- Email: [email protected]
Is Rh immune globulin needed in early first-trimester abortion? A review
CLINICAL OPINION
Is Rh immune globulin needed in early first-trimester abortion? A review Sami Jabara, MD, and Kurt T. Barnhart, MD MSCE Philadelphia, Pa The prophylactic use of Rh immune globulin has been a medical success, protecting women who could be at risk from exposure to the Rh(D) antigen. Thus, it is not surprising that Rh(D) immunoprophylaxis has been extended from women with term pregnancies to all women with miscarriages, abortions, and ectopic pregnancies. In this article we review the existing medical literature to assess the risks of fetomaternal hemorrhage and Rh isoimmunization after complications of a first-trimester pregnancy, induced abortion, or ectopic pregnancy. The evidence to support the use of Rh immune globulin in the first trimester is sparse, but there is theoretic evidence of its necessity. Despite weak evidence to support its use, there is little risk. (Am J Obstet Gynecol 2003;188:623-7.)
Key words: Rh immune globulin, first trimester, abortion
An Rh-negative woman may develop isoimmunization on exposure to Rh(D) antigens. Exposure to Rh(D) antigen in future pregnancies may result in Rh(D) immunoglobulin G antibodies that can easily cross the placental-fetal barrier to the fetus, causing complications potentially culminating in fetal anemia, erythroblastosis fetalis, or fetal death. Anti-D immune globulin (Rh immune globulin) can block the primary immune response and thus prevent Rh(D) isoimmunization. The prophylactic use of Rh immune globulin has been a medical success, protecting women who could be at risk from exposure to the Rh(D) antigen. Thus, it is not surprising that Rh(D) immunoprophylaxis has been extended from women with term pregnancies to all women with miscarriages, abortions, and ectopic pregnancies. Has this been a logical extension of good medical practice or an overuse of medical technology in the practice of defensive medicine?
From the Department of Obstetrics and Gynecology, University of Pennsylvania. Received for publication July 22, 2002; revised September 20, 2002; accepted December 3, 2002. Reprint requests: Kurt T. Barnhart, MD, MSCE, Department of Obstetrics and Gynecology, University of Pennsylvania Medical Center, 3400 Spruce St, Dulles 106, Philadelphia, PA 19104. E-mail: [email protected] © 2003, Mosby, Inc. All rights reserved 0002-9378/2003 $30.00 + 0 doi:10.1067/mob.2003.208
The American College of Obstetricians and Gynecologists practice bulletin (Prevention of Rh(D) alloimunization, May 1999)1 states that all unsensitized Rh-negative pregnant women should be given Rh immune globulin within 72 hours of an abortion. No lower limit of gestational age is given as an indication for treatment. The presence of fetal cells in the maternal blood stream at the time of a first-trimester abortion appears to reinforce this action. However, is there substantial evidence to treat women with anti-D immune globulins after early spontaneous or induced abortions? In this article we review the existing medical literature to assess the risks of fetomaternal hemorrhage and Rh(D) isoimmunization after complications of a first-trimester pregnancy, induced abortion, or ectopic pregnancy. To form our opinion, a literature search from 1964 to the present was performed using OVID and PubMed MEDLINE search engines, using the following key words: “rhesus-negative,” “Rh,” “negative,” “isoimmunization,” “Rh immune globulin,” “fetomaternal hemorrhage,” and “alloimmunization.” This search revealed 10 publications. The majority of these publications are case reports and case series, but case-controlled studies and one randomized controlled trial are included (see Table). Reviews, letters to the editor, and expert opinions were not included in this review. The above publications were classified into two categories: evidence supporting and evidence refuting the need for Rh immune globulin administration in early-trimester abortions. 623
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Table. Summary of evaluating the use of Rh immune globulin in women with first-trimester events Author Freda (1964)2 Litwak et al (1970)3 Murray et al (1970)4 Queenan et al (1971)5 Murray and Barron (1972)6 Vissher and Vissher (1972)7 Leong et al (1979)8 Dayton et al 19909 Portney et al (1990)10 Von Stein et al (1992)11
Type Case series Case series Case series Case series Case series RDBCT Case control Case report Case control Case control
Patients NS (mixed) 23 EAb 146 EAb postoperative 98 Sab NS number before and after abortion 38 No Rh immune globulin 75 Eab preop Threatened AB 56 EAb 89 EAb
Controls 0 0 0 0 0 19 received Rh immune globulin 75 Eab postop 0 32 Pregnant controls 94 Pregnant controls
Sensitization defined as positive Coombs’ test. FMH, Fetomaternal hemorrhage defined as positive Kleihauer-Betke test; NS, not specified; ND, not done; Eab, elective abortion; Postop, after curettage; Preop, before curettage; Sab, spontaneous abortion; RDBCT, randomized double-blind controlled trial.
