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Improved results in multifetal pregnancy reduction: a report of 72 cases
Vol. 61, No.1, January 1994
FERTILITY AND STERILITY Copyright
©
Printed on acid-free paper in U. S. A.
1994 The American Fertility Society
Improved results in multifetal pregnancy reduction: a report of 72 cases
Shlomo Lipitz, M.D. * Yuval Varon, M.D. Josef Shalev, M.D.
Reuven Achiron, M.D. Mati Zolti, M.D. Shlomo Mashiach, M.D.
Department of Obstetrics and Gynecology, The Chaim Sheba Medical Center, Tel Hashomer, and The Sachler School of Medicine, Tel Aviv University, Tel Aviv, Israel
Objective: To evaluate pregnancy outcome after either transabdominal or transvaginal multifetal pregnancy reduction. Design: A study of 72 consecutive multi fetal pregnancy reductions. Setting: Department of Obstetrics and Gynecology, The Chaim Sheba Medical Center Tel Hashomer, Israel. Patients: Seventy-two patients with multifetal pregnancies: 2 twins, 27 triplets, 26 quadruplets, 10 quintuplets, 3 sextuplets, 1 septuplet, 2 nontuplets, and one pregnancy with 12 fetuses. Intervention: Multifetal pregnancy reduction was performed at 9 to 13 weeks' gestation by either transabdominal or transvaginal potassium chloride injection. Main Outcome Measures: Early and late complications related to the procedure, outcome of pregnancy, and comparison of two periods. Results: Procedures performed between 1984 and 1989 (36 patients) were associated with a 33.3% pregnancy loss, whereas those performed between 1990 and 1992 (36 patients) were associated with no pregnancy loss. Of the 17 patients with quintuplets or more, 10 (59%) delivered live and healthy newborns. No difference was found when comparing the transabdominal and the transvaginal approaches. Conclusions: Both transvaginal and transabdominal approaches are comparable. There is a remarkable decrease in pregnancy loss with experience. Fertil Steril 1994;61:59-61 Key Words: Multifetal pregnancy reduction, multiple pregnancy, ovulation induction
Multifetal pregnancies are a common complication of infertility treatment because of the increased use of superovulatory agents and assisted reproductive techniques. When, despite precautions, multifetal pregnancies do occur, multifetal pregnancy reduction seems a reasonable solution in an attempt to increase the chance of delivering infants mature enough to survive without irreversible
Received February 1993; revised and accepted September 21, 1993. * Reprint requests: Shlomo Lipitz, M.D., Department of Obstetrics and Gynecology, The Chaim Sheba Medical Center, Tel Hashomer 52621, Israel. Vol. 61, No.1, January 1994
damage (1-3). Where triplets are concerned, however, it is not certain whether multi fetal pregnancy reduction necessarily improves pregnancy outcome (4). Various approaches and techniques for reduction of multifetal pregnancies have been reported: transcervical aspiration of the lower gestational sacs (5, 6), injection of potassium chloride (Kel) either transabdominally (1, 7-10) or transvaginally (11, 12), sodium chloride injection (13), and transvaginal embryo aspiration (14). Reported pregnancy loss with these methods has ranged from 5% to 40%. Our initial results concurred (12). This report describes the improved outcome, with experience, of 72 multifetal pregnancy reductions performed in a single perinatal center. Lipitz et al.
Improved results in fetal reduction
59
MATERIALS AND METHODS
During the period 1986 through 1992, 72 patients with multifetal pregnancies underwent fetal reduction at The Chaim Sheba Medical Center. All the patients were treated, followed up, and delivered at the hospital. The study included 2 twins (reduced to singletons), 27 triplets (26 reduced to twins and 1 to a singleton), 26 quadruplets (23 reduced to twins and 3 to triplets), 10 quintuplets (8 reduced to triplets and 2 to twins), 3 sextuplets (2 reduced to twins and 1 to a triplet), 1 septuplet (reduced to a triplet), 2 nontuplets (1 reduced to a twin and 1 to a triplet), and one pregnancy with 12 live fetuses reduced to a triplet. The pregnancies were conceived by IVF -ET in 17 women (23.6%), subsequent to ovulation induction with either clomiphene citrate or hMG and hCG in 54 patients (75%), and spontaneously in one woman (1.4%). The policy at our department is to recommend multifetal pregnancy reduction usually to twins when there are four or more fetuses. Patients with triplets are informed of the outcome of such pregnancies. The option of pregnancy reduction is not excluded if requested by the patients. With twins, a selective fetal termination is recommended only in cases of fetal abnormalities. The multifetal pregnancy reduction procedure was performed by ultrasound-guided intrathoracic injection of KCl as previously reported (12). The procedure was performed transabdominally in 49 patients (usually at 10 to 13 weeks' gestation) and transvaginally in 21 patients (usually at 9 to 11 weeks' gestation). In 2 other patients (a nontuplet and the pregnancy with 12 fetuses), a combined procedure was performed, namely, both the transabdominal and the transvaginal approaches were employed. All the reduction procedures were performed by two authors (S.L. and J.S.). Results were analyzed statistically by Student's t-test and Fisher's exact test. The various data are expressed as means ± SD.
