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Failed Tubal Sterilization as An Etiologic Factor in Ectopic Tubal Pregnancy
FERTILITY AND STERILITY Copyright '
Vol.
1978 The American Fertility Society
29, No.5, May 1978 Printed in V.SA.
FAILED TUBAL STERILIZATION AS AN ETIOLOGIC FACTOR IN ECTOPIC TUBAL PREGNANCY
LOUIS H. HONORE, F.R.C.P.(C)* KATHLEEN E. O'HARA, F.R.C.P.(C)
Division of Laboratories, Grace General Hospital, and Division of Pathology, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
An indirect statistical method was used to demonstrate that failed tubal sterilization must be considered as a significant etiologic factor in tubal ectopic pregnancy. Since the exact incidence of poststerilization pregnancies was unknown in our population, a "theoretical" incidence of a 0.71% failure rate was used as the most realistic estimate on the basis of published reports of failed tubal sterilizations. From this figure the "expected" number of poststerilization conceptions, both total and tubal, was computed. The observed incidence of poststerilization ectopic tubal pregnancy was found to be 20 times the "expected" incidence in our population.
Failed tubal sterilization is now recognized as an increasingly important factor in the etiology of ectopic tubal pregnancy.I-3 The evidence is based not only on case reports4, 5 but also on more extensive studies demonstrating an unusually high incidence of previous tubal ligation in series of tubal ectopic pregnancy.6-8 This subject has recently been reviewed. 9 We present further statistical evidence to support the etiologic significance of failed tubal sterilization in ectopic tubal pregnancy. Ideally, the total number of conceptions after tubal sterilization, including live births, stillbirths, spontaneous or therapeutic abortions, ectopic pregnancies, and trophoblastic neoplasms, should be known in the population investigated. From the known incidence of ectopic pregnancy in that particular population, the expected incidence of tubal ectopic pregnancy after tubal sterilization could be derived and compared directly with the observed incidence. This comparison would provide direct support for, or evidence against, tubal sterilization as a significant etiologic factor in tubal ectopic pregnancy. However, this ideal
situation may be difficult to achieve, if not impossible, because unbiased follow-up of women tub ally sterilized by a single institution is likely to run into a host of problems such as patient migration, change of address or name, and poor response by the women to mailed questionnaires,7 For this reason, an indirect statistical approach was used to avoid the follow-up problem. The total number of conceptions, including live births, stillbirths, spontaneous abortions (therapeutic abortions are not performed), ectopic pregnancies, and hydatidiform moles, recorded at the Grace General Hospital from 1970 through 1976 was obtained from medical records; the incidence of ectopic pregnancy in this population was then calculated. The total number of tubal sterilizations performed at the same hospital from 1970 to mid-1977 was also obtained, and from this figure an "expected" number of conceptions after tubal sterilization was computed, using the figure 0.71% as the most realistic estimate of poststerilization failure rate. 10 With the exception of the report by Uchida,ll who recorded no failure after 5000 tubal sterilizations, all other reports mentioned failure rates of 0.1% to 1.7%.7,12.13 Because the study by Garb,IO who reported the 0.71% failure rate, was based on a very large series of patients subjected to many forms of tubal sterilization, we considered this value to be the
Received October 10, 1977; revised December 29, 1977; accepted January 2, 1978. *Reprint requests: Dr. Louis H. Honore, Department of Laboratories, Grace General Hospital, 241 LeMarchant Road, St. John's, Newfoundland AlE 1P9, Canada.
509
510
HONORE AND O'HARA
closest estimate of the unknown poststerilization failure rate in our population. MATERIALS AND METHODS
The total number of conceptions from 1970 through 1976 was determined, including all live births, stillbirths, spontaneous abortions, ectopic pregnancies, and hydatidiform molar pregnancies. All cases of ectopic tubal pregnancy from 1970 to mid-1977 were recorded, and the authors, who had personally examined 17 cases, reviewed the pathology slides of 10 other cases in which some doubt existed regarding the diagnosis. The total number of tubal sterilizations performed from 1970 to mid-1977, either postpartum or as interval procedures, was determined; the tubal specimens, consisting of material obtained by distal salpingectomy and of ampullary segments excised by the Pomeroy technique, were not examined pathologically with the exception of specimens from 1017 cases personally studied by the authors.