Evidence supporting Rh immune globulin in early-trimester abortions Fetal-maternal transfusion has been demonstrated as early as 5 to 6 weeks of gestation. The mean volume of fetal-maternal transfusion at 8 weeks has been calculated to be 0.33 mL.2 No recent studies have looked at whether those fetal red blood cells (RBC) express the Rh(D) antigen; however, Bergstrom et al12 demonstrated that fetal RBCs can express the Rh(D) antigen as early as 38 days from conception, or 52 days from last menstrual period. The amount of fetal blood needed to cause isoimmunization has been estimated to be 0.25 mL.13 In addition, Rh(D) sensitization has been demonstrated in male volunteers when exposed to as little as 0.1 mL of Rh(D)-positive blood.14 Hence, in theory it is possible that, an “average” fetomaternal transfusion after an abortion at 8 weeks can cause isoimmunization if not treated with Rh immune globulin. Although the calculations above demonstrate the theoretic possibility for isoimmunization, there is limited documentation of the development of Rh(D) antibodies in the first trimester. One reported case series5 followed up 98 Rh-negative patients between 1958 and 1965 who had a spontaneous abortion followed by curettage. Three of these women subsequently had Rh(D) antibodies and they all had gestations greater than 12 weeks by dates. The advanced gestational age of these subjects limits the extrapolation of the true incidence of developing antibodies early in the first trimester. A separate study12 that followed up patients admitted to the Rh clinic between 1960 and 1969 found that the average risk of isoimmunization after abortion is 3%. Details of the clinical course of these subjects were not sufficient to determine a gestational age. It was also not documented whether these cases were spontaneous or elective abortions. An additional report8 evaluated 75 patients undergoing elective abortions at a gestational age of less than 8 weeks as determined by last menstrual period. The
presence of fetal cells in maternal blood was determined by the Kleihauer-Betke test (KB). The background prevalence of a positive KB test in nonbleeding patients before the elective abortion was 2.6%. In this series, a total of 15.5% of women had a positive KB test after the procedure. The number of patients with a positive KB test postoperatively increased with gestational age (9.9% in 5-6 weeks, 16.7% in 6-7 weeks, and 18.6% in 7-8 weeks). Because of the small number of patients in each gestational age group, the number of patients with a positive KB test becomes significantly elevated, compared with the backgrounds level, in gestations greater than 6 to 7 weeks (where the incidence rate is most highly elevated). In a study evaluating women with a threatened abortion,3 11 of 23 patients demonstrated transplacental hemorrhage. In a separate study,6 a fetomaternal hemorrhage of >0.1 mL was reported in 2.9% of women undergoing an elective abortion. The hemorrhage was documented in 1.4% of the women before the abortion was performed and in 1.5% of the women as a result of the procedure. Additional studies9,11 reported that up to 11% of patients with a threatened abortion had a positive KB test compared with 4% in pregnant controls. Many of these studies are limited because those who had fetomaternal hemorrhage, as suggested by a positive KB test, were not followed up to assess development of autoantibodies.3,8,11 One case series4 examined 177 Rhnegative patients undergoing elective abortions, of which 146 had KB tests performed before and after abortion and 96 were followed up with anti-D antibody testing. A total of 44 patients were at <12 weeks of gestation, with no subclassification of gestational age determined. Of the remaining 52 patients, 40 had a gestational age >12 weeks and 12 patients had unspecified gestational ages. Of all women evaluated in this study, seven women (6.2%) had a positive KB test with a fetomaternal hemorrhage of >0.1 mL. However, only two (2% of the total) of these patients
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FMH ND 11/23 Preoperative NS, postoperative 29% ND 1.4% before abortion ND Preop 2.6%, postop 15.5% NA 71 % in Tab, 9.4% in Ctrls 11.2% in Tab, 4.2% in Ctrls
Sensitization
Gestational age
3% ND 2% (+) Coombs, 7% (+) papain 3% 1.5% after abortion 0% in both groups ND 100% ND ND
(with gestational ages of 5 and 8 weeks) became sensitized and had a positive indirect Coombs’ test. Of notable importance is that fetomaternal hemorrhage as determined by the KB test did not correlate with the subsequent development of Rh(D) antibodies (positive Coombs’ test). Both patients who had a positive Coombs’ test had a negative KB test after elective abortion. However, the five other patients who had a significant fetomaternal hemorrhage (>0.1 mL) had Rh(D) antibodies as detected by enzyme (papain)-treated cells, and not by indirect Coombs’ test. The significance of detection of antibodies using the papain methods is not clear. Evidence against Rh immune globulin in earlytrimester abortions A weakness of the evidence supporting the use of Rh immune globulin in the first trimester is its reliance on studies that evaluated fetomaternal hemorrhage (positive KB test) and not the actual development of Rh(D) antibodies. Thus, the true incidence of the development of Rh(D) antibodies in an abnormal first-trimester pregnancy or after elective termination is difficult to determine and remains unknown. A second severe limitation is that many of these studies have no control population or comparison group. These studies need to show a statistically significant increase of the prevalence of fetomaternal hemorrhage relative to normal asymptomatic pregnant patients of the same gestational age to account for the baseline fetomaternal hemorrhage that occurs in the normal population. Interestingly, one study10 noted that transplacental hemorrhage occurred in 7.1% (4/56) of women with a threatened abortion compared with 9.4% (3/32) of pregnant controls). Although not statistically significant, these results contradict the studies that described an increase in the rate of fetomaternal hemorrhage after threatened or elective abortions in the first trimester. A randomized, blinded clinical trial is the most convincing method to determine the true efficacy of a treatment because it reduces bias and confounding. The only randomized double-blind controlled study evaluating the
