman, K. J. Rothman Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, Denmark RTI Health Solutions, Research Triangle Institute, Research Triangle Park, NC, USASearch for more papers by this authorA. M. Hvas, A. M. Hvas Department of Clinical Biochemistry, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, DenmarkSearch for more papers by this authorH. T. Sørensen, H. T. Sørensen Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, DenmarkSearch for more papers by this author A. T. Hansen, Corresponding Author A. T. Hansen Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, Denmark Department of Clinical Biochemistry, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, Denmark Correspondence: Anette Tarp Hansen, Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, DK-8200 Aarhus N, Denmark. Tel.: +45 2274 2818; fax: +45 871 67215. E-mail: anette.tarp.hansen@dadlnet.dkSearch for more papers by this authorM. Schmidt, M. Schmidt Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, DenmarkSearch for more papers by this authorE. Horváth–Puhó, E. Horváth–Puhó Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, DenmarkSearch for more papers by this authorL. Pedersen, L. Pedersen Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, DenmarkSearch for more papers by this authorK. J. Rothman, K. J. Rothman Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, Denmark RTI Health Solutions, Research Triangle Institute, Research Triangle Park, NC, USASearch for more papers by this authorA. M. Hvas, A. M. Hvas Department of Clinical Biochemistry, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, DenmarkSearch for more papers by this authorH. T. Sørensen, H. T. Sørensen Department of Clinical Epidemiology, Center for Haemophilia and Thrombosis, Aarhus University Hospital, Aarhus, DenmarkSearch for more papers by this author First published: 14 July 2015 https://doi.org/10.1111/jth.13046Citations: 12 Manuscript handled by: F. R. Rosendaal Final decision: F. R. Rosendaal, 19 June 2015 AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Summary Background Placenta-mediated complications are leading causes of maternal and fetal morbidity and mortality. We hypothesized that a preconception history of venous thromboembolism (VTE) is associated with increased risk of placenta-mediated pregnancy complications. Methods A nationwide population-based cohort study of all singleton pregnancies leading to delivery from 1997 to 2012 (n = 964 967). We obtained data on placenta-mediated pregnancy complications from the Danish Medical Birth Registry and data on VTE before pregnancy from the Danish National Patient Registry. We computed absolute risks, crude and adjusted risk differences (RDs) using a binomial regression model, and crude and adjusted risk ratios (RRs) from a modified Poisson regression model. Results Overall, 1419 women had a preconception history of VTE, while 578 112 did not. Preeclampsia occurred in 4.2% of pregnancies in the VTE group and in 2.7% of pregnancies in a comparison cohort (adjusted RD = 1.3%, 95% confidence interval (CI) 0.6–2.0%; adjusted RR = 1.5, 95% CI 1.3–1.8). Stillbirth occurred in 0.7% of pregnancies in the VTE group and in 0.4% of pregnancies in the comparison cohort (adjusted RD = 0.3%, 95% CI 0.02–0.6%; adjusted RR = 1.8, 95% CI 1.1–3.0). Placental abruption occurred in 0.8% of pregnancies in the VTE group and in 0.5% of pregnancies in the comparison cohort (adjusted RD = 0.3%, 95% CI − 0.05–0.6%; adjusted RR = 1.6, 95% CI 1.1–2.4). Small-for-gestational-age infants accounted for 10.9% of live births in the VTE group and 9.8% of live births in the comparison cohort (adjusted RD = 0.6%, 95% CI − 0.5–1.7%; adjusted RR = 1.1, 95% CI 0.9–1.3). Conclusion Women with a history of VTE were at increased risk of placenta-mediated complications. Introduction Maternal death during pregnancy is a major health concern worldwide. Placenta-mediated pregnancy complications (preeclampsia, stillbirth, birth of a small-for-gestational-age infant and placental abruption) are leading causes of both maternal and fetal/infant deaths 1-5. These deaths may be prevented by identifying women at risk of such placenta-mediated pregnancy complications. Venous thromboembolism (VTE) and placenta-mediated pregnancy complications may have a shared etiology. Women with previous preeclampsia are at increased risk of both recurrent placenta-mediated pregnancy complications and VTE in subsequent pregnancies 1, 2, 5, 6. However, it has not yet been confirmed that a preconception history of