Background
Despite concern for adverse perinatal outcomes in women with diabetes mellitus before pregnancy, recent data on the prevalence of pregestational type 1 and type 2 diabetes mellitus in the United States are lacking.
Objective
The purpose of this study was to estimate changes in the prevalence of overall pregestational diabetes mellitus (all types) and pregestational type 1 and type 2 diabetes mellitus and to estimate whether changes varied by race-ethnicity from 1996–2014.
Study Design
We conducted a cohort study among 655,428 pregnancies at a Northern California integrated health delivery system from 1996–2014. Logistic regression analyses provided estimates of prevalence and trends.
Results
The age-adjusted prevalence (per 100 deliveries) of overall pregestational diabetes mellitus increased from 1996–1999 to 2012–2014 (from 0.58 [95% confidence interval, 0.54–0.63] to 1.06 [95% confidence interval, 1.00–1.12]; P trend <.0001). Significant increases occurred in all racial-ethnic groups; the largest relative increase was among Hispanic women (121.8% [95% confidence interval, 84.4–166.7]); the smallest relative increase was among non-Hispanic white women (49.6% [95% confidence interval, 27.5–75.4]). The age-adjusted prevalence of pregestational type 1 and type 2 diabetes mellitus increased from 0.14 (95% confidence interval, 0.12–0.16) to 0.23 (95% confidence interval, 0.21–0.27; P trend <.0001) and from 0.42 (95% confidence interval, 0.38–0.46) to 0.78 (95% confidence interval, 0.73–0.83; P trend <.0001), respectively. The greatest relative increase in the prevalence of type 1 diabetes mellitus was in non-Hispanic white women (118.4% [95% confidence interval, 70.0–180.5]), who had the lowest increases in the prevalence of type 2 diabetes mellitus (13.6% [95% confidence interval, –8.0 to 40.1]). The greatest relative increase in the prevalence of type 2 diabetes mellitus was in Hispanic women (125.2% [95% confidence interval, 84.8–174.4]), followed by African American women (102.0% [95% confidence interval, 38.3–194.3]) and Asian women (93.3% [95% confidence interval, 48.9–150.9]).
Conclusions
The prevalence of overall pregestational diabetes mellitus and pregestational type 1 and type 2 diabetes mellitus increased from 1996–1999 to 2012–2014 and racial-ethnic disparities were observed, possibly because of differing prevalence of maternal obesity. Targeted prevention efforts, preconception care, and disease management strategies are needed to reduce the burden of diabetes mellitus and its sequelae.
Data on trends in the prevalence of pregestational diabetes mellitus and whether trends in the prevalence of pregestational type 1 and type 2 diabetes mellitus vary by race-ethnicity in the United States are needed. It has been reported that the predicted increases in the number of youths who will be living with type 1 and type 2 diabetes mellitus by the year 2050 will be primarily among youths of minority racial-ethnic groups, thus a similar racial-ethnic disparity in the prevalence of pregestational type 1 and type 2 diabetes mellitus might be expected. Three reports suggest that the prevalence of pregestational diabetes mellitus increased among pregnant women in the United States up to 2010. The only study that reported on trends in the prevalence of pregestational type 1 and type 2 diabetes mellitus did not include racial-ethnic specific prevalence estimates, and data were limited to 2004. Therefore, it is unknown whether increases in the prevalence of pregestational type 1 and type 2 diabetes mellitus vary by race-ethnicity.
Pregestational diabetes mellitus is associated with an increased risk of adverse perinatal outcomes that include preeclampsia, retinopathy, early fetal loss, stillbirth, macrosomia, birth injuries associated with large fetal size, and infant death. Given the burden of type 1 and type 2 diabetes mellitus during pregnancy and recent changes in the racial-ethnic composition of women of reproductive age in the United States, understanding changes in the prevalence of pregestational diabetes mellitus, overall and by population subgroups, is important for informing health systems and clinicians of the resources that are required for the preconception and obstetric care of young women with diabetes mellitus.