May 1978
TABLE 2. "Expected" and Actual Poststerilization Ectopic Tubal Pregnancies (1970 to Mid-1977) Total no. of sterilizations "Expected" no. of pregnancies after tubal pregnancies "Expected" no. of poststerilization ectopic tubal pregnancies Observed no. of poststerilization ectopic tubal pregnancies
5238.00 37.19 0.10 2.00
sterilization tubal pregnancies was computed as 0.10; the observed number of such ectopic pregnancies, recorded over the same period, was 2. The difference between the "expected" and observed values, i.e., 20 times, was highly significant. It was recognized that an unknown number of women who had left the area might have had poststerilization ectopic pregnancies treated elsewhere and not recorded at our hospital. In other words, these two ectopic pregnancies constituted the minimal number of such pregnancies that could have occurred in that population of patients subjected to tubal sterilization. DISCUSSION
RESULTS
The total number of conceptions, including live births, stillbirths, spontaneous abortions, ectopic pregnancies, and hydatidiform molar pregnancies, is given in Table 1 with the incidence of each type of pregnancy in terms of the total number of recorded pregnancies. Table 2 includes the number of tubal sterilizations, the "expected" ~umber of all forms of poststerilization conceptIons, the "expected" number of poststerilization tubal ectopic pregnancies, and the observed number of tubal ectopic pregnancies. By using the 0.71% failure rate 10 as a realistic estimate of the unknown failure rate in our population, the "expected" number of conceptions following tubal sterilization was calculated as 37.19. By using the incidence of 0.27% for tubal ectopic pregnancy in our population, the "expected" number of postTABLE 1. Total Number of Pregnancies during 1970-1976, Including Live Births, Stillbirths, Spontaneous Abortions, and Ectopic Pregnancies Type of pregnancy
No. of pregnancies
% Incidence in terms
oftotai no. of pregnancies
Live birth Stillbirth Spontaneous abortion Ectopic pregnancy (including 1 ovarian pregnancy) Hydatidiform mole
19,201 257 2,048 58
88.98 1.19 9.49 0.27
14
0.07
Total
21,578
100.00
With this indirect statistical method, our results show that the observed incidence of ectopic tubal pregnancy after tubal sterilization is at least 20 times the "expected" incidence in our population. This indirect approach was used because it depended on reliable statistics obtained from one hospital and avoided the use of systematic followup. Given the present mobility of patients, the number of remarriages, and the easy accessibility of any hospital to any patient under the existing ?ea~th-~are system, it is doubtful whether any ~nstItutIon can obtain accurate follow-up data on Its cases of tubal sterilization. The only way of achieving such an ideal may well be the establishment of a tubal sterilization registry. The occurrence of pregnancy after tubal sterilization has been clearly established, but the exact mechanisms underlying this unexpected developmentare still poorly documented. Ligation of the round ligament instead of the tube has been implicated,14 but this technical error must be of trivial significance, as it is not usually mentioned by later writers and the senior author has seen only one case in which the round ligament was mistaken for the tube in well over 3000 sterilizations personally studied. The most important factor is not generally considered to be recanalization, which re-establishes continuity between the severed tubal segments or leads to the reconstitution of an "ostium" at the terminal end of the
Vol. 29, No.5
ECTOPIC PREGNANCY AFTER TIJBAL STERll..IZATION
residual tube. This recanalization process has been fully documented pathologically in one case. 15 The abnormal reconstitution of the tubal lumen, with the formation of blind pouches and slitlike spaces, probably underlies the greater tendency for the development of ectopic tubal pregnancy when conception occurs after tubal sterilization. As was stressed by Woodruff and Pauerstein,16 the only surgical procedure which guarantees absolute sterility in the female is bilateral oophorectomy with or without removal of the internal genitalia, as even simple hysterectomy with adnexal ablation can be associated with abdominal pregnancy. The incidence of tubal sterilization is increasing worldwide, largely because of the problems encountered with other forms of nonmechanical, mechanical, and pharmacologic contraception. As a result, there will be an increase in poststerilization conceptions and, de facto, of unexpected ectopic tubal pregnancies. All clinicians must therefore be aware of the possibility of ectopic tubal pregnancy when confronted with an acute abdomen, subacute or chronic lower abdominal pain, and abnormal vaginal bleeding in a young woman. Failure to diagnose ectopic pregnancy in the patient with a history of tubal sterilization may have catastrophic results. 17
REFERENCES 1. Beral V: An epidemiological study of recent trends in ectopic pregnancy. Br J Obstet Gynaecol 82:775, 1975
511