VTE predicts placenta-mediated pregnancy complications in subsequent pregnancies. Studies examining this hypothesis have had conflicting results and have been limited by lack of a clear comparison between women with and without a preconception history of VTE 7, 8. We therefore conducted a nationwide cohort study in Denmark to examine the extent to which a preconception history of VTE was associated with risk of placenta-mediated pregnancy complications. Methods Setting The Danish healthcare system is tax supported and ensures free access to healthcare services. All inhabitants of Denmark are given a unique Civil Personal Register number at birth or upon immigration, enabling linkage between Danish registries at the individual level 9. Data sources We obtained data from the Medical Birth Registry (MBR), the Danish National Patient Registry (DNPR) and the Danish Civil Registration System 9-11. The MBR contains data prospectively collected since 1 January 1973 by the midwives and doctors attending all births in Denmark 10. This registry includes data on maternal age, parity, gestational age at birth, birth weight and length of the neonate, and personal identifiers for both mother and child. Information on self-reported smoking status has been available in the registry since 1991 and information on maternal pre-pregnancy body mass index (BMI) has been available since 2004. The DNPR contains data on all admissions and discharges from Danish hospitals since 1977 and from emergency room and outpatient clinic visits since 1995 11. Each hospital inpatient discharge and hospital outpatient visit is recorded in the registry with one primary diagnosis and an optional number of secondary diagnoses classified according to the International Classification of Diseases, 8th revision (ICD-8) until the end of 1993 and the 10th revision (ICD-10) thereafter 11. Study population We included all singleton pregnancies leading to delivery in Denmark from 1997 to 2012. Figure 1 shows the inclusion and exclusion criteria for the study population. Figure 1Open in figure viewerPowerPoint Flow chart of inclusions and exclusions for the study population. Preconception VTE We obtained information on preconception history of VTE for each pregnancy leading to a delivery, using hospital inpatient and outpatient primary and secondary diagnoses in the DNPR since 1977 11. We restricted history of VTE to deep venous thrombosis (DVT) and pulmonary embolism (PE). Women with a preconception history of VTE were identified by the date of their first outpatient visit for clinic-based VTE treatment or by their discharge date for a VTE-related hospitalization 12. Emergency room diagnoses, which are working diagnoses, were not considered due to their low positive predictive values 13. Associated registry codes are provided in Table S1. Each pregnancy was considered an independent observation, for which preconception history of VTE and comorbidity status were determined separately from a woman's other pregnancies. Thus, women experiencing a VTE after a delivery were considered unexposed during the associated pregnancy, but exposed in subsequent pregnancies. We subcategorized VTE as provoked when a diagnosis of cancer was made before or within 90 days after the diagnosis of VTE or if a fracture or surgery occurred within 90 days before the diagnosis of VTE 14. The remaining VTEs were classified as unprovoked 14. If more than one VTE was recorded before pregnancy and if at least one of these was unprovoked, VTE status was classified as unprovoked. Other risk factors Using all available primary and secondary diagnoses recorded in the DNPR before the conception date, we also obtained information on other medical conditions known to increase the risk of pregnancy complications; that is, diabetes, essential hypertension and chronic renal disease. Placenta-mediated pregnancy complications The conception date was defined as the date of birth minus gestational age at delivery (in days) plus 14 days. It was possible to employ this algorithm because data are recorded in the MBR starting on the first day of the last menstrual period 10. Follow-up time was defined as the interval starting at gestational week 22 (thereby excluding aborted pregnancies) and ending at delivery. We defined a small-for-gestational-age infant as having a birth weight below the 10th percentile for all live-born infants for a given gestational week 15, 16. We derived the centile values from our own analysis dataset, calculating the 10th percentile for each completed