nancy, IUFD of 1 fetus occurred at 26 weeks. One case of neonatal death due to hyaline membrane disease occurred in a pregnancy reduced from quadruplets to triplets. Satisfactory outcome of pregnancy, as defined by the discharge of at least one infant, occurred in 60 (83.3%) patients. Of the 17 patients with high-order multi fetal pregnancies, namely, quintuplets or more, 7 (41%) aborted before 25 weeks of gestation. Ten patients (59%) delivered live and healthy newborns, including the pregnancy that initially had 12 fetuses. The mean gestational age at the time of delivery was not significantly different between triplets and quadruplets reduced to twins (37.1 ± 2.0 versus 35.8 ± 2.5 weeks, respectively). The mean gestational age was higher by 3.5 weeks in multifetal pregnancies reduced to twins (36.5 ± 2.3 weeks) compared with the pregnancies reduced to triplets (33.0 ± 2.2 weeks, P < 0.0001). The average birth weight was also higher in pregnancies reduced to twins (2,377 ± 449 g) compared with those reduced to triplets (1,678 ± 345 g, P < 0.0001). Of the 10 women with high-order multifetal pregnancies (quintuplets or more) who delivered, 2 had done so at 26 to 32 weeks, 4 at 33 to 36 weeks, and 4 at 37 or more weeks. The results of multi fetal pregnancy reduction, comparing two time periods (before and after January 1, 1990), are shown in Table 1. A significantly higher proportion of pregnancy loss occurred among patients who underwent reduction before 1990 (12 pregnancies, 33.3%), compared with none in pregnancies reduced since 1990 (P = 0.0001). Of the 49 cases in whom the transabdominal procedure was performed, there were 8 cases of pregnancy loss (16.3%), whereas in the 21 patients who underwent a transvaginal reduction, there were 3 cases of pregnancy loss (14.3%), not statistically different from the transabdominal procedure. One pregnancy loss occurred in a patient with nontuplets in whom a combined approach was employed. DISCUSSION
RESULTS
Among the triplet pregnancies reduced to either twins or singleton, four (14.8%) resulted in spontaneous abortions before 26 weeks' gestation. In an additional patient, intrauterine fetal demise (IUFD) of 1 fetus occurred 1 day after the reduction procedure. Among the quadruplets reduced to twins or triplets, there was only one (3.8%) pregnancy loss before 26 weeks' gestation. In another preg60
Lipitz et al.
Improved results in fetal reduction
Multifetal pregnancy reduction is becoming a common practice in centers that treat infertility. As with every newly acquired procedure, there is an expected decrease in failure rate with growing experience. Indeed, a significantly lower rate of pregnancy loss (P = 0.0001) occurred in the second period (since 1990) as compared with the first period (before 1990). This may be biased by the fact that during the first period, there were more high-order Fertility and Sterility
Table 1
Results of Fetal Reduction in 72 Patients: Comparing Results Before and After 1/1/90 1986 to 1989
Initial no. of fetuses
No. of patients
Pregnancy loss :0;;25 weeks
1990 to 1992 Length of gestation*
No. of patients
Pregnancy loss :0;;25 weeks
Length of gestation*
wk
Twins and triplets Quadruplets Quintuplets and more Total
8 15 13 36
4 1 7 12
(50.0lt (6.7) (53.8) (33.3)
* Pregnancies that resulted in deliveries (>25 weeks). Values are means ± SD. t Values in parentheses are percents. :j:P = 0.003. multi fetal pregnancy reductions (quintuplets or more), whereas during the second period, a greater proportion of the pregnancies reduced were triplets. However, comparison within each category shows a significant improvement for twins and triplets (P = 0.003) and for high-order multifetal pregnancies, an improvement bordering on significance (P = 0.08). Several methods for multifetal pregnancy reductions have been proposed (1, 5-14), but none has been proven yet to be superior to others because of a lack of comparative studies. Our results show that both the transabdominal and the transvaginal routes are comparable, although we have not randomized approaches. Our series includes 17 high-order multi fetal pregnancies with the abortion rate in these patients being relatively high (41.2 %). However, perinatal outcome for those who did not abort was no worse compared with those of low-order multi fetal pregnancies that were reduced and certainly better than nonintervention (3, 15). Moreover, most reductions were performed during the first period when experience was still wanting. If the trend for improvement with time is manifested in such high-order pregnancies as is true for triplets, then still better results may be expected.
