1 Department of Obstetrics and Gynecology, McGill University, Montréal, Canada
2 To whom correspondence should be addressed at: Department of Obstetrics and Gynecology, McGill University, Royal Victoria Hospital, 687, avenue des Pins Ouest, Montréal, Canada H3A 1A1. e-mail: william.buckett{at}muhc.mcgill.ca
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Abstract |
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Key words: assisted reproduciton/success rates/multiple gestation/informed choice
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Introduction |
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Multiple gestation is now a major problem associated with ART and ovulation induction therapies. The multiple gestation rates, particularly high order multiple gestation (triplets and above), can be reduced by reducing the numbers of embryos transferred, including the introduction of elective single embryo transfer (SET) (Vilska et al., 1999; Martikainen et al., 2001
; Gerris et al., 2002
; De Sutter et al., 2003
; Soderstrom-Anttila et al., 2003
). However, most authorities would concede, rather than adopting an absolute limit of the number of embryos that can be transferred, that the number of embryos transferred should be individualized for each couple (Van Steirteghem et al., 2003
). Improvements in ovarian stimulation, embryo selection, preimplantation aneuploidy screening and embryo cryopreservation techniques will also allow the number of embryos transferred to be reduced with less impact on the overall success of treatment.
However, the adoption of the singleton term gestation per cycle started as the measure of success would undoubtedly focus on, and increase the use of, elective SET. Is this in all our patients best interests? There are major national and international differences in the demographics of couples seeking treatment and also in the provision of treatment of infertility as well as the funding of health care as a whole. Although programmes which have introduced elective SET for a significant proportion of couples have not demonstrated any decline in clinical pregnancy rates (Gerris et al., 2002; Tiitinen et al., 2003
), data from Canada (Canadian Fertility and Andrology Society, 2003
) and the USA (Toner, 2002
) continue to show a year-on-year increase in clinical pregnancy rates. Therefore, what may be most appropriate for couples in one country or region may not necessarily be ideal elsewhere.
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Measurement of success |
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Despite these different and often complementary methods of measuring the success of particular medical interventions, none seeks to exclude from the successes those in whom complications have occurred; for example, a urinary or wound infection does not reduce the efficacy of a hysterectomy in the treatment of persistent refractive menorrhagia. In other words, suffering a complication of treatment does not mean that the treatment has failed!
Many couples seeking ART also make decisions concerning other treatments for infertility, for example reversal of tubal ligation versus IVF for previous tubal ligation, or intrauterine insemination versus IVF for unexplained infertility in a woman over 38 years of age. To allow appropriate comparisons, consistent measures of success for all types of infertility treatment are therefore appropriate.
The inconsistency of excluding cases where complications have occurred (namely multiple pregnancy) from overall rates of success would also deny the existence of the concept of a partial or acceptable success; for example, a woman who had suffered repeat mid-trimester pregnancy losses would accept that delivery at 34 weeks would still represent a treatment success, although the delivery would still be pre-term and have consequent but reduced risks.
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The risks of multiple pregnancy |
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Raw maternal mortality rates are 23 times higher in all multiple pregnancies (10.214.9 per 100 000) compared with all singleton pregnancies (4.45.2 per 100 000) in Europe (Senat et al., 1998). Although this is significant, it is less than the increased risk of thromboembolism whilst taking third-generation oral contraceptive pills (25 per 100 000) compared with non-users (5 per 100 000) (Drife, 2002
).
Neonatal mortality is also significantly higher in multiple pregnancy and increases with the number of fetuses. Raw neonatal mortality rates are 5 times higher for twin pregnancies (31 per 1000 live births) compared with singleton pregnancies (6 per 1000 live births) (Russell et al., 2003
). Neonatal mortality rates for triplet pregnancy, however, are
20 times higher, i.e. in the region of 100120 per 1000 live births (Doyle., 1996
). Therefore, while most couples would wish to avoid the 1012% chance of neonatal death as well as significant morbidity associated with triplet pregnancies, many may chose to accept a 3% versus 0.6% chance of neonatal death when comparing a twin versus a singleton pregnancy. These risks do not account for monochorionicity, which is associated with poorer outcomes and is more common in spontaneous twin pregnancies compared with twin pregnancies resulting from ART (Derom et al., 2001
).
Cerebral palsy is the most significant neurological impairment associated with multiple birth and is also increased by 46 times in twin delivery (912 per 1000 first year survivors) compared with singleton delivery (2.3 per 1000 first year survivors) (Petterson et al., 1993; Pharoah and Cooke, 1996
). Again, the risk in triplet deliveries is exponentially higher at 1820 times (45 per 1000 first year survivors). Similarly, some couples may accept the increased risks of twin pregnancy, but not those associated with a triplet pregnancy.
Although much more difficult to quantify, multiple births are also associated with a higher prevalence of maternal depression (Thorpe et al., 1991), parental stress and sibling problems (Bryan, 2003
).
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Conclusions |
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References |
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