gestational week separately for boys and girls. Preeclampsia was defined as proteinuria and hypertension after gestational week 20 (systolic/diastolic blood pressure above 140/90 mmHg, mild preeclampsia; diastolic blood pressure above 110 mmHg, severe preeclampsia) 17. Stillbirth was defined as fetal loss after gestational week 22 17. Statistical analysis We computed the absolute risk of each placenta-mediated pregnancy complication in women with and without a preconception history of VTE. We also computed crude and adjusted risk differences (RDs) using a binomial regression model with an identity link function, and crude and adjusted risk ratios (RRs) from a modified Poisson regression model 18-20. We controlled for maternal age, parity, maternal smoking, diabetes, essential hypertension and chronic renal disease in the model. For the subgroup of pregnancies occurring between 1 January 2005 and 31 December 2012, we also adjusted for pre-pregnancy BMI. We repeated the analyses separately for DVT, PE, provoked VTE and unprovoked VTE. To study potential effect-measure modification, we examined the adjusted RRs in strata of maternal age, parity and previous preeclampsia, and for deliveries during 2005–2012 in strata of maternal pre-pregnancy BMI. We repeated our analyses after excluding immigrants to minimize the risk of left-truncation of VTE history (N = 824 904 pregnancies). The study was approved by the Danish Data Protection Agency (#1-16-02-1-08). According to Danish law, ethical approval is not needed for studies that are entirely registry based. Results Characteristics We identified 579 531 women with a total of 964 967 pregnancies. Among these, 1419 women with 2757 pregnancies (0.3%) had a preconception diagnosis of VTE, while 578 112 did not. Among the VTE diagnoses, 2006 were DVTs and 751 were PEs (Table 1). Median maternal age at time of delivery was 31 years in the VTE group and 30 years in the comparison cohort. For deliveries recorded between 2005 and 2012, median pre-pregnancy maternal BMI was 24 kg m−2 in the VTE group and 23 kg m−2 in the comparison cohort. Table 1. Maternal characteristics for all pregnancies leading to delivery during 1997–2012 in Denmark according to preconception history of venous thromboembolism (VTE) No preconception VTE Preconception VTE Total n % n % n % Total pregnancies 962 210 100 2757 100 964 967 100 Total women 578 112 100 1419 100 579 531 100 Maternal age at delivery 12–29 years 450 839 46.9 1019 37.0 451 858 46.8 30–34 years 343 353 35.7 1067 38.7 344 420 35.7 35+ years 168 018 17.5 671 24.3 168 689 17.5 Maternal pre-pregnancy body mass index levelcc Information on pre-pregnancy body mass index (BMI) was obtained from the Medical Birth Registry for the years 2005–2012. Total 471 739 100 1699 100 473 438 100 < 25 kg m−2 298 241 63.2 882 51.9 299 123 63.2 25–29 kg m−2 94 137 20.0 392 23.1 94 529 20.0 30+ kg m−2 54 378 11.5 343 20.2 54 721 11.6 Parity 1 407 773 42.4 986 35.8 408 759 42.4 2 365 081 37.9 1094 39.7 366 175 37.9 3+ 189 356 19.7 677 24.6 190 033 19.7 Previous preeclampsia 18 957 2.0 92 3.3 19 049 2.0 Other risk factors Maternal smoking 166 508 17.3 561 20.3 167 069 17.3 Diabetes 4216 0.4 23 0.8 4239 0.4 Essential hypertension 4056 0.4 29 1.1 4085 0.4 Chronic renal disease 1718 0.2 22 0.8 1740 0.2 Fractureaa Discharge diagnosis of fracture or surgery within 90 days before the hospital inpatient admission or outpatient hospital clinic visit for VTE. – – 172 6.2 172 0 Surgeryaa Discharge diagnosis of fracture or surgery within 90 days before the hospital inpatient admission or outpatient hospital clinic visit for VTE. – – 507 18.4 507 0.1 Cancerbb Cancer diagnosed before or within 90 days after the VTE. – – 23 0.8 23 0 a Discharge diagnosis of fracture or surgery within 90 days before the hospital inpatient admission or outpatient hospital clinic visit for VTE. b Cancer diagnosed before or within 90 days after the VTE. c Information on pre-pregnancy body mass index (BMI) was obtained from the Medical Birth Registry for the years 2005–2012. Placenta-mediated pregnancy complications We present risk and effect estimates in Tables 2, S2 and S3. Preeclampsia occurred in 4.2% of pregnancies in the VTE group and in 2.7% of pregnancies in the comparison cohort (adjusted RD = 1.3%, 95% CI 0.6–2.0%; adjusted RR = 1.5, 95% CI 1.3–1.8). Stillbirth occurred in 0.7% of pregnancies in the VTE group and in 0.4% of pregnancies in the comparison cohort (adjusted RD = 0.3%, 95% CI 0.02–0.6%; adjusted RR = 1.8, 95% CI 1.1–3.0). Placental abruption occurred