REFERENCES 1. Evans MI, Dommergues M, Wapner RJ, Lynch L, Dumez Y, Goldberg JD, et al. Efficacy of transabdominal multifetal pregnancy reduction: collaborative experience among the world's largest centers. Obstet Gynecol 1993;82:61-6. 2. Tabsh KM. A report of 131 cases of multifetal pregnancy reduction. Obstet Gynecol 1993;82:57-60.
Vol. 61, No.1, January 1994
33.2 36.0 35.5 35.5
± ± ± ±
wk
2.5t 2.7 2.8 2.9
21 11 4 36
O:j: O§
011 011
37.2 35.6 34.6 35.8
± ± ± ±
2.1 2.2 3.0 2.7
§ Not significant. liP = 0.08. 11 P = 0.0001.
3. Melgar CA, RosenfeldDL, Rawlinson K, Greenberg M. Perinatal outcome after multifetal reduction to twins compared with nonreduced multiple gestations. Obstet Gynecol 1991;78:763-6. 4. Porreco RP, Burke MS, Hendrix ML. Multifetal reduction of triplets and pregnancy outcome. Obstet Gynecol 1991;78:335-9. 5. Salat-Baroux J, Aknin J, Antoine JM, Alamowitch R. The management of multiple pregnancies after induction for superovulation. Hum Reprod 1988;3:399-401. 6. Itskovitz J, Boldes R, Thaler I, Levron J, Rottem S, Brandes JM. First trimester selective reduction in multiple pregnancy guided by transvaginal sonography. Clin Ultrasound 1990;18:323-7. 7. Berkowitz RL, Lynch L, Chitkara U, Wilkins lA, Mehalek KE, Alvarez E. Selective reduction of multifetal pregnancies in the first trimester. N Engl J Med 1988;318:1043-7. 8. Wapner RJ, Davis GH, Johnson A, Weinblatt VJ, Fischer RL, Jackson LG, et al. Selective reduction of multifetal pregnancies. Lancet 1990;335:90-3. 9. Tabsh KM. Transabdominal multifetal pregnancy reduction: report of 40 cases. Obstet Gynecol 1990;75:739-41. 10. Lynch L, Berkowitz RL, Chitkara U, Alvarez M. First-trimester transabdominal multifetal pregnancy reduction: a report of 85 cases. Obstet Gynecol 1990;75:735-8. 11. Gonen Y, Blankier J, Casper RF. Transvaginal ultrasound in selective embryo reduction for multiple pregnancy. Obstet Gynecol 1990;75:720-2. 12. Shalev J, Frenkel Y, Goldenberg M, Shalev E, Lipitz S, Barkai G, et al. Selective reduction in multiple gestations: pregnancy outcome after transvaginal and transabdominal needle-guided procedures. Fertil Steril 1989;52:416-20. 13. Yovel I, Varon Y, Amit A, Botchan A, David MP, Peyser MR, et al. Embryo reduction using saline injection: comparison between the transvaginal and the transabdominal approach. Hum Reprod 1992;7:1173-5. 14. Itskovitz-Eldor J, Drugan A, Levron J, Thaler I, Brandes JM. Transvaginal embryo aspiration-a safe method for selective reduction in multiple pregnancies. Fertil Steril 1992;58:351-5. 15. Alvarez M, Berkowitz RL. Multifetal gestation. Clin Obstet Gynecol 1990;33:79-87.
