Objective
The Centers for Disease Control and Prevention last estimated a national ectopic pregnancy rate in 1992, when it was 1.97% of all reported pregnancies. Since then rates have been reported among privately insured women and regional health care provider populations, ranging from 1.6–2.45%. This study assessed the rate of ectopic pregnancy among Medicaid beneficiaries (New York, California, and Illinois, 2000-03), a previously unstudied population.
Study Design
We identified Medicaid administrative claims records for inpatient and outpatient encounters with a principal International Classification of Diseases 9th Revision diagnosis code for ectopic pregnancy. We calculated the ectopic pregnancy rate among female beneficiaries aged 15-44 as the number of ectopic pregnancies divided by the number of total pregnancies, which included spontaneous abortions, induced abortions, ectopic pregnancies, and all births. We used Poisson regression to assess the risk of ectopic pregnancy by age and race.
Results
Four-year Medicaid ectopic pregnancy rates were 2.38% of pregnancies in New York, 2.07% in California, and 2.43% in Illinois. Risk was higher among black women compared with whites in all states (relative risk, 1.26; 95% confidence interval, 1.25–1.28; P < .0001), and among older women compared with younger women (trend for age, P < .001).
Conclusion
Medicaid beneficiaries in these 3 states experienced higher rates of ectopic pregnancy than reported for privately insured women nationwide in the same years. Relying on private insurance databases may underestimate ectopic pregnancy’s burden in the United States population. Furthermore, within this low-income population racial disparities exist.
Ectopic pregnancy is an important cause of maternal morbidity and mortality in the United States. Defined as implantation of a fertilized egg outside the uterine endometrium, ectopic pregnancy caused an estimated 876 US deaths between 1980 and 2007. In 1992 the Centers for Disease Control and Prevention (CDC) estimated the US ectopic pregnancy rate at 1.97% of all pregnancies. Since then, CDC has acknowledged that their surveillance using national health care surveys no longer produces a reliable ectopic pregnancy rate. This is primarily because ectopic pregnancy care has changed to involve multiple health care encounters in different settings: emergency department, outpatient, and inpatient. CDC surveys do not track individual patients through multiple health care visits so they risk over- or undercounting cases. Instead, researchers have moved to using insurance-based databases in which encounters can be linked to calculate ectopic pregnancy rates within their covered populations. Van Den Eeden and colleagues reported a rate within Kaiser Permanente Northern California of 2.07% during 1997-2000. Trabert and colleagues reported that among patients at Group Health Cooperative, a health plan serving Washington and Idaho, the rate increased from 1.78% in 1993-95, to 2.45% in 2005-07. Hoover and colleagues reported a 2002-07 treated ectopic pregnancy rate of 0.64% among women in MarketScan, a nationwide administrative database of more than 200 US commercial insurers; looking at all ectopic pregnancy diagnoses, the rate in this population was 1.6.
Prior research gives indirect evidence that ectopic pregnancy may be more prevalent among low-income women than in the general population. For example, CDC surveillance from 1970-89 found higher rates among nonwhite women compared with whites in all age groups and across all years (rate ratio = 1.4), without controlling for socioeconomic factors. Because nonwhites were more likely to be poor compared with whites in the US during this surveillance period, it is impossible to know if the observed racial disparity was attributable–in part or entirely–to socioeconomic factors and access to appropriate health care services. The hypothesis that access to care plays an important role is supported by the fact that the racial disparity is even greater for ectopic pregnancy mortality than it is for ectopic pregnancy incidence. From 2003-07, the ectopic pregnancy mortality ratio (deaths per 100,000 live births) was 6.8 times higher for African American women compared with whites. Recent studies assessing access to urgent care for ectopic pregnancy and outcomes from ectopic pregnancy hospitalizations confirm that women with Medicaid or no insurance are disproportionately affected. However, no studies have directly examined ectopic pregnancy rates among low-income women. Previous insurance population studies have included few or no Medicaid beneficiaries: Kaiser Permanente Northern California and Group Health Cooperative each estimate that approximately 5% of their population is insured by Medicaid, whereas the MarketScan database includes private insurance only.
