ASRM称卵子冷冻技术已越过试验阶段

美国生殖医学会(ASRM)已认可，将卵母细胞冷冻保存技术作为因医学治疗而可能危及生育能力的年轻女性的一种选择。

该学会发布的一份报告认为，卵子冷冻技术的进步使得采用该项技术体外受精(IVF)女性的妊娠率和健康婴儿出生率堪比采用新鲜卵子者。该学会甚至还在这份报告中不再使用“试验”一词，以此希望保险公司能够为即将接受生殖毒性治疗(如癌症化疗)的年轻女性支付卵子冷冻保存费用。

该报告的主要作者、ASRM执委会主席Samantha Pfeifer博士称，卵子冷冻保存技术可用于具有丧失生育能力医学指征的患者，诸如癌症、先兆卵巢衰竭以及特纳综合征等遗传疾病。其他指征还包括IVF当天未能收集到足够的精子，以及不能或不愿意进行胚胎冷冻的夫妇。但该报告不支持将卵母细胞冷冻保存技术用于推迟生育，或者年轻女性以此作为预防未来可能出现生育问题的“保险策略”。

Pfeifer博士指出：“我们注意到该技术在用于预防未来不育问题方面得到了大力推广。这一观念看似不错，但没有数据表明这能够帮助许多女性。仅有15%的夫妇将会尝试治疗不育问题，其中只有部分夫妇选择IVF，而需要考虑卵子冷冻保存技术的夫妇更少。只有那些在年轻时已冷冻了卵子，且后来患有不孕症的足够幸运的女性才能从中受益。”

该报告分析了有关卵母细胞冷冻保存技术安全性和有效性研究的122篇报告数据。在一项对600例受试者应用新鲜和冷冻卵母细胞进行比较的最大规模和最令人信服的随机对照试验中，研究者发现玻璃化冷冻卵母细胞解冻后存活率为92.5%，受精率(74% vs. 73%)、着床率(40% vs. 41%)以及移植后妊娠率(55.4% vs. 55.6%)与新鲜卵母细胞相比均未见显著差异。

Pfeifer博士称，研究结果还减少了人们对“冷冻可能损伤减数分裂过程中的纺锤体形成，从而导致卵子质量下降”的担忧。冷冻技术的进步在很大程度上减轻了上述担心。该报告指出，来自冷冻保存卵母细胞人体胚胎的染色体异常发生率与对照胚胎未见差异。一项对900多例冷冻卵子出生婴儿资料的最新分析报告表明，其先天异常风险并不高于对照人群。但报告也指出，至今尚缺乏这些儿童的长期发育数据。

该报告的共同作者Eric Widra博士称，同其他任何辅助生殖技术一样，20多岁和30岁出头的女性利用冷冻卵母细胞进行IVF的成功率最高。这一事实直接涉及到冷冻卵子的选择性问题。他说道：“在冷冻卵子的愿望与需要之间存在固有的矛盾。20多岁女性患有不孕症的可能性不大，如果真的患有不育症，也不大可能是卵子问题。因此，许多人以冷冻保存卵子作为保险策略将永远没有必要。而对于年龄较大的患者，冷冻卵子提供的是一种虚假的安全感，技术层面上具有可能性，但胎儿活产几率不大。”Widra博士认为，在确认卵母细胞冷冻保存最佳人选和最佳时机方面，我们还处于初级阶段。

Pfeifer博士对此表示赞同。他表示应慎重使用该项技术，在没有讨论各种可能性的情况下不能不加选择地用于所有女性。许多女性在40岁左右时对该技术颇感兴趣，但她们的胎儿活产率不如年轻女性。应提醒这些年龄较大的女性，不能认为卵子冷冻保存后，未来就有更多的选择，最佳受孕方式仍是自然受孕。没有数据支持这一技术可作为推迟生育的社会机制。

Pfeifer博士和Widra博士均报告无相关利益冲突。

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By: MICHELE G. SULLIVAN, Oncology Practice

Oocyte cryopreservation is now an officially sanctioned option for young women whose medical treatments may endanger their fertility.

A report by the American Society for Reproductive Medicine found that advances in egg-freezing techniques now produce rates of pregnancy and healthy babies comparable to those seen with vitro fertilization (IVF) using fresh eggs.

The society went so far as to remove the word "experimental" from the paper, in the hopes that insurance may begin to pay for egg preservation for young women who face gonadotoxic treatments, such as chemotherapy for cancer.

"Egg freezing can be used for patients with medical indications for losing their fertility, such as cancer, impending ovarian failure, or even genetic conditions like Turner syndrome," Dr. Samantha Pfeifer, the paper’s lead author, said during a press briefing. Other indications include a failure to retrieve sufficient sperm on the day of IVF, or the cryopreservation of eggs for couples who can’t, or don’t want to, freeze embryos.

What the paper doesn’t support, however, is using oocyte cryopreservation to delay childbearing, or as any kind of an "insurance policy" for younger women against what might happen to their fertility some time in the future.

"We are aware that this has been marketed vigorously to ensure against future infertility," said Dr. Pfeifer, chair of the ASRM Practice Committee. "Conceptually this seems like a good idea, but there are no data to say that it would help many women. Only 15% of couples will ever seek treatment for infertility, and only a subset of those will attempt IVF, and only a subset of those would need to consider cryopreservation. Only women who were lucky enough to freeze eggs [during their youth], and then become infertile, would be helped by this."

The report examined data from 112 papers on oocyte cryopreservation safety and efficacy. "The largest and most compelling randomized controlled trial compared the use of fresh versus vitrified donor oocytes in 600 recipients," the report noted. "The investigators found that 92.5% of vitrified oocytes survived warming, and that there were no significant differences in fertilization rates (74% vitrified vs. 73% fresh), implantation rates (40% vs. 41%), and pregnancy rates per transfer (55.4% vs. 55.6%) between groups."

The studies’ findings also eased concerns that freezing might compromise egg quality by damaging the meiotic spindle, Dr. Pfeifer said. Advances in the technology of freezing have largely ameliorated that fear.

"Despite concerns regarding spindle abnormalities in cryopreserved oocytes, the incidence of chromosomal abnormalities in human embryos obtained from cryopreserved oocytes is no different from that of control embryos," according to the report. A recent review of more than 900 babies born from frozen eggs found no increased risk of congenital abnormalities, compared with the background population.

However, the paper noted, there are not yet any long-term developmental data on these children.

IVF with frozen oocytes is most successful with women in their 20s and early 30s – as in any other assisted reproduction technique, said coauthor Dr. Eric Widra. This truth touches directly on the issue of elective egg freezing.

"There’s an inherent conflict between the desire to freeze eggs and the need to do it," he said during the briefing. "Young women in their 20s are unlikely to have infertility, and if they do, it’s unlikely to be due to trouble with their eggs, so freezing is an insurance policy many will never need. For the older patient, freezing provides a false sense of security; technically it would be possible, but it may not give them a good chance of a live birth.

"We are still in the early phases of figuring out the best candidate and the best time of life to elect doing this," he said.

Dr. Pfeifer agreed. "We think this application should be used with caution and not be offered indiscriminately to everyone, without counseling about the options. A lot of the women interested in this are in their late 30s and early 40s, and their chance of having a live birth is not as good as younger women. These older patients must be counseled on this. This is not a technology that says, ‘Freeze your eggs so you will have more options down the road.’ The best way to conceive is with your own eggs, through natural intercourse. There are no data that support this as a social mechanism to delay childbearing."

Dr. Pfeifer and Dr. Widra said they had no relevant financial disclosures.