NS NS 44 <12 wk, 40 >12 wk, 12 NS All >12 wk ND NS 8-16 wk All <8 wk 8 wk 3 d <12 wk <20 wk
benefit of prophylactic Rh immune globulin for Rh(D)negative women with first-trimester pregnancy loss or abortion was performed by Visscher and Visscher7 in 1971. Rh-negative women with Rh-positive fathers undergoing a spontaneous abortion (complete or incomplete) were randomized to receive Rh immune globulin (300 U) or a placebo. A total of 57 women were followed up for 6 months. Nineteen women received Rh immune globulin and 29 received homologous gamma globulin (placebo) and 9 Rh-negative women did not receive any placebo. No patient in either group became immunosensitized. Thus, in the only well-designed trial to evaluate the benefit of Rh immune globulin in the first trimester, the incidence of isoimmunization was zero, with (0/19) or without (0/38) treatment. Critique of the data The data available to make an evidence-based recommendation regarding the utility of Rh immune globulin in the first trimester are extremely limited. Most studies were performed in the early 1970s and were not controlled. In aggregate, these data demonstrate that the number of cases of Rh-negative women who become isoimmunized after pregnancy complications or terminations in the first trimester is very low. The incidence of isoimmunization after a first-trimester abortion ranged from 0% to 3%. Gestational age was uniformly determined by dating from the last menstrual period; ultrasound was not used to confirm dating of the pregnancy. It is, therefore, possible that pregnancies thought to be in the first trimester could actually have been at >12 weeks’ gestation, which would lead to an overestimation of the incidence of immunosensitization in first-trimester abortions. Moreover, many studies evaluated the presence of a positive KB test. The KB test is at best only a surrogate marker of immunosensitization. It has yet to be definitively demonstrated that fetomaternal hemorrhage predictably results in subsequent seroconversion. Only three publications4,7,12 followed up patients for the development of antibodies (Coombs’ test) and not just the presence of fetomaternal hemorrhage (KB test). The only
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randomized, controlled trial evaluating the use of Rh immune globulin in the first trimester demonstrated an incidence of seroconversion of 0%, although this study was small.7 Moreover, the discrepancy in the number of women who received medication or placebo casts doubt as to whether this study was appropriately randomized and blinded. In fact, 9 of 38 women who were in the control group did not even receive a placebo and were followed up as a cohort independently (6 months later) of the other patients. Questions that cannot be addressed on the basis of available data include the distinction between spontaneous and elective instrumental abortion. It is theorized that instrumentation might increase the frequency of immunosensitization.15-19 This question cannot be answered given the published data. There is also no evidence to support or refute the possibility of isoimmunization after diagnosis or treatment of an ectopic pregnancy, chorionic villus sampling, cordocentesis, or amniocentesis. The only reports studying isoimmunization after such procedures examined fetomaternal hemorrhage that was not correlated with isoimmunization and the development of anti-D antibodies.15-19 Another clinical scenario where the use of Rh immune globulin would theoretically not be beneficial is the case of an early spontaneous miscarriage or ectopic pregnancy where the gestational age is greater than 8 weeks by dates (when fetal blood is made), but the embryo has stopped growing at an earlier stage, during which time the Rh(D) antigen is not present on the surface of the RBC (ie, 12 weeks by dates but anembryonic gestation with sac consistent with 6 weeks). There is no evidence to support or refute the use of Rh immune globulin in this scenario. In some situations where the father of the fetus is easily identifiable and is accompanying the patient, testing him for Rh(D) is very helpful in case he is Rh(D) negative.
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domized trial reported in the literature. (For ethical and logistic reasons, this study will most likely never be performed.) Using the scale developed by the US Preventive Services Task force, the quality of evidence to support the use of Rh immune globulin in the first trimester of pregnancy falls into the level III category. This score is the weakest evidence supporting a given practice. Despite the weak evidence to support the use of Rh immune globulin there is little risk involved. The incidence of side effects or complications caused by the use of Rh immune globulin is rare. These risks, compared with the severity of the erythroblastosis fetalis, favor the administration of Rh immune globulin to all unsensitized Rhnegative women undergoing first-trimester abortions (spontaneous or induced) or diagnosed with an ectopic pregnancy. Additionally, there are legal implications to changing what has become a standard of care without compelling evidence. Cost-effectiveness, however, demands that we use the smallest dosage available. The standard of care is to give at least 50 µg of Rh immune globulin intramuscularly to all unsensitized Rh-negative women with an ectopic pregnancy or early-trimester abortion. The 50 µg will provide prophylaxis for a fetomaternal hemorrhage of 2.5 mL,1 which is well beyond the average bleed of 0.33 mL at 8 weeks as calculated.12 KB testing does not correlate with immunosensitization,9 is not cost effective, and should not be used to determine whether Rh immune globulin should be administered. Evidence to support the use of Rh immune globulin after diagnosis and treatment of an ectopic pregnancy is practicality nonexistent. On the basis of the above data, it is possible that treatment is only necessary if the gestational age is greater than 8 weeks from the last menstrual period. Many ectopic pregnancies develop abnormally, and development may lag behind gestational age. A rule of thumb may be to treat only those where fetal cardiac actively is visible on ultrasound examination.