in 0.8% of pregnancies in the VTE group and in 0.5% of pregnancies in the comparison cohort (adjusted RD = 0.3%, 95% CI − 0.05–0.6%; adjusted RR = 1.6, 95% CI 1.1–2.4). Small-for-gestational-age infants accounted for 10.9% of live births in the VTE group and 9.8% of live births in the comparison cohort (adjusted RD = 0.6%, 95% CI − 0.5–1.7%; adjusted RR = 1.1, 95% CI 0.9–1.3). Table 2. Risk of placenta-mediated pregnancy complications for women with and without preconception venous thromboembolism (VTE) Number of events and absolute risk, n (%) Risk difference, % (95% confidence interval) Relative risk (95% confidence interval) No VTE VTE Total Crude Adjustedaa Analyses were adjusted for maternal age, parity, maternal smoking, diabetes, essential hypertension and chronic renal disease. Analysis of small-for-gestational-age infants was restricted to live-born deliveries, since birth weights were available for live-births only 10. Crude Adjustedaa Analyses were adjusted for maternal age, parity, maternal smoking, diabetes, essential hypertension and chronic renal disease. Analysis of small-for-gestational-age infants was restricted to live-born deliveries, since birth weights were available for live-births only 10. Total 962 210 (100) 2757 (100) 964 967 (100) – – – – Preeclampsia 26 145 (2.7) 116 (4.2) 26 261 (2.7) 1.5 (0.7–2.2) 1.3 (0.6–2.0) 1.6 (1.3–1.9) 1.5 (1.3–1.8) Stillbirth 3443 (0.4) 18 (0.7) 3461 (0.4) 0.3 (− 0.01–0.6) 0.3 (0.02–0.6) 1.8 (1.1–3.0) 1.8 (1.1–3.0) Placental abruption 4814 (0.5) 22 (0.8) 4836 (0.5) 0.3 (− 0.03–0.6) 0.3 (− 0.05–0.6) 1.6 (1.1–2.4) 1.6 (1.1–2.4) Small-for-gestational-ageaa Analyses were adjusted for maternal age, parity, maternal smoking, diabetes, essential hypertension and chronic renal disease. Analysis of small-for-gestational-age infants was restricted to live-born deliveries, since birth weights were available for live-births only 10. 93 398 (9.8) 296 (10.9) 93 694 (9.8) 1.1 (− 0.1–2.3) 0.6 (− 0.5–1.7) 1.1 (0.9–1.3) 1.1 (0.9–1.3) a Analyses were adjusted for maternal age, parity, maternal smoking, diabetes, essential hypertension and chronic renal disease. Analysis of small-for-gestational-age infants was restricted to live-born deliveries, since birth weights were available for live-births only 10. The crude and adjusted RDs and RRs did not differ substantially, indicating little net confounding by measured confounding factors (Tables 2, S2 and S3). The association between a preconception history of VTE and placenta-mediated complications was also consistent overall when DVT, PE, provoked VTE and unprovoked VTE were examined separately (Tables S2 and S3). The crude and adjusted RDs and RRs were largely unchanged after exclusion of immigrants (data not shown), minimizing any concern about left-truncation of VTE history. No striking effect-measure modification by maternal age, parity, previous preeclampsia or maternal pre-pregnancy BMI was evident for any of the outcomes (Figs. 2 and 3). Figure 2Open in figure viewerPowerPoint Adjusted risk ratios for placenta-mediated pregnancy complications according to history of venous thromboembolism in strata of maternal age and parity for all pregnancies leading to delivery during 1997–2012 in Denmark. Figure 3Open in figure viewerPowerPoint Adjusted risk ratios for placenta-mediated pregnancy complications according to history of venous thromboembolism in strata of pre-pregnancy body mass index (BMI) for all pregnancies leading to delivery during 2005–2012 in Denmark. Discussion We found that a preconception history of VTE increased the risk of placenta-mediated pregnancy complications. Thus, women with a preconception VTE were at increased risk of preeclampsia, stillbirth, placental abruption and small-for-gestational-age infants in subsequent pregnancies. An earlier case–control study investigated the prevalence of placenta-mediated complications in women with a preconception history of VTE (n = 75) compared with women with a first VTE after their last pregnancy (n = 197) 7. The relative risk was 0.9 (95% CI, 0.08–8.5) for preeclampsia and 1.0 (95% CI, 0.2–3.8) for stillbirth 7. A cohort study compared risk of preeclampsia and stillbirth in women with a history of VTE receiving low-molecular-weight heparin in subsequent pregnancies (n = 80) and women without previous VTE and who did not receive this treatment during pregnancy 8. The RR estimate was 3.0 (95% CI, 0.7–13.7) for preeclampsia and 0.4 (95% CI, 0.1–3.0) for stillbirth 8. These estimates indicated a possible association between VTE, preeclampsia