Medicaid, the public insurance program for low-income residents of the US, covers 12% of all nonelderly women in the US, and 41% of all births. We conducted this study to measure the rate of ectopic pregnancy among Medicaid beneficiaries in 3 of the largest US states during the years 2000 through 2003, the most recent years for which data were available when this study was initiated. We also aimed to assess whether the racial disparity in ectopic pregnancy rate that has previously been reported for the US population is observed within the Medicaid population.
Materials and Methods
We obtained Medicaid Analytic Extract data files from the Centers for Medicare and Medicaid Services (CMS) under an approved Data Use Agreement. The University of Chicago Biological Sciences Institutional Review Board acknowledged the study as exempt from review, as is typical with studies involving analysis of existing deidentified data. We examined Medicaid claims for all female Medicaid beneficiaries aged 6-64 years of age in New York, California, and Illinois, 2000-03. These states represent 24% of births in the US, are located in different regions of the country and are each racially and ethnically diverse. These data files include person-level information on Medicaid enrollees and encounter-level information for all Medicaid claims for inpatient hospital care and other therapies such as physician services, radiology, and clinic visits. We limited our analysis to women aged 15-44 to make it comparable to other studies of women of reproductive age.
We identified ectopic pregnancy cases from both inpatient and outpatient claims containing the International Classification of Diseases 9th revision (ICD9) diagnosis code 633.xx as principal diagnosis. We calculated the ectopic pregnancy rate among beneficiaries aged 15-44 as the number of ectopic pregnancies (by principal diagnosis code) divided by the number of total pregnancies, identified using ICD9 diagnosis codes for all pregnancy-related care and outcomes ( Table 1 ). Encounters with one of these codes in any diagnosis field–principal, secondary, or other–were included in the denominator. This strategy was designed to produce the most conservative (lowest) estimate of the ectopic pregnancy rate, because the case definition for the numerator required a principal diagnosis of ectopic pregnancy, whereas any possible pregnancy would be captured in the denominator. We conducted exploratory analyses to determine the effect of adjusting the numerator and denominator case definitions by making them broader (by including more diagnosis codes) or narrower (fewer diagnosis codes).
| Diagnosis | ICD9 code | Diagnosis field (variable) |
|---|---|---|
| Ectopic pregnancy | 633.xx | Principal diagnosis |
| All pregnancies | ||
| Ectopic, molar, or abortive | 63x.xx | Principal, secondary, or other diagnosis |
| Complications of pregnancy | 64x.xx | Principal, secondary, or other diagnosis |
| Normal labor and delivery | 65x.xx | Principal, secondary, or other diagnosis |
| Complications of labor and delivery | 66x.xx | Principal, secondary, or other diagnosis |
| Normal pregnancy | V22.xx | Principal, secondary, or other diagnosis |
| High-risk pregnancy | V23.xx | Principal, secondary, or other diagnosis |
| Outcome of delivery | V27.xx | Principal, secondary, or other diagnosis |
| Antenatal screening | V28.xx | Principal, secondary, or other diagnosis |
For both the numerator and denominator counts, repeat pregnancy-related encounters within 9 months (270 days) were considered part of the same pregnancy. Repeat pregnancy-related encounters for the same beneficiary after 9 months were treated as a new pregnancy episode and each pregnancy episode (in 9-month groupings of claims) was counted separately. We further conducted exploratory analysis to determine the effect on rate calculations of varying this time definition of a single pregnancy, comparing our 9-month assumption with shorter (6 month) and longer (10 month) assumptions.
We examined ectopic pregnancy rates by race/ethnicity and age group. Age was calculated by subtracting the beginning date of service for the first pregnancy encounter from the beneficiary’s date of birth. Race/ethnicity was obtained from the Inpatient and Other Therapy files. The race/ethnicity variable in Medicaid files is coded as: white, black, Hispanic, Asian, American indian/Alaskan native, native Hawaiian/Pacific Islander, or multiracial. Because the outcome variable was a rate, we used Poisson multivariable regression models to estimate the relative risks for ectopic pregnancy by race/ethnicity and age group within each state.