Lipitz et al.
Improved results in fetal reduction
61
FERTILITY AND STERILITY Copyright
©
Printed on acid-free paper in U. S. A.
1994 The American Fertility Society
Improved results in multifetal pregnancy reduction: a report of 72 cases
Shlomo Lipitz, M.D. * Yuval Varon, M.D. Josef Shalev, M.D.
Reuven Achiron, M.D. Mati Zolti, M.D. Shlomo Mashiach, M.D.
Department of Obstetrics and Gynecology, The Chaim Sheba Medical Center, Tel Hashomer, and The Sachler School of Medicine, Tel Aviv University, Tel Aviv, Israel
Objective: To evaluate pregnancy outcome after either transabdominal or transvaginal multifetal pregnancy reduction. Design: A study of 72 consecutive multi fetal pregnancy reductions. Setting: Department of Obstetrics and Gynecology, The Chaim Sheba Medical Center Tel Hashomer, Israel. Patients: Seventy-two patients with multifetal pregnancies: 2 twins, 27 triplets, 26 quadruplets, 10 quintuplets, 3 sextuplets, 1 septuplet, 2 nontuplets, and one pregnancy with 12 fetuses. Intervention: Multifetal pregnancy reduction was performed at 9 to 13 weeks' gestation by either transabdominal or transvaginal potassium chloride injection. Main Outcome Measures: Early and late complications related to the procedure, outcome of pregnancy, and comparison of two periods. Results: Procedures performed between 1984 and 1989 (36 patients) were associated with a 33.3% pregnancy loss, whereas those performed between 1990 and 1992 (36 patients) were associated with no pregnancy loss. Of the 17 patients with quintuplets or more, 10 (59%) delivered live and healthy newborns. No difference was found when comparing the transabdominal and the transvaginal approaches. Conclusions: Both transvaginal and transabdominal approaches are comparable. There is a remarkable decrease in pregnancy loss with experience. Fertil Steril 1994;61:59-61 Key Words: Multifetal pregnancy reduction, multiple pregnancy, ovulation induction
Multifetal pregnancies are a common complication of infertility treatment because of the increased use of superovulatory agents and assisted reproductive techniques. When, despite precautions, multifetal pregnancies do occur, multifetal pregnancy reduction seems a reasonable solution in an attempt to increase the chance of delivering infants mature enough to survive without irreversible
Received February 1993; revised and accepted September 21, 1993. * Reprint requests: Shlomo Lipitz, M.D., Department of Obstetrics and Gynecology, The Chaim Sheba Medical Center, Tel Hashomer 52621, Israel. Vol. 61, No.1, January 1994
damage (1-3). Where triplets are concerned, however, it is not certain whether multi fetal pregnancy reduction necessarily improves pregnancy outcome (4). Various approaches and techniques for reduction of multifetal pregnancies have been reported: transcervical aspiration of the lower gestational sacs (5, 6), injection of potassium chloride (Kel) either transabdominally (1, 7-10) or transvaginally (11, 12), sodium chloride injection (13), and transvaginal embryo aspiration (14). Reported pregnancy loss with these methods has ranged from 5% to 40%. Our initial results concurred (12). This report describes the improved outcome, with experience, of 72 multifetal pregnancy reductions performed in a single perinatal center. Lipitz et al.
Improved results in fetal reduction
59
MATERIALS AND METHODS
During the period 1986 through 1992, 72 patients with multifetal pregnancies underwent fetal reduction at The Chaim Sheba Medical Center. All the patients were treated, followed up, and delivered at the hospital. The study included 2 twins (reduced to singletons), 27 triplets (26 reduced to twins and 1 to a singleton), 26 quadruplets (23 reduced to twins and 3 to triplets), 10 quintuplets (8 reduced to triplets and 2 to twins), 3 sextuplets (2 reduced to twins and 1 to a triplet), 1 septuplet (reduced to a triplet), 2 nontuplets (1 reduced to a twin and 1 to a triplet), and one pregnancy with 12 live fetuses reduced to a triplet. The pregnancies were conceived by IVF -ET in 17 women (23.6%), subsequent to ovulation induction with either clomiphene citrate or hMG and hCG in 54 patients (75%), and spontaneously in one woman (1.4%). The policy at our department is to recommend multifetal pregnancy reduction usually to twins when there are four or more fetuses. Patients with triplets are informed of the outcome of such pregnancies. The option of pregnancy reduction is not excluded if requested by the patients. With twins, a selective fetal termination is recommended only in cases of fetal abnormalities. The multifetal pregnancy reduction procedure was performed by ultrasound-guided intrathoracic injection of KCl as previously reported (12). The procedure was performed transabdominally in 49 patients (usually at 10 to 13 weeks' gestation) and transvaginally in 21 patients (usually at 9 to 11 weeks' gestation). In 2 other patients (a nontuplet and the pregnancy with 12 fetuses), a combined procedure was performed, namely, both the transabdominal and the transvaginal approaches were employed. All the reduction procedures were performed by two authors (S.L. and J.S.). Results were analyzed statistically by Student's t-test and Fisher's exact test. The various data are expressed as means ± SD.
