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AJR 2001; 176:123-127
© American Roentgen Ray Society

Expectant Treatment of Ectopic Pregnancies

Clinical and Sonographic Predictors

Mostafa Atri1,2, Chi-Ming Chow3, George Kintzen1, Peter Gillett4, Ann A. Aldis1, Micheline Thibodeau1, Caroline Reinhold1 and Patrice M. Bret1,5

1 Department of Radiology, McGill University, Montreal General Hospital, 1650 Ave. Cedar, Montreal, Quebec H3G 1A4, Canada.
2 Present address: Department of Medical Imaging, University of Toronto, Sunnybrook and Women's College Health Sciences Centre, 2075 Bayview Ave., Toronto, Ontario M3N 3M5, Canada.
3 Department of Epidemiology & Biostatistics, McGill University, 1020 Pine Ave. W., Montreal, Quebec H3A 1A2, Canada.
4 Department of Obstetrics and Gynecology, McGill University, Montreal General Hospital, Montreal, Quebec H3G 1A4, Canada.
5 Present address: Department of Medical Imaging, University of Toronto, University Health Network and Mount Sinai Hospital, 610 University Ave., Toronto, Ontario M5G 2M9, Canada.

Received April 19, 2000; accepted after revision June 20, 2000.

 
Address correspondence to M. Atri.


Abstract
Top
 Abstract
Introduction
 Subjects and Methods
 Results
 Discussion
 References
 
OBJECTIVE. We identified the potential clinical and sonographic predictors of the spontaneous resolution of ectopic pregnancies.

SUBJECTS AND METHODS. We performed a prospective study of 78 consecutive patients with a transvaginal sonographic diagnosis of ectopic pregnancy who had either two consecutive quantitative measurements of their beta subunit of human chorionic gonadotropin (ß-hCG) more than 24 hrs apart or an embryo with a heart beat. We evaluated the patient's age, time from the last menstrual period, ß-hCG level, size of ectopic pregnancy, presence of a gestational sac or embryonic elements, vascularity on color Doppler sonography, peak systolic velocity, and resistive index of ectopic pregnancy at the time of presentation as potential independent predictors of the final outcome. Logistic regression was performed to identify the independent predictors.

RESULTS. Forty-six patients had declining ß-hCG levels, and 32 ectopic pregnancies showed an embryo with a heart beat or had steady or rising ß-hCG levels. Univariate analysis indicated that a longer time from the last menstrual period (older ectopic pregnancies), lower ß-hCG levels, and the absence of gestational sac are statistically more significantly seen in ectopic pregnancies with declining ß-hCG levels (p < 0.05). Resistive index of ectopic pregnancy reached borderline significance (p = 0.05). In a multiple logistic model, the same variables were independent predictors of outcome (p < 0.05). Resistive index was also a predictor (p = 0.09).

CONCLUSION. Longer times from the last menstrual period, lower ß-hCG levels, absence of gestational sacs, and higher resistive indexes of ectopic pregnancy at the time of presentation appear to be independent predictors of the spontaneous resolution of ectopic pregnancy.


Introduction
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 Abstract
 Introduction
Subjects and Methods
 Results
 Discussion
 References
 
The prevalence of ectopic pregnancy has increased more than threefold from 4.5 per 1000 pregnancies in 1970 to 16.8 per 1000 in 1987 [1]. Although this is mostly attributed to the increasing prevalence of fallopian tube disease, it is partly explained by the detection of ectopic pregnancies that would have remained undetected and spontaneously resolved. The earlier and more accurate preoperative detection of ectopic pregnancy has been made possible by the combination of a highly sensitive screening test (i.e., radioimmunoassay of the beta subunit of human chorionic gonadotropin [ß-hCG]) and an accurate imaging test (transvaginal sonography) [2,3,4]. The spontaneous resolution of ectopic pregnancy, allowing the expectant treatment of some patients, is a recognized phenomenon [5,6,7,8,9,10,11,12]. Recently, there has been increasing interest in the expectant treatment of ectopic pregnancy because of the increasing detection of this condition and a trend toward a more conservative nonsurgical treatment of ectopic pregnancy [13,14,15,16,17,18,19,20]. The only effective predictor of the spontaneous resolution of ectopic pregnancy is declining quantitative ß-hCG levels. However, serial ß-hCG levels would generally require a delay of 24 hr to suggest spontaneous resolution. In a previously reported series, the spontaneously resolved ectopic pregnancies appeared to be less vascular than the growing ectopic pregnancies that required treatment [15]. The purpose of this study was to evaluate different potential clinical and sonographic predictors for the outcome of ectopic pregnancy that would suggest spontaneous resolution at the time of presentation. We considered two outcomes: first, spontaneous resolution treated expectantly versus growing ectopic pregnancy requiring treatment, and second, the ß-hCG trend.