Results
There were 19,132,067 person-years of enrollment in Medicaid among women aged 15-44 in New York, California, and Illinois combined during the 2000-03 period ( Table 2 ), representing 8,452,457 unique individuals. Overall, there were 48,500 unique cases of ectopic pregnancy in this population, and 2,182,042 total pregnancies, for an ectopic pregnancy rate of 2.22% (2.22 per 100 reported pregnancies) or 2.54 per 1000 woman-years. Table 3 presents ectopic pregnancy rates for each state, stratified by race/ethnicity, and age group. The ectopic pregnancy rate is similar among white women in each state: 2.26% in New York, 2.29% in California, and 2.45% in Illinois. The ectopic pregnancy rate among black women is greater than 3% in both Illinois and California.
| Demographic | New York (n = 3,644,214) n (%) | California (n = 13,686,040) n (%) | Illinois (n = 1,801,813) n (%) |
|---|---|---|---|
| Age group | |||
| 15-19 | 710,708 (19.5) | 2,964,083 (22.2) | 415,703 (23.1) |
| 20-24 | 741,069 (20.4) | 321,7602 (24.1) | 407,900 (22.6) |
| 25-29 | 606,778 (16.7) | 2,653,940 (19.9) | 329,315 (18.3) |
| 30-34 | 560,527 (15.4) | 2,096,293 (15.7) | 251,881 (14.0) |
| 35-39 | 528,670 (14.5) | 1,536,423 (11.5) | 198,702 (11.0) |
| 40-44 | 363,716 (10.0) | 879,392 (6.6) | 116,795 (6.5) |
| Unknown/not documented | 132,746 (3.6) | 338,307 (6.6) | 81,517 (4.5) |
| Race/ethnicity | |||
| White | 1,071,643 (29.4) | 2,865,284 (20.9) | 640,624 (35.6) |
| Black | 956,814 (26.3) | 1,243,927 (9.1) | 748,454 (41.5) |
| American Indian/Alaskan native | 66,635 (1.8) | 66,570 (0.5) | 3493 (0.2) |
| Asian | 150,489 (4.1) | 593,274 (4.3) | 33,517 (1.9) |
| Hispanic | 703,674 (19.1) | 8,190,938 (59.9) | 341,632 (19.0) |
| Native Hawaiian/Pacific Islander | 0 (0.0) | 324,555 (2.4) | 0 (0.0) |
| More than 1 race | 0 (0.0) | 0 (0.0) | 1194 (0.1) |
| Unknown/not documented | 694,959 (19.1) | 401,492 (2.9) | 32,899 (1.8) |
| Variable | No. of ectopic pregnancies (A) | No. of total pregnancies (B) | Ectopic pregnancy rate (A/B) × 100 |
|---|---|---|---|
| New York | 15,224 | 638,849 | 2.38% |
| Race/ethnicity | |||
| White | 4738 | 209,462 | 2.26% |
| Black | 4658 | 182,786 | 2.55% |
| American Indian/Alaskan native | 279 | 23,087 | 1.21% |
| Asian | 401 | 33,773 | 1.19% |
| Hispanic | 3240 | 117,437 | 2.76% |
| Unknown/missing | 1908 | 72,304 | 2.64% |
| Age group | |||
| 15-19 | 1389 | 86,449 | 1.61% |
| 20-24 | 4662 | 205,845 | 2.26% |
| 25-29 | 3888 | 161,651 | 2.41% |
| 30-34 | 2858 | 106,077 | 2.69% |
| 35-39 | 1837 | 59,000 | 3.11% |
| 40-44 | 590 | 19,827 | 2.98% |
| California | 24,047 | 1,163,036 | 2.07% |
| Race/ethnicity | |||
| White | 4236 | 185,034 | 2.29% |
| Black | 3194 | 102,234 | 3.12% |
| American Indian/Alaskan native | 125 | 5355 | 2.33% |
| Asian | 878 | 44,162 | 1.99% |
| Hispanic | 14,487 | 752,066 | 1.93% |
| Native Hawaiian/Pacific Islands | 555 | 26,376 | 2.10% |
| Unknown/missing | 572 | 47,809 | 1.20% |
| Age group | |||