nancy, IUFD of 1 fetus occurred at 26 weeks. One case of neonatal death due to hyaline membrane disease occurred in a pregnancy reduced from quadruplets to triplets. Satisfactory outcome of pregnancy, as defined by the discharge of at least one infant, occurred in 60 (83.3%) patients. Of the 17 patients with high-order multi fetal pregnancies, namely, quintuplets or more, 7 (41%) aborted before 25 weeks of gestation. Ten patients (59%) delivered live and healthy newborns, including the pregnancy that initially had 12 fetuses. The mean gestational age at the time of delivery was not significantly different between triplets and quadruplets reduced to twins (37.1 ± 2.0 versus 35.8 ± 2.5 weeks, respectively). The mean gestational age was higher by 3.5 weeks in multifetal pregnancies reduced to twins (36.5 ± 2.3 weeks) compared with the pregnancies reduced to triplets (33.0 ± 2.2 weeks, P < 0.0001). The average birth weight was also higher in pregnancies reduced to twins (2,377 ± 449 g) compared with those reduced to triplets (1,678 ± 345 g, P < 0.0001). Of the 10 women with high-order multifetal pregnancies (quintuplets or more) who delivered, 2 had done so at 26 to 32 weeks, 4 at 33 to 36 weeks, and 4 at 37 or more weeks. The results of multi fetal pregnancy reduction, comparing two time periods (before and after January 1, 1990), are shown in Table 1. A significantly higher proportion of pregnancy loss occurred among patients who underwent reduction before 1990 (12 pregnancies, 33.3%), compared with none in pregnancies reduced since 1990 (P = 0.0001). Of the 49 cases in whom the transabdominal procedure was performed, there were 8 cases of pregnancy loss (16.3%), whereas in the 21 patients who underwent a transvaginal reduction, there were 3 cases of pregnancy loss (14.3%), not statistically different from the transabdominal procedure. One pregnancy loss occurred in a patient with nontuplets in whom a combined approach was employed. DISCUSSION
RESULTS
Among the triplet pregnancies reduced to either twins or singleton, four (14.8%) resulted in spontaneous abortions before 26 weeks' gestation. In an additional patient, intrauterine fetal demise (IUFD) of 1 fetus occurred 1 day after the reduction procedure. Among the quadruplets reduced to twins or triplets, there was only one (3.8%) pregnancy loss before 26 weeks' gestation. In another preg60
Lipitz et al.
Improved results in fetal reduction
Multifetal pregnancy reduction is becoming a common practice in centers that treat infertility. As with every newly acquired procedure, there is an expected decrease in failure rate with growing experience. Indeed, a significantly lower rate of pregnancy loss (P = 0.0001) occurred in the second period (since 1990) as compared with the first period (before 1990). This may be biased by the fact that during the first period, there were more high-order Fertility and Sterility
Table 1
Results of Fetal Reduction in 72 Patients: Comparing Results Before and After 1/1/90 1986 to 1989
Initial no. of fetuses
No. of patients
Pregnancy loss :0;;25 weeks
1990 to 1992 Length of gestation*
No. of patients
Pregnancy loss :0;;25 weeks
Length of gestation*
wk
Twins and triplets Quadruplets Quintuplets and more Total
8 15 13 36
4 1 7 12
(50.0lt (6.7) (53.8) (33.3)
* Pregnancies that resulted in deliveries (>25 weeks). Values are means ± SD. t Values in parentheses are percents. :j:P = 0.003. multi fetal pregnancy reductions (quintuplets or more), whereas during the second period, a greater proportion of the pregnancies reduced were triplets. However, comparison within each category shows a significant improvement for twins and triplets (P = 0.003) and for high-order multifetal pregnancies, an improvement bordering on significance (P = 0.08). Several methods for multifetal pregnancy reductions have been proposed (1, 5-14), but none has been proven yet to be superior to others because of a lack of comparative studies. Our results show that both the transabdominal and the transvaginal routes are comparable, although we have not randomized approaches. Our series includes 17 high-order multi fetal pregnancies with the abortion rate in these patients being relatively high (41.2 %). However, perinatal outcome for those who did not abort was no worse compared with those of low-order multi fetal pregnancies that were reduced and certainly better than nonintervention (3, 15). Moreover, most reductions were performed during the first period when experience was still wanting. If the trend for improvement with time is manifested in such high-order pregnancies as is true for triplets, then still better results may be expected.
