In Spain, as in most Western countries, the rate of twin deliveries has doubled in the last 20 years (75 out of 10,000 deliveries in 1980 and 175 out of 10,000 deliveries in 2004), and the rate of triplet deliveries has shown a sixfold increase (11 out of 10,000 deliveries in 1980 and 60 out of 10,000 deliveries in 2004) Citation[1]. Our prematurity rates are at approximately 8% of deliveries, and despite improved sociohealth conditions and scientific progress, they have not varied much over the last 10 years. Severe complications due to extreme prematurity, such as cerebral palsy, increase exponentially with multiplicity of pregnancy Citation[1].
Pregnancy rates achieved in oocyte donation programs are higher than those obtained in patients treated with IVF with their own oocytes. According to the data published in the 2006 Registry of the Spanish Fertility Society, the clinical pregnancy rate with standard IVF/intracytoplasmic sperm injection was 38%, whereas it was 50% with IVF after oocyte donation. However, with oocyte donation, more than one embryo is usually transferred, and the multiple pregnancy rate is excessively high, ranging between 20 and 45%. The responsibility for preventing multiple pregnancies lies with healthcare professionals, who must be aware of the risks involved in these pregnancies, and should promote among patients and physicians policies for the selective reduction of the number of embryos to be transferred.
In this very competitive world, most oocyte donation programs consider a high clinical pregnancy rate to be the most important outcome to be presented to the patients, and they do not highlight the cumulative pregnancy rates obtained with fresh plus frozen cycles Citation[2–4]. The emotional and financial difficulties that patients suffer while repeating several attempts could be the reason why centers try to obtain the maximum result in the first cycle. With oocyte donation, there is limited information comparing single-embryo transfer (SET) and double-embryo transfer (DET) Citation[5], although some scientific societies have established different guidelines on the number of embryos to be replaced in women receiving donated oocytes.
In our experience looking at cumulative pregnancy rates achieved with oocyte donation with fresh SET and DET plus subsequent frozen cycles Citation[6], we have observed that pregnancy rates were lower with SET (28 out of 58; 43.1%) than with DET (463 out of 816; 56.7%; p < 0.05). However, the multiple pregnancy rate was 38.4% with DET (178 out of 463), while no multiples were obtained after SET (p < 0.05), and no differences were observed for live birth rates with 34.5% after SET and 44% after DET. For frozen cycles, SET and DET policies were not applied, and after replacing a similar number of embryos the twin rate and cumulative live birth rates were 16.7 and 75.9% with SET and 20% and 63.4% with DET, respectively (nonsignificant). With oocyte donation, the only predictive factor for multiple pregnancy is embryo quality and, for this reason, the authors believe it should be recommended to transfer one single embryo when several good-quality embryos are available Citation[7]. Reducing multiple pregnancies is especially relevant in oocyte donation cycles, given that most of the recipients are of advanced age and already have a higher risk of obstetrical and neonatal complications.
We are now aware of the fact that some women decide later in life that they want to have a child, and that this may explain the increase in the use of oocyte donation. It is crucial to inform patients and physicians about the maternal and neonatal risks involved, and encourage professionals to selectively replace a single embryo in oocyte donation cycles, with the oocytes coming from young donors with good-quality embryos Citation[8]. Scientific societies, as well as professionals, must raise awareness of these risks, and provide fertile couples with objective information, obtained from ongoing prospective studies on cumulative pregnancy rates, before they start an oocyte reception cycle.
Financial & competing interests disclosure
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.
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