The objective of this study was to estimate trends in the prevalence of overall pregestational diabetes mellitus (ie, all types) and pregestational type 1 and type 2 diabetes mellitus (hereafter referred to as type 1 and type 2 diabetes mellitus) between 1996 and 2014 and to examine whether changes in prevalence vary by race-ethnicity.
Materials and Methods
The study setting is Kaiser Permanente Northern California (KPNC), a large integrated healthcare delivery system that consists of 44 medical centers and 13 delivery hospitals that provide healthcare for approximately 33,000 deliveries per year. Analysis of US census data demonstrates that KPNC members are representative of the geographic region served with regards to race-ethnicity and education and differ only slightly at the extremes of the income distribution. Women use the same KPNC medical center for general medicine and obstetric care, which includes all laboratory testing. KPNC maintains complete databases of all hospitalizations, outpatient visits, laboratory tests, and medications that are dispensed through an electronic health record system, in addition to housing a Diabetes Registry and a Pregnancy Glucose Tolerance and Gestational Diabetes Registry. All laboratory tests performed during and outside of pregnancy are determined at a single location, the KPNC Regional Laboratory, which participates in the College of American Pathologists’ accreditation and monitoring program.
This cohort study was conducted among pregnancies that delivered at ≥20 weeks gestation between January 1, 1996, and December 31, 2014. Deliveries were identified by a method previously described. Clinically recognized diabetes mellitus before a pregnancy (ie, overall pregestational diabetes mellitus) was ascertained through the KPNC Diabetes Registry. Study methods and description of the KPNC Diabetes Registry (99% sensitivity based on chart review validation) have been published previously. Briefly, in the Diabetes Registry, clinical recognition of diabetes mellitus is based on meeting any of the following criteria: (1) inpatient diagnosis of diabetes mellitus (principal diagnosis of ICD-9: 250), (2) ≥2 outpatient diagnoses of diabetes mellitus with ICD-9: 250 (excluding those collected in the emergency room, optometry, or ophthalmology departments), (3) outpatient laboratory test result of >6.7for HbA1c, or (4) pharmacy use (prescription for insulin or oral antihyperglycemic medications). Women are excluded from the Diabetes Registry if they are identified for the use of insulin sensitizers (thiazolidinediones or metformin), conditions other than diabetes mellitus (eg, lipodystrophy or polycystic ovarian syndrome) or if they were identified for 1 of the 4 criteria without a subsequent diabetes mellitus–related use within a 2-year period. Women were excluded from this study if, for a given pregnancy, they had gestational diabetes mellitus (ICD-9: 648.8) or met the diagnostic glucose thresholds for gestational diabetes mellitus according to the Carpenter and Coustan criteria, as assessed by linking with the KPNC Pregnancy Glucose Tolerance and Gestational Diabetes Registry.
Pregestational diabetes mellitus types were defined with the use of a combination of ICD-9 codes and insulin use in the following manner: (1) identified as pregestational type 2 diabetes mellitus if insulin was never used or used only during pregnancy (n=3200) or if insulin was used during pregnancy and in the year before conception and only ICD-9 codes for type 2 diabetes mellitus (ICD-9 250.x0, 250.x2) were present and no ICD-9 codes for type 1 diabetes mellitus (ICD-9 250.x1, 250.x3) were present (n=772); (2) identified as pregestational type 1 diabetes mellitus if insulin was used during pregnancy and in the year before conception and ICD-9 codes for type 1 diabetes mellitus were present (n=1250). Diabetes mellitus type was assigned “unknown” if neither of the aforementioned definitions were met and the pregnancy was excluded (n=34). Among the 1250 pregnancies defined has having pregestational type 1 diabetes mellitus, approximately 90% of them had at least 2 diagnoses of type 1 diabetes mellitus on different occasions.