and stillbirth. Consistent with the magnitude of our effect estimate, a Swedish registry-based cohort study found a crude odds ratio of 1.49 (95% CI, 1.26–1.76) for preeclampsia given a personal history of VTE (personal communication with Dr B. Zöller, 30 January 2015) 21. Placental thrombosis at least partly explains the placenta-mediated pregnancy complications 3. Thus, a fundamental propensity for thrombosis seems to be a biologically plausible link between VTE and placenta-mediated pregnancy complications 2, 3. Thrombophilia, a congenital or acquired abnormality in blood coagulation characterized by a propensity for thrombosis, has been intensely studied in relation to placenta-mediated complications. An association has largely been refuted, except for factor V Leiden and lupus anticoagulant, which are weakly associated with fetal loss 5, 22, 23. The present study demonstrates that the clinical phenotype of hypercoagulability – manifested as VTE – is a stronger predictor of placenta-mediated complications. Antenatal treatment with low-molecular-weight heparin has been postulated to prevent the placenta-mediated complications, but evidence supporting such a preventative effect is still lacking 24. Low-dose aspirin has been found to reduce the risk of recurrent preeclampsia if prescribed in early gestation 25. Our registry-based nationwide approach in the setting of a tax-paid healthcare system is likely to have eliminated selection biases. There may have been some misclassification of VTE diagnoses, but previous studies have demonstrated that the misclassified proportion of VTE diagnoses is not larger than 20% 13, 26, 27. Misclassification is possible for mild preeclampsia, small-for-gestational-age infants and placental abruption 17, 28-30. However, the potential misclassification is likely to be non-differential. Therefore, the resulting bias is likely to underestimate the magnitude of the association and would not explain our findings. There was a potential risk of left censoring, because data on VTE history before 1997 were not available in our registries. Adjustment for potential confounders did not greatly change our estimates, indicating little net confounding by measured variables. Residual confounding cannot be ruled out due to the observational design of the study. In conclusion, we found that women with a preconception history of VTE were at increased risk of placenta-mediated complications. Addendum A. T. Hansen, E. Horváth–Puhó, M. Schmidt and H. T. Sørensen contributed substantially to concept and design, analysis and interpretation of data, critical writing and revising the intellectual content, and final approval of the version to be published. L. Pedersen contributed substantially to concept and design, interpretation of data, revising the intellectual content, and final approval of the version to be published. A. M. Hvas and K. J. Rothman contributed substantially to concept and design, interpretation of data, critical writing and revising the intellectual content, and final approval of the version to be published. Disclosure of Conflict of Interests Funding was provided by the program for Clinical Research Infrastructure established by the Lundbeck Foundation and the Novo Nordisk Foundation. Supporting Information Filename Description jth13046-sup-0001-TableS1-S3.docWord document, 128 KB Table S1. International Classification of Diseases (ICD) codes obtained from the Danish National Patient Registry (DNPR) and outcome variables obtained from the Medical Birth Registry (MBR).Table S2. Risk of placenta-mediated pregnancy complications for women with and without preconception venous thromboembolism (VTE) by type of VTE. DVT, deep venous thrombosis; PE, pulmonary embolism.Table S3. Risk of placenta-mediated pregnancy complications for women with and without preconception venous thromboembolism (VTE) during 2005–2012, additionally adjusted for maternal pre-pregnancy body mass index. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. References 1Ananth CV, Peltier MR, Chavez MR, Kirby RS, Getahun D, Vintzileos AM. Recurrence of ischemic placental disease. Obstet Gynecol 2007; 110: 128– 33. CrossrefPubMedWeb of Science®Google Scholar 2Rodger MA, Carrier M, Le Gal G, Martinelli I, Perna A, Rey E, de Vries JI, Gris JC; Low-Molecular-Weight Heparin for Placenta-Mediated Pregnancy Complications Study Group. Meta-analysis of low-molecular-weight heparin to prevent recurrent placenta-mediated pregnancy complications. 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