Subjects and Methods
Top
 Abstract
 Introduction
 Subjects and Methods
Results
 Discussion
 References
 
This prospective study was conducted between January 1994 and June 1997 on consecutive patients with transvaginal sonographic diagnosis of ectopic pregnancy to determine the potential predictors of expectant treatment. Inclusion criteria were ectopic pregnancies containing an embryo with a heart beat on transvaginal sonography or ectopic pregnancies in patients who had two consecutive quantitative ß-hCG levels performed more than 24 hr apart. One hundred three patients had transvaginal sonographic diagnosis of ectopic pregnancy during this period. Twenty-five patients were excluded because they were treated medically or surgically immediately after transvaginal sonographic diagnosis for the following reasons and did not have two consecutive ß-hCG levels: the patient or surgeon opted for treatment, the patient was unstable, or there was suggestion of rupture of ectopic pregnancy clinically or on transvaginal sonography (the presence of fluid on sonography extending beyond the pelvis generally associated with a poorly defined ectopic pregnancy). These patients were excluded because, in the absence of two consecutive quantitative ß-hCG levels or an embryo with heart beat, it was impossible to determine if they represented growing ectopic pregnancies or if they could have been treated expectantly. Therefore, our study population included 78 patients. With respect to age, time from the last menstrual period, size of ectopic pregnancy, and ß-hCG level, there was no significant difference between the study group and the group that did not meet inclusion criteria with the exception of size difference (p = 0.04) (Table 1).


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  		TABLE 1 Demographics of Study Group and Immediately Treated Group

 

All patients (with the exception of those with ectopic pregnancies containing an embryo with heart beat) underwent two consecutive ß-hCG level measurements more than 24 hr apart. The first ß-hCG level measurement was obtained within 24 hr of transvaginal sonography. More than a 15% drop in ß-hCG level was considered a potential indicator for expectant treatment. Patients with less than a 15% drop in serum ß-hCG level and those with increasing ß-hCG levels underwent medical (intramuscular methotrexate) or surgical treatment. Patients considered for expectant treatment underwent follow-up quantitative ß-hCG until their level reached zero. Patients were between 18 and 41 years old (mean age, 32 years). The time from the last menstrual period at the time of presentation varied from 4 to 12 weeks (mean, 7 weeks).

We examined all patients with sonography using a transvaginal approach. All patients had empty bladders. Suprapubic examination was performed only if the adnexal regions were not adequately visible on transvaginal examination. An XP128 (Acuson, Mountain View, CA) or a SS270 (Toshiba, Markham, Ontario, Canada) scanner was used for sonography. The transvaginal probes ranged from 5 MHz to 7 MHz. As previously described [2], we used a predominantly solid extraovarian adnexal mass as the criterion required to diagnose ectopic pregnancy. Although lower sensitivity of this sign is reported in some series [21,22,23], in our practice and others [2,3,4], this sign has high sensitivity. All our patients had a predominantly solid extraovarian adnexal mass on transvaginal sonography. This finding has been shown to have a high specificity to diagnose ectopic pregnancy in a patient with a positive pregnancy test [3, 24]. Although it is theoretically possible that a nonvascular extraovarian adnexal mass with a declining ß-hCG level may represent an aborting intrauterine pregnancy (trophoblast in regression) with retrograde passage of blood into the fallopian tubes, this phenomenon is rare as indicated by the high specificity of this sign in the literature [3, 24]. Moreover, both conditions would require expectant treatment.