Clinical recommendations Although the evidence to support the use of Rh immune globulin in the first trimester is sparse, there is theoretic evidence of its necessity. Although calculations of the amount of blood necessary to result in immunosensitization are problematic, they do suggest that fetal-maternal hemorrhage in the first trimester is of sufficient volume to potentially cause immunosensitization. Moreover, there have been cases of immunosensitization reported with first-trimester abortions, although the actual incidence is unknown. Additionally, the only randomized trial that has been published is likely underpowered and cannot be considered definitive. If we conservatively estimate the rate of seroconversion to be 2%, a properly designed study with 80% power to determine the efficacy of Rh immune globulin in the first trimester would require a sample size of approximately 100 women per group. This would be at least four times the size of the only ran-
REFERENCES
1. American College of Obstetricians and Gynecologists. Prevention of Rh D isoimmunization. Washington (DC): The College; 1999. Practice bulletin No.: 4. 2. Freda VJ. Recent advances in the Rh problem. Trans N Engl Obstet Gynecol Soc 1964;18:91-104. 3. Litwak O, Taswell H, Banner E, Keith L. Fetal erythrocytes in maternal circulation after spontaneous abortion. JAMA 1970; 215:521-34. 4. Murray S, Barron SL. Transplacental haemorrhage in induced abortion. Lancet 1972;1:954-5. 5. Queenan JT, Kubaryeh SF, Shah S, Holland B. Role of induced abortion in rhesus immunization. Lancet 1971;1:815. 6. Murray S, Barron SL, McNay RA. Transplacental haemorrhage after abortion. Lancet 1970;1:631-4. 7. Visscher RD, Visscher HC. Do Rh-negative women with an early spontaneous abortion need Rh immune prophylaxis? Am J Obstet Gynecol 1972;113:158-65. 8. Leong M, Duby S, Kinch R. Fetal-maternal transfusion following early abortion. Obstet Gynecol 1979;54:424-6.
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9. Dayton VD, Anderson DS, Crosson JT, Cruikshank SH. A case of Rh isoimmunization: should threatened first-trimester abortion be an indication for Rh immune globulin prophylaxis? Am J Obstet Gynecol 1990;163:63-4. 10. Portney DL, Kuller JA, Laifer SA, Rulin MC. Should D immunoglobulin (Rh-immune globulin) be administered to Rhnegative patients with threatened abortions? Proceedings of the annual meeting of the American College of Obstetricians and Gynecologists; 1990 May 5-10; San Francisco, Calif. San Francisco: The College; 1990. p. 19-20. 11. Von Stein GA, Munsick RA, Stiver K, Ryder K. Fetomaternal hemorrhage in threatened abortion. Obstet Gynecol 1992;79:383-6. 12. Bergstrom H, Nilson LA, Nisson L, Ruttinger L. Demonstration of Rh antigens in a 38-day-old fetus. Am J Obstet Gynecol 1967;99:130-3. 13. Mollison PL, Hughes-Jones MC, Lindsay M, Wessely J. Suppression of primary Rh immunization by passively-administered antibody: experiments in volunteers. Vox Sang 1969: 16:421-39.
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14. Zipursky A, Pollock J, Neelands P, Chown B, Israels LG. The transplacental passage of fetal red blood cells and the pathogenesis of Rh immunization during pregnancy. Lancet 1963;2:489-93. 15. Brambati B, Guercilena S, Bonnachi I, Oldrini A, Lanzani A, Piceni L. Feto-maternal transfusion after chorionic villus sampling: clinical implications. Hum Reprod 1986;1:37-40. 16. Blakemore KJ, Baumgarten A, Schoenfeld-Dimaio M, Hobbins JC, Mason EA, Mahoney MJ. Rise in maternal serum α-fetoprotein concentration after chorionic villus sampling and the possibility of isoimmunization. Am J Obstet Gynecol 1986;155:988-93. 17.Blajchman MA, Maudsley RF, Uchida I, Zipursky A. Diagnostic amniocentesis and fetal-maternal bleeding [letter]. Lancet 1974;1:993-4. 18. Daffos F, Capella-Pavlovsky M, Forestier F. Fetal blood sampling during pregnancy with use of a needle guided by ultrasound: a study of 606 consecutive cases. Am J Obstet Gynecol 1985;153:655-60. 19. Pielet BW, Socol ML, MacGregor SN, Ney JA, Dooley SL. Cordocentesis: an appraisal of risks. Am J Obstet Gynecol 1988; 159:1497-500.