| 15-19 | 2403 | 183,790 | 1.31% |
| 20-24 | 6585 | 373,876 | 1.76% |
| 25-29 | 6364 | 288,755 | 2.20% |
| 30-34 | 4819 | 187,434 | 2.57% |
| 35-39 | 2843 | 97,082 | 2.93% |
| 40-44 | 1033 | 32,099 | 3.22% |
| Illinois | 9229 | 380,157 | 2.43% |
| Race/ethnicity | |||
| White | 2624 | 117,489 | 2.45% |
| Black | 3786 | 119,378 | 3.51% |
| American Indian/Alaskan native | 21 | 730 | 3.11% |
| Asian | 156 | 8969 | 1.90% |
| Hispanic | 2502 | 120,432 | 2.29% |
| Multiracial | 15 | 1013 | 1.50% |
| Unknown/missing | 125 | 12,146 | 1.21% |
| Age group | |||
| 15-19 | 1295 | 67,481 | 1.92% |
| 20-24 | 3295 | 142,193 | 2.32% |
| 25-29 | 2451 | 92,039 | 2.66% |
| 30-34 | 1377 | 49,442 | 2.79% |
| 35-39 | 663 | 22,493 | 2.95% |
| 40-44 | 148 | 6509 | 2.27% |
Table 4 presents the multivariable regression models for risk of ectopic pregnancy that include both race/ethnicity and age, separately by state. In all 3 states, the age-adjusted risk of ectopic pregnancy was statistically significantly higher among African American women and lower among Asian women in comparison to white women. The risk associated with Hispanic and American indian race/ethnicity varied by state. (The interaction between race/ethnicity and state was significant when tested in a pooled model that included all 3 states.) In the states where they were identified, native Hawaiian/Pacific Islander and multiracial women were at lower risk of ectopic pregnancy than white women.
| Demographic | New York | California | Illinois | ||||||
|---|---|---|---|---|---|---|---|---|---|
| RR | 95% CI | P value | RR | 95% CI | P value | RR | 95% CI | P value | |
| Race/Ethnicity | |||||||||
| White | Reference | Reference | Reference | ||||||
| Black | 1.12 | 1.1–1.14 | < .0001 | 1.36 | 1.34–1.39 | < .0001 | 1.45 | 1.42–1.48 | < .0001 |
| American Indian/Alaskan native | 0.56 | 0.50–0.56 | < .0001 | 1.04 | 0.96–1.12 | .3416 | 1.27 | 1.05–1.55 | .0141 |
| Asian | 0.49 | 0.47–0.51 | < .0001 | 0.79 | 0.77–0.81 | < .0001 | 0.73 | 0.68–0.79 | < .0001 |
| Hispanic | 1.21 | 1.19–1.24 | < .0001 | 0.83 | 0.82–0.84 | < .0001 | 0.90 | 0.88–0.93 | < .0001 |
| Native Hawaiian/Pacific Islands | — | — | — | 0.85 | 0.82–0.88 | < .0001 | — | — | — |
| Multiracial | — | — | — | — | — | — | 0.68 | 0.55–0.85 | .0008 |
| Unknown/missing | 1.07 | 1.05–1.10 | < .0001 | 0.71 | — | — | 0.45 | 0.41–0.49 | < .0001 |
| Age group | |||||||||
| 15-49 | Reference | Reference | Reference | ||||||
| 20-24 | 1.43 | 1.40–1.48 | < .0001 | 1.31 | 1.28–1.33 | < .0001 | 1.26 | 1.23–1.30 | < .0001 |
| 25-29 | 1.55 | 1.51–1.60 | < .0001 | 1.65 | 1.62–1.69 | < .0001 | 1.49 | 1.45–1.54 | < .0001 |
| 30-34 | 1.74 | 1.69–1.79 | < .0001 | 1.93 | 1.89–1.97 | < .0001 | 1.59 | 1.54–1.65 | < .0001 |
| 35-39 | 2.00 | 1.94–2.06 | < .0001 | 2.20 | 2.15–2.25 | < .0001 | 1.67 | 1.60–1.75 | < .0001 |
| 40-44 | 1.91 | 1.83–1.98 | < .0001 | 2.40 | 2.32–2.47 | < .0001 | 1.22 | 1.13–1.31 | < .0001 |
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