The age of the patient, the last menstrual period at the time of presentation, and the ß-hCG level within 24 hr of transvaginal sonography were recorded. Serum ß-hCG levels were quantified using the third international standard (international reference point). The sonographic data were collected by the sonologist who performed the sonographic examination. In our laboratory, the technologists initially perform the sonographic examinations that are reviewed real-time by one of five physicians involved with sonography. The mean diameter of the extraovarian adnexal mass, measured in three planes, and presence or absence of a gestational sac (defined as a cystic structure surrounded by a uniform rind of solid tissue) or embryonic elements (yolk sac or an embryo) were recorded. Color Doppler sonography was performed on this extraovarian adnexal mass. Color vascularity of the extraovarian adnexal mass was assessed with the machine setting at the highest sensitivity (3 cm/sec). Color vascularity of the extraovarian adnexal mass was graded subjectively on a scale from 0 to 3 (grade 0 = no vascularity, grade 1 = vascularity occupying less than one third of the extraovarian adnexal mass, grade 2 = vascularity occupying less than two thirds of the extraovarian adnexal mass, and grade 3 = vascularity occupying more than two thirds of the extraovarian adnexal mass). The lowest resistive index and the highest peak systolic velocity were measured in the extraovarian adnexal mass. We used color Doppler sonography as a road map to measure the Doppler indexes. Using color mapping, we obtained a minimum of three measurements of the lowest resistive index and the highest peak systolic velocity, generally from the zones of high velocity. Therefore, the Doppler indexes were not measured if the extraovarian adnexal mass was avascular on color Doppler sonography.

We reviewed patients' charts to determine the final clinical outcome of their pregnancy (i.e., expectant treatment or medical or surgical treatment). We did not obtain ethics approval because the sonography examination and the data obtained were part of our routine data collection in the evaluation of patients with suspected ectopic pregnancies.

Continuous variables were calculated as the mean value plus or minus the standard deviation (SD); categorical variables were calculated as a percentage. Comparisons between the two groups were made: in categorical data using the Fisher's exact test or the chisquare test and in continuous data using the Student's t test or the Mann-Whitney test. Multivariate logistic regression analysis was used to identify predictors of the outcome of ectopic pregnancy (variables with a p value < 0.05 by univariate analysis were entered into the multivariate analysis). A p value less than 0.05 was considered significant. The independent variables (potential clinical and sonographic predictors) evaluated included the initial ß-hCG level, patient's age, last menstrual period at the time of presentation, ectopic pregnancy size, the presence of a gestational sac, the presence of embryonic elements, the degree of vascularity, and the resistive index and peak systolic velocity of the ectopic pregnancy. The dependent variable was the final outcome. The continuous independent variables were dichotomized at the median value. The time from the last menstrual period values were dichotomized at 6.5 weeks, ß-hCG levels at 864 IU/L, and resistive index at 0.61. Statistical analysis was performed with GB-Stat version 6.5 (Dynamic Microsystems, Silver Spring, MD) and SPSS for Windows, version 9.0 (Statistical Package for the Social Sciences, Chicago, IL).


Results
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 Abstract
 Introduction
 Subjects and Methods
 Results
Discussion
 References
 
An extraovarian predominantly solid adnexal mass was identified in every patient. Of 78 patients with ectopic pregnancies, 46 had declining ß-hCG levels, and 32 ectopic pregnancies were live (n = 4) or had steady (n = 8) or rising (n = 20) ß-hCG levels. Of 46 patients with ectopic pregnancies and declining ß-hCG levels, 31 spontaneously resolved and 15 underwent surgery. The indications for surgery were patient's preference (n = 4), increasing pain (n = 5), enlarging ectopic pregnancy on transvaginal sonography (n = 1), increasing fluid on transvaginal sonography (n = 1), or an associated complex ovarian mass with nonspecific solid components (n = 1) that was confirmed to be an ovarian dermoid cyst with thyroid elements at surgery. In the remaining three patients, the reason for surgery was not mentioned. In the group that underwent surgery despite declining ß-hCG levels, only one ectopic pregnancy was ruptured. The data were analyzed twice using either ß-hCG trend or the final treatment as the outcome. In the first analyzed group, there were 78 patients (comparing those with declining ß-hCG levels [n = 46] with those with steady or rising ß-hCG levels [n = 32]). In the second analyzed group, there were 63 patients (comparing those with expectant treatment [n = 31] with those who underwent medical or surgical treatment because of steady or rising ß-hCG levels [n = 32]). In the latter analysis, the patients included were those whose treatment was based on the ß-hCG trend; therefore, there was no bias related to the patient's or surgeon's preference of treatment.