Is Rh immune globulin needed in early first-trimester abortion? A review Sami Jabara, MD, and Kurt T. Barnhart, MD MSCE Philadelphia, Pa The prophylactic use of Rh immune globulin has been a medical success, protecting women who could be at risk from exposure to the Rh(D) antigen. Thus, it is not surprising that Rh(D) immunoprophylaxis has been extended from women with term pregnancies to all women with miscarriages, abortions, and ectopic pregnancies. In this article we review the existing medical literature to assess the risks of fetomaternal hemorrhage and Rh isoimmunization after complications of a first-trimester pregnancy, induced abortion, or ectopic pregnancy. The evidence to support the use of Rh immune globulin in the first trimester is sparse, but there is theoretic evidence of its necessity. Despite weak evidence to support its use, there is little risk. (Am J Obstet Gynecol 2003;188:623-7.)
Key words: Rh immune globulin, first trimester, abortion
An Rh-negative woman may develop isoimmunization on exposure to Rh(D) antigens. Exposure to Rh(D) antigen in future pregnancies may result in Rh(D) immunoglobulin G antibodies that can easily cross the placental-fetal barrier to the fetus, causing complications potentially culminating in fetal anemia, erythroblastosis fetalis, or fetal death. Anti-D immune globulin (Rh immune globulin) can block the primary immune response and thus prevent Rh(D) isoimmunization. The prophylactic use of Rh immune globulin has been a medical success, protecting women who could be at risk from exposure to the Rh(D) antigen. Thus, it is not surprising that Rh(D) immunoprophylaxis has been extended from women with term pregnancies to all women with miscarriages, abortions, and ectopic pregnancies. Has this been a logical extension of good medical practice or an overuse of medical technology in the practice of defensive medicine?
From the Department of Obstetrics and Gynecology, University of Pennsylvania. Received for publication July 22, 2002; revised September 20, 2002; accepted December 3, 2002. Reprint requests: Kurt T. Barnhart, MD, MSCE, Department of Obstetrics and Gynecology, University of Pennsylvania Medical Center, 3400 Spruce St, Dulles 106, Philadelphia, PA 19104. E-mail: [email protected] © 2003, Mosby, Inc. All rights reserved 0002-9378/2003 $30.00 + 0 doi:10.1067/mob.2003.208
The American College of Obstetricians and Gynecologists practice bulletin (Prevention of Rh(D) alloimunization, May 1999)1 states that all unsensitized Rh-negative pregnant women should be given Rh immune globulin within 72 hours of an abortion. No lower limit of gestational age is given as an indication for treatment. The presence of fetal cells in the maternal blood stream at the time of a first-trimester abortion appears to reinforce this action. However, is there substantial evidence to treat women with anti-D immune globulins after early spontaneous or induced abortions? In this article we review the existing medical literature to assess the risks of fetomaternal hemorrhage and Rh(D) isoimmunization after complications of a first-trimester pregnancy, induced abortion, or ectopic pregnancy. To form our opinion, a literature search from 1964 to the present was performed using OVID and PubMed MEDLINE search engines, using the following key words: “rhesus-negative,” “Rh,” “negative,” “isoimmunization,” “Rh immune globulin,” “fetomaternal hemorrhage,” and “alloimmunization.” This search revealed 10 publications. The majority of these publications are case reports and case series, but case-controlled studies and one randomized controlled trial are included (see Table). Reviews, letters to the editor, and expert opinions were not included in this review. The above publications were classified into two categories: evidence supporting and evidence refuting the need for Rh immune globulin administration in early-trimester abortions. 623
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Table. Summary of evaluating the use of Rh immune globulin in women with first-trimester events Author Freda (1964)2 Litwak et al (1970)3 Murray et al (1970)4 Queenan et al (1971)5 Murray and Barron (1972)6 Vissher and Vissher (1972)7 Leong et al (1979)8 Dayton et al 19909 Portney et al (1990)10 Von Stein et al (1992)11
Type Case series Case series Case series Case series Case series RDBCT Case control Case report Case control Case control
Patients NS (mixed) 23 EAb 146 EAb postoperative 98 Sab NS number before and after abortion 38 No Rh immune globulin 75 Eab preop Threatened AB 56 EAb 89 EAb
Controls 0 0 0 0 0 19 received Rh immune globulin 75 Eab postop 0 32 Pregnant controls 94 Pregnant controls
Sensitization defined as positive Coombs’ test. FMH, Fetomaternal hemorrhage defined as positive Kleihauer-Betke test; NS, not specified; ND, not done; Eab, elective abortion; Postop, after curettage; Preop, before curettage; Sab, spontaneous abortion; RDBCT, randomized double-blind controlled trial.