2. McElin TW, Iffy L: Ectopic gestation: a consideration of new and controversial issues relating to pathogenesis and management. Obstet Gyencol Annu 5:241, 1976 3. Weekes AR Hutchins CJ: Ectopic pregnancy: a five-year review. Br J Clin Pract 30:104, 1976 4. Sivanesaratnam V, Ng KH: Tubal pregnancies following postpartum sterilization. Fertil Steril 26:945, 1975 5. Sneik HH, Yussman MA: Ruptured ectopic pregnancy after bilateral laparascopic tubal ligation. Am J Obstet Gynecol 125:569, 1976 6. Wacek A, Glattharr E: Uber sterilisations-versager. Zentralbl Gynaekol 87:821, 1965 7. White CA: Tubal sterilization: a fIfteen-year survey. Am J Obstet GynecoI95:31, 1966 8. Chakravarti S, Shardlow J: Tubal pregnancy after sterilization. Br J Obstet GynaecoI82:58, 1975 9. Tatum HJ, Schmidt FH: Contraceptive and sterilization practices and extrauterine pregnancy: a realistic perspective. Fertil Steril 28:407, 1977 10. Garb AE: A review of tubal sterilization failures. Obstet Gynecol Survey 12:291, 1957 11. Uchida H: Uchida's abdominal sterilization technique. In Proceedings of the Third World Congress on Obstetrics and Gynecology, Vol 1. Vienna, Wiener Medizinische Akademie fUr Artzleiche Fortbildung, 1961, p 26 12. Prystowsky H, Eastman- NJ: PUerperaf tubal sterilization. Report of 1830 cases. JAMA 148:463, 1955 13. Paniagua ME, Tayback M, Janer JL, Vazquez JL: Medical and- psychological sequelae of surgical sterilization of women. Am J Obstet Gynecol 90:421, 1964 14. Dieckmann WJ, Hauser EB: Pregnancy following tubal sterilization. Am J Obstet Gynecol 55:308,' 1948 15. Hernandez FJ: Tubal ligation and pregnancy: mechanism of recanalization after tubal ligation. Fertil SteriI26:393, 1975 16. Woodruff A, Pauerstein CJ: The Fallopian Tube. Baltimore, Williams & Williams Co, 1969, p 341 17. Benedet JL, Thomas WDS, Ho-Yuen B: An analysis of maternal deaths in British Columbia, 1963-1970. Can Med Assoc J 110:783, 1974
Vol.
1978 The American Fertility Society
29, No.5, May 1978 Printed in V.SA.
FAILED TUBAL STERILIZATION AS AN ETIOLOGIC FACTOR IN ECTOPIC TUBAL PREGNANCY
LOUIS H. HONORE, F.R.C.P.(C)* KATHLEEN E. O'HARA, F.R.C.P.(C)
Division of Laboratories, Grace General Hospital, and Division of Pathology, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
An indirect statistical method was used to demonstrate that failed tubal sterilization must be considered as a significant etiologic factor in tubal ectopic pregnancy. Since the exact incidence of poststerilization pregnancies was unknown in our population, a "theoretical" incidence of a 0.71% failure rate was used as the most realistic estimate on the basis of published reports of failed tubal sterilizations. From this figure the "expected" number of poststerilization conceptions, both total and tubal, was computed. The observed incidence of poststerilization ectopic tubal pregnancy was found to be 20 times the "expected" incidence in our population.
Failed tubal sterilization is now recognized as an increasingly important factor in the etiology of ectopic tubal pregnancy.I-3 The evidence is based not only on case reports4, 5 but also on more extensive studies demonstrating an unusually high incidence of previous tubal ligation in series of tubal ectopic pregnancy.6-8 This subject has recently been reviewed. 9 We present further statistical evidence to support the etiologic significance of failed tubal sterilization in ectopic tubal pregnancy. Ideally, the total number of conceptions after tubal sterilization, including live births, stillbirths, spontaneous or therapeutic abortions, ectopic pregnancies, and trophoblastic neoplasms, should be known in the population investigated. From the known incidence of ectopic pregnancy in that particular population, the expected incidence of tubal ectopic pregnancy after tubal sterilization could be derived and compared directly with the observed incidence. This comparison would provide direct support for, or evidence against, tubal sterilization as a significant etiologic factor in tubal ectopic pregnancy. However, this ideal
situation may be difficult to achieve, if not impossible, because unbiased follow-up of women tub ally sterilized by a single institution is likely to run into a host of problems such as patient migration, change of address or name, and poor response by the women to mailed questionnaires,7 For this reason, an indirect statistical approach was used to avoid the follow-up problem. The total number of conceptions, including live births, stillbirths, spontaneous abortions (therapeutic abortions are not performed), ectopic pregnancies, and hydatidiform moles, recorded at the Grace General Hospital from 1970 through 1976 was obtained from medical records; the incidence of ectopic pregnancy in this population was then calculated. The total number of tubal sterilizations performed at the same hospital from 1970 to mid-1977 was also obtained, and from this figure an "expected" number of conceptions after tubal sterilization was computed, using the figure 0.71% as the most realistic estimate of poststerilization failure rate. 10 With the exception of the report by Uchida,ll who recorded no failure after 5000 tubal sterilizations, all other reports mentioned failure rates of 0.1% to 1.7%.7,12.13 Because the study by Garb,IO who reported the 0.71% failure rate, was based on a very large series of patients subjected to many forms of tubal sterilization, we considered this value to be the
Received October 10, 1977; revised December 29, 1977; accepted January 2, 1978. *Reprint requests: Dr. Louis H. Honore, Department of Laboratories, Grace General Hospital, 241 LeMarchant Road, St. John's, Newfoundland AlE 1P9, Canada.