REFERENCES 1. Evans MI, Dommergues M, Wapner RJ, Lynch L, Dumez Y, Goldberg JD, et al. Efficacy of transabdominal multifetal pregnancy reduction: collaborative experience among the world's largest centers. Obstet Gynecol 1993;82:61-6. 2. Tabsh KM. A report of 131 cases of multifetal pregnancy reduction. Obstet Gynecol 1993;82:57-60.
Vol. 61, No.1, January 1994
33.2 36.0 35.5 35.5
± ± ± ±
wk
2.5t 2.7 2.8 2.9
21 11 4 36
O:j: O§
011 011
37.2 35.6 34.6 35.8
± ± ± ±
2.1 2.2 3.0 2.7
§ Not significant. liP = 0.08. 11 P = 0.0001.
3. Melgar CA, RosenfeldDL, Rawlinson K, Greenberg M. Perinatal outcome after multifetal reduction to twins compared with nonreduced multiple gestations. Obstet Gynecol 1991;78:763-6. 4. Porreco RP, Burke MS, Hendrix ML. Multifetal reduction of triplets and pregnancy outcome. Obstet Gynecol 1991;78:335-9. 5. Salat-Baroux J, Aknin J, Antoine JM, Alamowitch R. The management of multiple pregnancies after induction for superovulation. Hum Reprod 1988;3:399-401. 6. Itskovitz J, Boldes R, Thaler I, Levron J, Rottem S, Brandes JM. First trimester selective reduction in multiple pregnancy guided by transvaginal sonography. Clin Ultrasound 1990;18:323-7. 7. Berkowitz RL, Lynch L, Chitkara U, Wilkins lA, Mehalek KE, Alvarez E. Selective reduction of multifetal pregnancies in the first trimester. N Engl J Med 1988;318:1043-7. 8. Wapner RJ, Davis GH, Johnson A, Weinblatt VJ, Fischer RL, Jackson LG, et al. Selective reduction of multifetal pregnancies. Lancet 1990;335:90-3. 9. Tabsh KM. Transabdominal multifetal pregnancy reduction: report of 40 cases. Obstet Gynecol 1990;75:739-41. 10. Lynch L, Berkowitz RL, Chitkara U, Alvarez M. First-trimester transabdominal multifetal pregnancy reduction: a report of 85 cases. Obstet Gynecol 1990;75:735-8. 11. Gonen Y, Blankier J, Casper RF. Transvaginal ultrasound in selective embryo reduction for multiple pregnancy. Obstet Gynecol 1990;75:720-2. 12. Shalev J, Frenkel Y, Goldenberg M, Shalev E, Lipitz S, Barkai G, et al. Selective reduction in multiple gestations: pregnancy outcome after transvaginal and transabdominal needle-guided procedures. Fertil Steril 1989;52:416-20. 13. Yovel I, Varon Y, Amit A, Botchan A, David MP, Peyser MR, et al. Embryo reduction using saline injection: comparison between the transvaginal and the transabdominal approach. Hum Reprod 1992;7:1173-5. 14. Itskovitz-Eldor J, Drugan A, Levron J, Thaler I, Brandes JM. Transvaginal embryo aspiration-a safe method for selective reduction in multiple pregnancies. Fertil Steril 1992;58:351-5. 15. Alvarez M, Berkowitz RL. Multifetal gestation. Clin Obstet Gynecol 1990;33:79-87.
Lipitz et al.
Improved results in fetal reduction
61