1 Department of Obstetrics and Gynecology, Rambam Medical Center, POB 9602, Haifa 31096 and 2 Faculty of Medicine, Technion, Israel Institute of Technology, Israel
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Abstract |
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Key words: embryo aspiration/multiple pregnancy/selective fetal reduction/ultrasound-guided procedures
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Introduction |
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A recent collaborative report (Evans et al., 1996) estimated that following multifetal pregnancy reduction the overall pregnancy loss rate (before 24 gestational weeks) is 11.7%, and the early premature delivery rate (between 2528 gestational weeks) is 4.5%. This study also documented a direct relationship between the starting or the final number of embryos and the rate of complicationsthe higher the initial number of gestational sacs, the worse the prognosis. The reported pregnancy loss rate was 7.6% when the initial number of embryos was three and increased to 15.3% with quadruplets and higher order multiple gestations.
Previously (Itskovitz et al., 1989; Itskovitz-Eldor et al., 1992
), we suggested that early selective fetal reduction be performed by transvaginal embryo aspiration. Our preliminary results (5.3% pregnancy loss rate) showed that this procedure is at least as safe as the transabdominal or transcervical route (Itskovitz-Eldor et al., 1992
). Other advantages of transvaginal embryo aspiration include the possibility of performing it 24 weeks earlier than other methods for selective fetal reduction, thus making the procedure potentially more acceptable from religious and ethical points of view, and obviating the need to use KCl or other toxic substances.
The aim of this communication, based on experience accumulated over 10 years, is to re-evaluate the outcome of pregnancies after early transvaginal embryo aspiration for selective fetal reduction.
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Materials and methods |
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Results |
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Five pregnancies were reduced to triplets, four of them because of patient request. Among those four, three delivered triplets at 31, 34 and 35 gestational weeks. All neonates were well and healthy. The fourth delivered twins on her 36th week of gestation, following an additional late reduction of the third fetus, indicated for hydrops fetalis. In the fifth case (a quadruplet) reduction to triplets was accomplished because the location of three of the sacs did not allow reduction to twins without significant danger of losing the whole pregnancy. Intrauterine death of a second fetus occurred at 24 weeks gestation. Twins were born by Caesarean section at 29 weeks gestation.
In seven pregnancies with quadruplets or higher number of fetuses, selective fetal reduction was completed in two sessions, because of technical difficulties or clinical impression that spontaneous fetal demise would follow. The outcome of these cases is detailed in Table II. In the first session, the number of fetuses was reduced to triplets, followed by reduction to twins some days or weeks after the first procedure. All patients delivered twins at 3438 weeks gestation.
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Discussion |
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Our results indicate that early transvaginal embryo aspiration is a safe procedure, with a 6.7% total loss rate before 24 gestational weeks. This compares favourably with the 11.7% in the collaborative study (Evans et al., 1996). Comparing these results with those reported in by Evans et al. (1996), we could not document a statistically significant difference between the two studies in the complication rate for triplets that were reduced to twins. However, our procedure appeared to be significantly (P < 0.05) safer when the initial number of fetuses was four or greater (one loss out of 39 procedures versus 141 losses out of 919 procedures in the collaborative study). In our series there was no difference between the timing of reduction among triplets (mean 7.5 gestational weeks) and quadruplets or higher order pregnancies (7.5 weeks on average). Therefore, this would not explain the better results we obtained with those pregnancies. Moreover, performing selective termination in two sessions did not increase the risk of pregnancy loss. Compared to later performed procedures, transvaginal embryo aspiration is easier to accomplish. It is also possible that avoiding the burden of aborted fetuses that is left after the `late' procedures is beneficial and confers the observed advantage of our procedure. Early selective fetal reduction is more acceptable to some of our patients, both from moral and from religious points of view. In Judaism, a medically indicated abortion might be performed up to 40 days from conception (7 + 5/7 weeks menstrual age, Grazi and Wolowelsky, 1991
). In addition, our method obviates the use of KCl or other toxic substances, and the potential fetal complications that might be associated with their use. The use of intracardiac KCl in multifetal pregnancy reduction was reported as a possible risk factor for periventricular leukomalacia in premature newborns (Geva et al., 1998
).
A potential disadvantage of transvaginal aspiration at 78 weeks gestation would be selective fetal reduction performed too early, i.e. before the `natural' phenomenon of `vanishing twins' could occur (Landy et al., 1982; Dickey et al., 1990
; Landy and Keith, 1998
). The whole pregnancy may be endangered if additional embryos were to be lost spontaneously after selective reduction to the desired number of fetuses had been completed. In our study the total number of retained living embryos following selective reduction was 183. The total number of lost fetuses (both because of early pregnancy loss and premature delivery) amounted to 18. This represents 9.8% of the total and sharply contrasts with the 3060% rate of `vanishing twins' reported by others (Landy et al., 1982
; Dickey et al., 1990
). Moreover, if whole pregnancy losses are excluded, spontaneous fetal demise after heart activity had been documented on ultrasound was very low (one out of 183 embryos in this series), confirming our previous observation (Kol et al., 1993
). Kol et al. (1993) also showed that the fetus with the smaller CRL has a greater chance of spontaneous demise. In the present series, if an embryo smaller than the rest was identified, it was chosen for aspiration.
A considerable disadvantage of early transvaginal aspiration is the inability to identify the fetus with a structural anomaly that might be detected on ultrasound when the reduction is performed early in the second trimester. In triplet gestations, an alternative option (after appropriate counselling) is to defer selective reduction to the early second trimester, when ultrasound screening for fetal structural anomalies should be attempted. The rate of non-chromosomal structural malformations is indeed increased in multifetal pregnancies, but mainly in monozygotic gestations. Most multiple gestations occurring as a result of ovulation induction are derived from different zygotes. Ultrasonographic detection of congenital anomalies in multiple gestations may be hampered by fetal positioning and crowding, oligohydramnios and increased distance between the ultrasound transducer and the target organ. In twins, ultrasound screening for fetal anomalies is apparently as effective as in singleton gestations (Allen et al., 1991), but data are not available regarding the efficacy of ultrasound diagnosis of fetal structural anomalies in multiple gestations of higher order.
In summary, early transvaginal embryo aspiration is a simple and relatively safe procedure. In quadruplets or higher order gestations, this procedure is apparently safer than other methods of selective fetal reduction. Moreover, it might be more acceptable to patients from emotional and religious points of view. We suggest that early transvaginal embryo aspiration should be offered to all patients with four or more fetuses. In these cases, early reduction to twins should be attempted. Either an abnormal ultrasound or the relative position (most accessible and highest in the uterus) should target the fetus for selective reduction. Most important, further studies are needed for development of safer methods of selective fetal reduction and, more pressing, for the initial avoidance of iatrogenic high order multiple pregnancies per se.
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Notes |
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References |
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Submitted on October 29, 1998; accepted on March 24, 1999.