The group with declining ß-hCG levels and the group with steady or rising ß-hCG levels were compared in a univariate analysis (Table 2). Thirty-nine (85%) of 46 ectopic pregnancies in the group with declining ß-hCG levels were vascular compared with 28 (88%) of 32 pregnancies in the group with rising or plateaued ß-hCG levels (p > 0.05). There was a significant difference between the two groups with respect to the time interval from the last menstrual period at the time of presentation, the initial ß-hCG levels, and the presence of a gestational sac at the time of presentation (p < 0.05). The group with rising ß-hCG levels had shorter time intervals from their last menstrual period and higher ß-hCG levels at the time of presentation. Ectopic pregnancies with a gestational sac were more likely to have rising or steady ß-hCG levels. Lower resistive indexes of ectopic pregnancy were of borderline significance (p = 0.05) to predict rising or steady ß-hCG trends.


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  		TABLE 2 Comparison of Group with Declining and Group with Steady or Rising Serum ß-hCG

 

Comparing the group that was treated expectantly with the group that underwent medical or surgical treatment because of steady or rising ß-hCG levels (Table 3), the results were similar. Twenty-four (77%) of 31 ectopic pregnancies in the group with declining ß-hCG levels were vascular compared with 28 (88%) of 32 pregnancies in the group with rising or plateaued ß-hCG levels (p > 0.05). A longer time interval from the last menstrual period (older ectopic pregnancies), lower ß-hCG levels at presentation, and the absence of a gestational sac predicted expectant treatment (p < 0.05). Higher extraovarian adnexal mass resistive indexes predicted expectant treatment with borderline statistical significance (p = 0.07). Multiple logistic regression was performed in this group because the final treatment was based on the ß-hCG trend. The final model with the statistically significant independent predictors for spontaneous resolution is outlined in Table 4. This final model confirms that time interval from the last menstrual period, ß-hCG level at the time of presentation, and the presence of a gestational sac are strong independent predictors of the final treatment outcome (p < 0.05). Resistive index was of borderline significance (p = 0.09). This finding may be related to the small sample size as suggested by the higher p value in the univariate analysis in the smaller group of patients with the final treatment used as the end point of the study (Tables 2 and 3). Odds ratios less than one and negative parameter estimates indicate that lower values of ß-hCG and the absence of a gestational sac are independent predictors of spontaneously resolving ectopic pregnancies. Odds ratios greater than one and positive values of parameter estimates indicate that higher values of the last menstrual period and the resistive index are independent predictors of spontaneously resolving ectopic pregnancies.


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  		TABLE 3 Comparison of Group with Expectant Management and Group Undergoing Medical or Surgical Treatment for Steady or Rising Serum ß-hCG Levels

 

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  		TABLE 4 Final Model: Predictors of Spontaneous Resolution of Ectopic Pregnancy

 

Patient's age, ectopic pregnancy size, the presence of embryonal elements, vascularity, and peak systolic velocity of the extraovarian adnexal mass did not predict the outcome of the pregnancy (p > 0.05).


Discussion
Top
 Abstract
 Introduction
 Subjects and Methods
 Results
 Discussion
References
 
Recognition of the spontaneous resolution of an ectopic pregnancy dates back to the original report of Lund [5] published in 1955. Stable minimally symptomatic and asymptomatic patients with a positive pregnancy test and negative findings on transvaginal sonography can be followed up by measuring their quantitative ß-hCG level [17, 25, 26]. Patients with declining ß-hCG levels are considered to have trophoblast in regression (which includes both ectopic and failing intrauterine pregnancies) and are treated expectantly, and those with rising ß-hCG levels undergo further investigation. Follow-up sonography is performed in the latter group if the initial ß-hCG level is below a discriminatory level of 1000 IU/L (second international standard) [27], which is equivalent to the 2200 third international standard. In stable patients, an algorithm based on the follow-up ß-hCG level and transvaginal sonography will reduce the number of invasive procedures (i.e., diagnostic laparoscopy and dilatation and curettage) [28]. In the literature, the reported percentages of ectopic pregnancies that spontaneously resolve vary from 4.9% to 24% [13, 15, 20, 29, 30]. The percentage of ectopic pregnancies selected for expectant treatment because of declining ß-hCG levels that successfully resolve range from 47.7% [20] to 73% [19] [13, 17,18,19,20, 26, 29, 30]. Some ectopic pregnancies that are considered for expectant treatment on the basis of a drop in the patient's ß-hCG level require treatment because of a subsequent increase in ß-hCG level or increasing symptoms. Additionally, there is a potential for rupture of ectopic pregnancy during follow-up, although it is rare [31]. Therefore, it is useful to offer the clinician and the patient additional predictors of spontaneous resolution.