509
510
HONORE AND O'HARA
closest estimate of the unknown poststerilization failure rate in our population. MATERIALS AND METHODS
The total number of conceptions from 1970 through 1976 was determined, including all live births, stillbirths, spontaneous abortions, ectopic pregnancies, and hydatidiform molar pregnancies. All cases of ectopic tubal pregnancy from 1970 to mid-1977 were recorded, and the authors, who had personally examined 17 cases, reviewed the pathology slides of 10 other cases in which some doubt existed regarding the diagnosis. The total number of tubal sterilizations performed from 1970 to mid-1977, either postpartum or as interval procedures, was determined; the tubal specimens, consisting of material obtained by distal salpingectomy and of ampullary segments excised by the Pomeroy technique, were not examined pathologically with the exception of specimens from 1017 cases personally studied by the authors.
May 1978
TABLE 2. "Expected" and Actual Poststerilization Ectopic Tubal Pregnancies (1970 to Mid-1977) Total no. of sterilizations "Expected" no. of pregnancies after tubal pregnancies "Expected" no. of poststerilization ectopic tubal pregnancies Observed no. of poststerilization ectopic tubal pregnancies
5238.00 37.19 0.10 2.00
sterilization tubal pregnancies was computed as 0.10; the observed number of such ectopic pregnancies, recorded over the same period, was 2. The difference between the "expected" and observed values, i.e., 20 times, was highly significant. It was recognized that an unknown number of women who had left the area might have had poststerilization ectopic pregnancies treated elsewhere and not recorded at our hospital. In other words, these two ectopic pregnancies constituted the minimal number of such pregnancies that could have occurred in that population of patients subjected to tubal sterilization. DISCUSSION
RESULTS
The total number of conceptions, including live births, stillbirths, spontaneous abortions, ectopic pregnancies, and hydatidiform molar pregnancies, is given in Table 1 with the incidence of each type of pregnancy in terms of the total number of recorded pregnancies. Table 2 includes the number of tubal sterilizations, the "expected" ~umber of all forms of poststerilization conceptIons, the "expected" number of poststerilization tubal ectopic pregnancies, and the observed number of tubal ectopic pregnancies. By using the 0.71% failure rate 10 as a realistic estimate of the unknown failure rate in our population, the "expected" number of conceptions following tubal sterilization was calculated as 37.19. By using the incidence of 0.27% for tubal ectopic pregnancy in our population, the "expected" number of postTABLE 1. Total Number of Pregnancies during 1970-1976, Including Live Births, Stillbirths, Spontaneous Abortions, and Ectopic Pregnancies Type of pregnancy
No. of pregnancies
% Incidence in terms
oftotai no. of pregnancies
Live birth Stillbirth Spontaneous abortion Ectopic pregnancy (including 1 ovarian pregnancy) Hydatidiform mole
19,201 257 2,048 58
88.98 1.19 9.49 0.27
14
0.07
Total
21,578
100.00
With this indirect statistical method, our results show that the observed incidence of ectopic tubal pregnancy after tubal sterilization is at least 20 times the "expected" incidence in our population. This indirect approach was used because it depended on reliable statistics obtained from one hospital and avoided the use of systematic followup. Given the present mobility of patients, the number of remarriages, and the easy accessibility of any hospital to any patient under the existing ?ea~th-~are system, it is doubtful whether any ~nstItutIon can obtain accurate follow-up data on Its cases of tubal sterilization. The only way of achieving such an ideal may well be the establishment of a tubal sterilization registry. The occurrence of pregnancy after tubal sterilization has been clearly established, but the exact mechanisms underlying this unexpected developmentare still poorly documented. Ligation of the round ligament instead of the tube has been implicated,14 but this technical error must be of trivial significance, as it is not usually mentioned by later writers and the senior author has seen only one case in which the round ligament was mistaken for the tube in well over 3000 sterilizations personally studied. The most important factor is not generally considered to be recanalization, which re-establishes continuity between the severed tubal segments or leads to the reconstitution of an "ostium" at the terminal end of the