Evidence supporting Rh immune globulin in early-trimester abortions Fetal-maternal transfusion has been demonstrated as early as 5 to 6 weeks of gestation. The mean volume of fetal-maternal transfusion at 8 weeks has been calculated to be 0.33 mL.2 No recent studies have looked at whether those fetal red blood cells (RBC) express the Rh(D) antigen; however, Bergstrom et al12 demonstrated that fetal RBCs can express the Rh(D) antigen as early as 38 days from conception, or 52 days from last menstrual period. The amount of fetal blood needed to cause isoimmunization has been estimated to be 0.25 mL.13 In addition, Rh(D) sensitization has been demonstrated in male volunteers when exposed to as little as 0.1 mL of Rh(D)-positive blood.14 Hence, in theory it is possible that, an “average” fetomaternal transfusion after an abortion at 8 weeks can cause isoimmunization if not treated with Rh immune globulin. Although the calculations above demonstrate the theoretic possibility for isoimmunization, there is limited documentation of the development of Rh(D) antibodies in the first trimester. One reported case series5 followed up 98 Rh-negative patients between 1958 and 1965 who had a spontaneous abortion followed by curettage. Three of these women subsequently had Rh(D) antibodies and they all had gestations greater than 12 weeks by dates. The advanced gestational age of these subjects limits the extrapolation of the true incidence of developing antibodies early in the first trimester. A separate study12 that followed up patients admitted to the Rh clinic between 1960 and 1969 found that the average risk of isoimmunization after abortion is 3%. Details of the clinical course of these subjects were not sufficient to determine a gestational age. It was also not documented whether these cases were spontaneous or elective abortions. An additional report8 evaluated 75 patients undergoing elective abortions at a gestational age of less than 8 weeks as determined by last menstrual period. The
presence of fetal cells in maternal blood was determined by the Kleihauer-Betke test (KB). The background prevalence of a positive KB test in nonbleeding patients before the elective abortion was 2.6%. In this series, a total of 15.5% of women had a positive KB test after the procedure. The number of patients with a positive KB test postoperatively increased with gestational age (9.9% in 5-6 weeks, 16.7% in 6-7 weeks, and 18.6% in 7-8 weeks). Because of the small number of patients in each gestational age group, the number of patients with a positive KB test becomes significantly elevated, compared with the backgrounds level, in gestations greater than 6 to 7 weeks (where the incidence rate is most highly elevated). In a study evaluating women with a threatened abortion,3 11 of 23 patients demonstrated transplacental hemorrhage. In a separate study,6 a fetomaternal hemorrhage of >0.1 mL was reported in 2.9% of women undergoing an elective abortion. The hemorrhage was documented in 1.4% of the women before the abortion was performed and in 1.5% of the women as a result of the procedure. Additional studies9,11 reported that up to 11% of patients with a threatened abortion had a positive KB test compared with 4% in pregnant controls. Many of these studies are limited because those who had fetomaternal hemorrhage, as suggested by a positive KB test, were not followed up to assess development of autoantibodies.3,8,11 One case series4 examined 177 Rhnegative patients undergoing elective abortions, of which 146 had KB tests performed before and after abortion and 96 were followed up with anti-D antibody testing. A total of 44 patients were at <12 weeks of gestation, with no subclassification of gestational age determined. Of the remaining 52 patients, 40 had a gestational age >12 weeks and 12 patients had unspecified gestational ages. Of all women evaluated in this study, seven women (6.2%) had a positive KB test with a fetomaternal hemorrhage of >0.1 mL. However, only two (2% of the total) of these patients
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FMH ND 11/23 Preoperative NS, postoperative 29% ND 1.4% before abortion ND Preop 2.6%, postop 15.5% NA 71 % in Tab, 9.4% in Ctrls 11.2% in Tab, 4.2% in Ctrls
Sensitization
Gestational age
3% ND 2% (+) Coombs, 7% (+) papain 3% 1.5% after abortion 0% in both groups ND 100% ND ND
(with gestational ages of 5 and 8 weeks) became sensitized and had a positive indirect Coombs’ test. Of notable importance is that fetomaternal hemorrhage as determined by the KB test did not correlate with the subsequent development of Rh(D) antibodies (positive Coombs’ test). Both patients who had a positive Coombs’ test had a negative KB test after elective abortion. However, the five other patients who had a significant fetomaternal hemorrhage (>0.1 mL) had Rh(D) antibodies as detected by enzyme (papain)-treated cells, and not by indirect Coombs’ test. The significance of detection of antibodies using the papain methods is not clear. Evidence against Rh immune globulin in earlytrimester abortions A weakness of the evidence supporting the use of Rh immune globulin in the first trimester is its reliance on studies that evaluated fetomaternal hemorrhage (positive KB test) and not the actual development of Rh(D) antibodies. Thus, the true incidence of the development of Rh(D) antibodies in an abnormal first-trimester pregnancy or after elective termination is difficult to determine and remains unknown. A second severe limitation is that many of these studies have no control population or comparison group. These studies need to show a statistically significant increase of the prevalence of fetomaternal hemorrhage relative to normal asymptomatic pregnant patients of the same gestational age to account for the baseline fetomaternal hemorrhage that occurs in the normal population. Interestingly, one study10 noted that transplacental hemorrhage occurred in 7.1% (4/56) of women with a threatened abortion compared with 9.4% (3/32) of pregnant controls). Although not statistically significant, these results contradict the studies that described an increase in the rate of fetomaternal hemorrhage after threatened or elective abortions in the first trimester. A randomized, blinded clinical trial is the most convincing method to determine the true efficacy of a treatment because it reduces bias and confounding. The only randomized double-blind controlled study evaluating the