In this study, we analyzed our data on both the basis of ß-hCG trends and the final treatment as the outcome. Treatment was used as the gold standard for outcome. However, for the treatment outcome, we considered only patients who had their treatments based on ß-hCG trends because some patients' treatments were based on the physicians' or patients' preference or patients' symptoms.

In our study, a lower initial ß-hCG level was a significant predictor of the spontaneous resolution of ectopic pregnancy. This is in agreement with previous reports [15, 19, 29, 30]. Among patients with spontaneous resolution of ectopic pregnancy, a ß-hCG level less than 1000 IU/L was present in 88% [19] and 96% [29] of patients and a ß-hCG level less than 200 IU/L was present in 88% of patients in another series [30]. Additionally, a rapidly decreasing ß-hCG level predicts a favorable outcome [19, 30]. Although the latter remains the most significant predictor of spontaneous resolution, it requires serial ß-hCG level determination. Therefore, it is important to search for predictors of spontaneous resolution that can be used at the time of presentation.

In our series, the lack of a gestational sac on initial sonography increased the odds of the spontaneous resolution of ectopic pregnancy by 5.6 times. This finding has previously been reported in smaller series [15, 19]. Our results show that a longer time interval from the last menstrual period at the time of presentation predicts the spontaneous resolution of ectopic pregnancy. Ectopic pregnancies with the last menstrual period exceeding 6.5 weeks are 7.4 times more likely to spontaneously resolve. To our knowledge, this finding has not been previously reported; however, in one series [16], 42% of ectopic pregnancies with a low initial ß-hCG level spontaneously resolved, despite initially rising ß-hCG levels. This finding may also suggest that ectopic pregnancies detected or presenting later are more likely to resolve spontaneously. We do not have an explanation for this finding but we postulate that it may be a self-selection phenomenon in that the ectopic pregnancies that are not treated early may outgrow their blood supply.

A high resistive index reached borderline significance as a predictor of spontaneous resolution. Ectopic pregnancies with a resistive index greater than 0.61 were 1.3 times more likely to spontaneously resolve. Although, in general, spontaneously resolving ectopic pregnancies were less vascular than ectopic pregnancies requiring treatment, the difference was not statistically significant. This may be caused by the subjective nature of the degree of vascularity assessment in our study. In general, less vascular ectopic pregnancies show higher impedance flow. Therefore, the detection of flow on the avascular (on the basis of color Doppler sonography) ectopic pregnancies would have likely shifted the mean resistive index to the higher values in spontaneously resolving ectopic pregnancies.

In our study, the initial size of an ectopic pregnancy did not appear to differ significantly between the resolved ectopic pregnancies and those requiring further treatment. However, decreasing size of ectopic pregnancy during follow-up on transvaginal sonography had a sensitivity of 84% and a specificity of 100% to predict spontaneous resolution in a series reported by Cacciatore et al. [18].

There were some limitations in our study. In ectopic pregnancies with expectant treatment, we did not have surgical proof of ectopic pregnancy. Therefore, some ectopic pregnancies that spontaneously resolved could have theoretically represented a failed intrauterine pregnancy with trophoblast in regression. Considering the reportedly high specificity of an extraovarian adnexal mass to diagnose ectopic pregnancy [3, 4], this is probably a rare phenomenon. Although consecutive patients with ectopic pregnancy and follow-up ß-hCG level monitoring were included, there is a potential for selection bias because we had to eliminate some ectopic pregnancies that were treated immediately after diagnosis; therefore, the true final outcome for these pregnancies was not available. However, there was no significant difference between the study group and the group that was eliminated with respect to ß-hCG levels, which are good indicators of how advanced the ectopic pregnancy is. The other limitation of this study is the subjective assessment of vascularity on color Doppler sonography. This assessment depends on the sensitivity of the Doppler equipment and is also a subjective measure of blood flow as compared with looking at the perfusion of ectopic pregnancy, which is more objective. This may explain why our results do not show vascularity as a predictor variable.

In conclusion, the absence of a gestational sac, lower ß-hCG levels at presentation, longer time intervals from the last menstrual period, and higher resistive indexes of ectopic pregnancy appear to be independent predictors of the spontaneous resolution of ectopic pregnancy.


Acknowledgments
 
We thank Robert Platt, Department of Epidemiology and Biostatistics of McGill University, for his assistance with statistical analysis, and Heidi Van Alstyne for preparation of the manuscript.


References
Top
 Abstract
 Introduction
 Subjects and Methods
 Results
 Discussion
 References
 

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