Maternal age was obtained from electronic health records; self-reported race-ethnicity was obtained from the birth certificate. This study was approved by the human subjects committees of KPNC and the State of California.
Statistical analyses
The age-adjusted prevalence of pregestational diabetes mellitus per 100 deliveries (95% confidence interval [CI]) was obtained from logistic regression analyses that were conducted among 655,428 pregnancies that delivered at ≥20 weeks gestation from 1996–2014. Time trends in the age-adjusted prevalence of overall pregestational diabetes mellitus and pregestational type 1 and type 2 diabetes mellitus (per 100 deliveries) were evaluated among all women and by race-ethnicity, with years grouped 1996–1999, 2000–2002, 2003–2005, 2006–2008, 2009–2011 and 2012–2014. Differences by race-ethnicity were obtained from logistic regression models that included the racial-ethnic groups as dummy variables. The probability values for the parameters that were calculated for each racial-ethnic group were obtained from maximum likelihood estimation. All analyses were performed with SAS software (version 9.3; SAS Institute Inc, Cary, NC).
Results
Among 655,428 pregnancies that were delivered at ≥20 weeks gestation between January 1, 1996, and December 31, 2014, at KPNC, 5256 pregnancies (0.8%) were identified as affected by pregestational diabetes mellitus. Of these, 1250 pregnancies (23.8%) were classified as type 1 diabetes mellitus, and 3972 pregnancies (75.6%) were classified as type 2 diabetes mellitus; for 34 pregnancies (0.6%), diabetes mellitus type was classified as unknown and were excluded. Table 1 presents characteristics of the study cohort according to pregestational diabetes mellitus status and type. Women with pregestational type 2 diabetes mellitus were more likely to be older (ie, ≥30 years old) than both women without pregestational diabetes mellitus and women with pregestational type 1 diabetes mellitus. As compared with women without pregestational diabetes mellitus, women with pregestational type 1 diabetes mellitus were more likely to be non-Hispanic white; women with pregestational type 2 diabetes mellitus were more likely to be African American, Asian, or Hispanic.
| Variable | Pregnancies, n % | ||
|---|---|---|---|
| Without recognized pregestational diabetes mellitus (n= 650,206) | With pregestational type 1 diabetes mellitus (n= 1250) | With pregestational type 2 diabetes mellitus (n= 3972) | |
| Age, y | |||
| <20 | 37,138 (5.7) | 51 (4.1) | 39 (1.0) |
| 20-29 | 282,628 (43.5) | 518 (41.4) | 900 (22.7) |
| 30-39 | 300,207 (46.2) | 620 (49.6) | 2550 (64.2) |
| ≥40 | 26,116 (4) | 58 (4.6) | 469 (11.8) |
| Missing | 4,117 (0.6) | 3 (0.2) | 14 (0.3) |
| Race-ethnicity | |||
| Non-Hispanic White | 262,362 (40.4) | 716 (57.3) | 973 (24.5) |
| African American | 46,190 (7.1) | 119 (9.5) | 413 (10.4) |
| Asian | 121,906 (18.7) | 109 (8.7) | 915 (23.0) |
| Hispanic | 159,007 (24.5) | 241 (19.3) | 1377 (34.7) |
| Other | 47,223 (7.3) | 53 (4.2) | 248 (6.2) |
| Missing | 13,518 (2.1) | 12 (1.0) | 46 (1.2) |
Table 2 displays the crude and age-adjusted prevalence of overall pregestational diabetes mellitus per 100 deliveries. The age-adjusted prevalence of overall pregestational diabetes mellitus increased from 1996–1999 to 2009–2011 and then leveled off in 2012–2014 (from 0.58 [95% CI, 0.54–0.63] to 1.06 [95% CI, 1.00–1.12] per 100 deliveries; P trend <.0001). Increases in the age-adjusted prevalence of overall pregestational diabetes mellitus were observed for all racial-ethnic groups (all P trend <.0001); the largest relative increases were observed among Hispanic women (121.8% [95% CI, 84.4–166.7]); the smallest relative increases were observed among non-Hispanic white women (49.6% [95% CI, 27.5–75.4]).