NS NS 44 <12 wk, 40 >12 wk, 12 NS All >12 wk ND NS 8-16 wk All <8 wk 8 wk 3 d <12 wk <20 wk
benefit of prophylactic Rh immune globulin for Rh(D)negative women with first-trimester pregnancy loss or abortion was performed by Visscher and Visscher7 in 1971. Rh-negative women with Rh-positive fathers undergoing a spontaneous abortion (complete or incomplete) were randomized to receive Rh immune globulin (300 U) or a placebo. A total of 57 women were followed up for 6 months. Nineteen women received Rh immune globulin and 29 received homologous gamma globulin (placebo) and 9 Rh-negative women did not receive any placebo. No patient in either group became immunosensitized. Thus, in the only well-designed trial to evaluate the benefit of Rh immune globulin in the first trimester, the incidence of isoimmunization was zero, with (0/19) or without (0/38) treatment. Critique of the data The data available to make an evidence-based recommendation regarding the utility of Rh immune globulin in the first trimester are extremely limited. Most studies were performed in the early 1970s and were not controlled. In aggregate, these data demonstrate that the number of cases of Rh-negative women who become isoimmunized after pregnancy complications or terminations in the first trimester is very low. The incidence of isoimmunization after a first-trimester abortion ranged from 0% to 3%. Gestational age was uniformly determined by dating from the last menstrual period; ultrasound was not used to confirm dating of the pregnancy. It is, therefore, possible that pregnancies thought to be in the first trimester could actually have been at >12 weeks’ gestation, which would lead to an overestimation of the incidence of immunosensitization in first-trimester abortions. Moreover, many studies evaluated the presence of a positive KB test. The KB test is at best only a surrogate marker of immunosensitization. It has yet to be definitively demonstrated that fetomaternal hemorrhage predictably results in subsequent seroconversion. Only three publications4,7,12 followed up patients for the development of antibodies (Coombs’ test) and not just the presence of fetomaternal hemorrhage (KB test). The only
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randomized, controlled trial evaluating the use of Rh immune globulin in the first trimester demonstrated an incidence of seroconversion of 0%, although this study was small.7 Moreover, the discrepancy in the number of women who received medication or placebo casts doubt as to whether this study was appropriately randomized and blinded. In fact, 9 of 38 women who were in the control group did not even receive a placebo and were followed up as a cohort independently (6 months later) of the other patients. Questions that cannot be addressed on the basis of available data include the distinction between spontaneous and elective instrumental abortion. It is theorized that instrumentation might increase the frequency of immunosensitization.15-19 This question cannot be answered given the published data. There is also no evidence to support or refute the possibility of isoimmunization after diagnosis or treatment of an ectopic pregnancy, chorionic villus sampling, cordocentesis, or amniocentesis. The only reports studying isoimmunization after such procedures examined fetomaternal hemorrhage that was not correlated with isoimmunization and the development of anti-D antibodies.15-19 Another clinical scenario where the use of Rh immune globulin would theoretically not be beneficial is the case of an early spontaneous miscarriage or ectopic pregnancy where the gestational age is greater than 8 weeks by dates (when fetal blood is made), but the embryo has stopped growing at an earlier stage, during which time the Rh(D) antigen is not present on the surface of the RBC (ie, 12 weeks by dates but anembryonic gestation with sac consistent with 6 weeks). There is no evidence to support or refute the use of Rh immune globulin in this scenario. In some situations where the father of the fetus is easily identifiable and is accompanying the patient, testing him for Rh(D) is very helpful in case he is Rh(D) negative.
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domized trial reported in the literature. (For ethical and logistic reasons, this study will most likely never be performed.) Using the scale developed by the US Preventive Services Task force, the quality of evidence to support the use of Rh immune globulin in the first trimester of pregnancy falls into the level III category. This score is the weakest evidence supporting a given practice. Despite the weak evidence to support the use of Rh immune globulin there is little risk involved. The incidence of side effects or complications caused by the use of Rh immune globulin is rare. These risks, compared with the severity of the erythroblastosis fetalis, favor the administration of Rh immune globulin to all unsensitized Rhnegative women undergoing first-trimester abortions (spontaneous or induced) or diagnosed with an ectopic pregnancy. Additionally, there are legal implications to changing what has become a standard of care without compelling evidence. Cost-effectiveness, however, demands that we use the smallest dosage available. The standard of care is to give at least 50 µg of Rh immune globulin intramuscularly to all unsensitized Rh-negative women with an ectopic pregnancy or early-trimester abortion. The 50 µg will provide prophylaxis for a fetomaternal hemorrhage of 2.5 mL,1 which is well beyond the average bleed of 0.33 mL at 8 weeks as calculated.12 KB testing does not correlate with immunosensitization,9 is not cost effective, and should not be used to determine whether Rh immune globulin should be administered. Evidence to support the use of Rh immune globulin after diagnosis and treatment of an ectopic pregnancy is practicality nonexistent. On the basis of the above data, it is possible that treatment is only necessary if the gestational age is greater than 8 weeks from the last menstrual period. Many ectopic pregnancies develop abnormally, and development may lag behind gestational age. A rule of thumb may be to treat only those where fetal cardiac actively is visible on ultrasound examination.