Vol. 29, No.5
ECTOPIC PREGNANCY AFTER TIJBAL STERll..IZATION
residual tube. This recanalization process has been fully documented pathologically in one case. 15 The abnormal reconstitution of the tubal lumen, with the formation of blind pouches and slitlike spaces, probably underlies the greater tendency for the development of ectopic tubal pregnancy when conception occurs after tubal sterilization. As was stressed by Woodruff and Pauerstein,16 the only surgical procedure which guarantees absolute sterility in the female is bilateral oophorectomy with or without removal of the internal genitalia, as even simple hysterectomy with adnexal ablation can be associated with abdominal pregnancy. The incidence of tubal sterilization is increasing worldwide, largely because of the problems encountered with other forms of nonmechanical, mechanical, and pharmacologic contraception. As a result, there will be an increase in poststerilization conceptions and, de facto, of unexpected ectopic tubal pregnancies. All clinicians must therefore be aware of the possibility of ectopic tubal pregnancy when confronted with an acute abdomen, subacute or chronic lower abdominal pain, and abnormal vaginal bleeding in a young woman. Failure to diagnose ectopic pregnancy in the patient with a history of tubal sterilization may have catastrophic results. 17
REFERENCES 1. Beral V: An epidemiological study of recent trends in ectopic pregnancy. Br J Obstet Gynaecol 82:775, 1975
511
2. McElin TW, Iffy L: Ectopic gestation: a consideration of new and controversial issues relating to pathogenesis and management. Obstet Gyencol Annu 5:241, 1976 3. Weekes AR Hutchins CJ: Ectopic pregnancy: a five-year review. Br J Clin Pract 30:104, 1976 4. Sivanesaratnam V, Ng KH: Tubal pregnancies following postpartum sterilization. Fertil Steril 26:945, 1975 5. Sneik HH, Yussman MA: Ruptured ectopic pregnancy after bilateral laparascopic tubal ligation. Am J Obstet Gynecol 125:569, 1976 6. Wacek A, Glattharr E: Uber sterilisations-versager. Zentralbl Gynaekol 87:821, 1965 7. White CA: Tubal sterilization: a fIfteen-year survey. Am J Obstet GynecoI95:31, 1966 8. Chakravarti S, Shardlow J: Tubal pregnancy after sterilization. Br J Obstet GynaecoI82:58, 1975 9. Tatum HJ, Schmidt FH: Contraceptive and sterilization practices and extrauterine pregnancy: a realistic perspective. Fertil Steril 28:407, 1977 10. Garb AE: A review of tubal sterilization failures. Obstet Gynecol Survey 12:291, 1957 11. Uchida H: Uchida's abdominal sterilization technique. In Proceedings of the Third World Congress on Obstetrics and Gynecology, Vol 1. Vienna, Wiener Medizinische Akademie fUr Artzleiche Fortbildung, 1961, p 26 12. Prystowsky H, Eastman- NJ: PUerperaf tubal sterilization. Report of 1830 cases. JAMA 148:463, 1955 13. Paniagua ME, Tayback M, Janer JL, Vazquez JL: Medical and- psychological sequelae of surgical sterilization of women. Am J Obstet Gynecol 90:421, 1964 14. Dieckmann WJ, Hauser EB: Pregnancy following tubal sterilization. Am J Obstet Gynecol 55:308,' 1948 15. Hernandez FJ: Tubal ligation and pregnancy: mechanism of recanalization after tubal ligation. Fertil SteriI26:393, 1975 16. Woodruff A, Pauerstein CJ: The Fallopian Tube. Baltimore, Williams & Williams Co, 1969, p 341 17. Benedet JL, Thomas WDS, Ho-Yuen B: An analysis of maternal deaths in British Columbia, 1963-1970. Can Med Assoc J 110:783, 1974