| Variable | 1996–1999 (n= 124,825) | 2000–2002 (n= 102,060) | 2003–2005 (n= 103,701) | 2006–2008 (n= 109,200) | 2009–2011 (n= 104,901) | 2012–2014 (n= 110,775) | % Change a | P for trend |
|---|---|---|---|---|---|---|---|---|
| All women | ||||||||
| Crude | 0.50 | 0.57 | 0.76 | 0.91 | 1.03 | 1.04 | 108 | |
| Age-adjusted | 0.58 (0.54–0.64) | 0.65 (0.60–0.71) | 0.82 (0.77–0.89) | 0.98 (0.92–1.04) | 1.08 (1.02–1.15) | 1.06 (1.00–1.13) | 82.5 | <.0001 |
| Non-Hispanic white women | ||||||||
| Crude | 0.49 | 0.52 | 0.64 | 0.72 | 0.75 | 0.78 | 59.2 | |
| Age-adjusted | 0.54 (0.48–0.61) | 0.57 (0.50–0.65) | 0.68 (0.61–0.78) | 0.77 (0.68–0.86) | 0.79 (0.71–0.89) | 0.80 (0.72–0.89) | 49.6 (27.4–75.2) | <.0001 |
| African American women | ||||||||
| Crude | 0.64 | 1.02 | 1.42 | 1.30 | 1.32 | 1.25 | 95.3 | |
| Age-adjusted | 0.81 (0.67–1.10) | 1.24 (0.99–1.60) | 1.68 (1.37–2.08) | 1.59 (1.33–1.93) | 1.54 (1.27–1.86) | 1.41 (1.17–1.74) | 75.8 | <.0001 |
| Asian women | ||||||||
| Crude | 0.53 | 0.44 | 0.60 | 0.92 | 1.09 | 1.09 | 106 | |
| Age-adjusted | 0.55 (0.45–0.69) | 0.45 (0.36–0.59) | 0.59 (0.49–0.72) | 0.87 (0.75–1.01) | 0.99 (0.86–1.13) | 0.96 (0.84–1.09) | 73.8 | <.0001 |
| Hispanic women | ||||||||
| Crude | 0.57 | 0.65 | 1.05 | 1.08 | 1.29 | 1.49 | 161 | |
| Age-adjusted | 0.74 (0.65–0.87) | 0.81 (0.70–0.95) | 1.23 (1.09–1.39) | 1.26 (1.13–1.41) | 1.44 (1.32–1.63) | 1.63 (1.49–1.84) | 121.8 | <.0001 |
a Indicates rate change from 1996–1999 to 2012–2014 prevalence estimates.