Clinical recommendations Although the evidence to support the use of Rh immune globulin in the first trimester is sparse, there is theoretic evidence of its necessity. Although calculations of the amount of blood necessary to result in immunosensitization are problematic, they do suggest that fetal-maternal hemorrhage in the first trimester is of sufficient volume to potentially cause immunosensitization. Moreover, there have been cases of immunosensitization reported with first-trimester abortions, although the actual incidence is unknown. Additionally, the only randomized trial that has been published is likely underpowered and cannot be considered definitive. If we conservatively estimate the rate of seroconversion to be 2%, a properly designed study with 80% power to determine the efficacy of Rh immune globulin in the first trimester would require a sample size of approximately 100 women per group. This would be at least four times the size of the only ran-
REFERENCES
1. American College of Obstetricians and Gynecologists. Prevention of Rh D isoimmunization. Washington (DC): The College; 1999. Practice bulletin No.: 4. 2. Freda VJ. Recent advances in the Rh problem. Trans N Engl Obstet Gynecol Soc 1964;18:91-104. 3. Litwak O, Taswell H, Banner E, Keith L. Fetal erythrocytes in maternal circulation after spontaneous abortion. JAMA 1970; 215:521-34. 4. Murray S, Barron SL. Transplacental haemorrhage in induced abortion. Lancet 1972;1:954-5. 5. Queenan JT, Kubaryeh SF, Shah S, Holland B. Role of induced abortion in rhesus immunization. Lancet 1971;1:815. 6. Murray S, Barron SL, McNay RA. Transplacental haemorrhage after abortion. Lancet 1970;1:631-4. 7. Visscher RD, Visscher HC. Do Rh-negative women with an early spontaneous abortion need Rh immune prophylaxis? Am J Obstet Gynecol 1972;113:158-65. 8. Leong M, Duby S, Kinch R. Fetal-maternal transfusion following early abortion. Obstet Gynecol 1979;54:424-6.
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9. Dayton VD, Anderson DS, Crosson JT, Cruikshank SH. A case of Rh isoimmunization: should threatened first-trimester abortion be an indication for Rh immune globulin prophylaxis? Am J Obstet Gynecol 1990;163:63-4. 10. Portney DL, Kuller JA, Laifer SA, Rulin MC. Should D immunoglobulin (Rh-immune globulin) be administered to Rhnegative patients with threatened abortions? Proceedings of the annual meeting of the American College of Obstetricians and Gynecologists; 1990 May 5-10; San Francisco, Calif. San Francisco: The College; 1990. p. 19-20. 11. Von Stein GA, Munsick RA, Stiver K, Ryder K. Fetomaternal hemorrhage in threatened abortion. Obstet Gynecol 1992;79:383-6. 12. Bergstrom H, Nilson LA, Nisson L, Ruttinger L. Demonstration of Rh antigens in a 38-day-old fetus. Am J Obstet Gynecol 1967;99:130-3. 13. Mollison PL, Hughes-Jones MC, Lindsay M, Wessely J. Suppression of primary Rh immunization by passively-administered antibody: experiments in volunteers. Vox Sang 1969: 16:421-39.
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14. Zipursky A, Pollock J, Neelands P, Chown B, Israels LG. The transplacental passage of fetal red blood cells and the pathogenesis of Rh immunization during pregnancy. Lancet 1963;2:489-93. 15. Brambati B, Guercilena S, Bonnachi I, Oldrini A, Lanzani A, Piceni L. Feto-maternal transfusion after chorionic villus sampling: clinical implications. Hum Reprod 1986;1:37-40. 16. Blakemore KJ, Baumgarten A, Schoenfeld-Dimaio M, Hobbins JC, Mason EA, Mahoney MJ. Rise in maternal serum α-fetoprotein concentration after chorionic villus sampling and the possibility of isoimmunization. Am J Obstet Gynecol 1986;155:988-93. 17.Blajchman MA, Maudsley RF, Uchida I, Zipursky A. Diagnostic amniocentesis and fetal-maternal bleeding [letter]. Lancet 1974;1:993-4. 18. Daffos F, Capella-Pavlovsky M, Forestier F. Fetal blood sampling during pregnancy with use of a needle guided by ultrasound: a study of 606 consecutive cases. Am J Obstet Gynecol 1985;153:655-60. 19. Pielet BW, Socol ML, MacGregor SN, Ney JA, Dooley SL. Cordocentesis: an appraisal of risks. Am J Obstet Gynecol 1988; 159:1497-500.