Significant increases in the prevalence of both pregestational type 1 and type 2 diabetes mellitus were observed ( Tables 3 and 4 ).The age-adjusted prevalence of type 1 diabetes mellitus increased from 1996–1999 to 2009–2011and then leveled off in 2012–2014 (from 0.14 [95% CI, 0.12–0.16] in 1996–1999 to 0.24 [95% CI, 0.21–0.27] per 100 deliveries in 2012–2014; P trend <.0001; Table 3 ). The age-adjusted prevalence of type 2 diabetes mellitus increased from 1996–1999 to 2012–2014 (from 0.42 [95% CI, 0.38–0.46] to 0.78 [95% CI, 0.73–0.83] per 100 deliveries; P trend <.0001; Table 4 ). Racial and ethnic disparities were observed for trends in the age-adjusted prevalence of pregestational type 1 and type 2 diabetes mellitus ( Tables 3 and 4 ). From 1996–1999 to 2012–2014, non-Hispanic white women had the largest relative increase in the age-adjusted prevalence of pregestational type 1 diabetes mellitus (118.4% [70.0–180.5]; P trend <.0001) and the smallest relative increases in the age-adjusted prevalence of pregestational type 2 diabetes mellitus (13.6% [95% CI, -8.0–40.1]; P trend >.05). From 1996–1999 to 2012–2014, Hispanic women had the largest relative increases in the age-adjusted prevalence of pregestational type 2 diabetes mellitus (125.2% [95% CI, 84.8–174.4]; P trend <.0001) and a large increase in the age-adjusted prevalence of pregestational type 1 diabetes mellitus (88.3% [12.5–215.3]; P trend <.0001). African American and Asian women had small statistically nonsignificant relative changes in the age-adjusted prevalence of pregestational type 1 diabetes mellitus from 1996–1999 to 2012–2014 (17.0% [95% CI, -38.1–121.4] and –18.4% [95% CI, -57.2–55.4], respectively; P trend >.05) and large statistically significant increases in the age-adjusted prevalence of pregestational type 2 diabetes mellitus from 1996–1999 to 2012–2014 (102.0% [95% CI, 38.3–194.3] and 93.3% [95% CI, 48.9–150.9], respectively; P trend <.0001].
| Variable | 1996–1999 (n= 124,825) | 2000–2002 (n= 102,060) | 2003–2005 (n= 103,701) | 2006–2008 (n= 109,200) | 2009–2011 (n= 104,901) | 2012–2014 (n= 110,775) | % Change a | P for trend |
|---|---|---|---|---|---|---|---|---|
| All women | ||||||||
| Crude | 0.13 | 0.13 | 0.18 | 0.20 | 0.28 | 0.23 | 76.9 | |
| Age-adjusted | 0.14 (0.12–0.16) | 0.13 (0.11–0.16) | 0.19 (0.16–0.22) | 0.20 (0.18–0.23) | 0.29 (0.25–0.32) | 0.24 (0.21–0.27) | 73.2 (42.2–110.9) | <.0001 |
| Non-Hispanic white women | ||||||||
| Crude | 0.17 | 0.18 | 0.25 | 0.29 | 0.39 | 0.38 | 124 | |
| Age-adjusted | 0.17 (0.14–0.20) | 0.17 (0.14–0.22) | 0.24 (0.20–0.30) | 0.28 (0.23–0.34) | 0.37 (0.32–0.44) | 0.36 (0.31–0.43) | 118.4 (70.0–180.5) | <.0001 |
| African American women | ||||||||
| Crude | 0.20 | 0.23 | 0.34 | 0.21 | 0.33 | 0.24 | 20.0 | |
| Age-adjusted | 0.23 (0.14–0.37) | 0.26 (0.16–0.44) | 0.38 (0.24–0.58) | 0.24 (0.15–0.39) | 0.37 (0.25–0.54) | 0.27 (0.17–0.43) | 17.0 (–38.1–121.4) | .43 |
| Asian women | ||||||||
| Crude | 0.10 | 0.03 | 0.10 | 0.09 | 0.12 | 0.08 | –20.0 | |
| Age-adjusted | 0.11 (0.07–0.18) | 0.04 (0.02–0.09) | 0.11 (0.07–0.18) | 0.10 (0.06–0.15) | 0.13 (0.09–0.19) | 0.09 (0.06–0.14) | –18.4 (–57.2–55.4) | .57 |
| Hispanic women | ||||||||
| Crude | 0.08 | 0.09 | 0.16 | 0.16 | 0.26 | 0.16 | 100 | |
| Age-adjusted | 0.08 (0.05–0.13) | 0.09 (0.06–0.14) | 0.17 (0.12–0.23) | 0.16 (0.12–0.22) | 0.26 (0.20–0.34) | 0.16 (0.11–0.22) | 88.3 (12.5–215.3) | <.0001 |
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