少数族裔体外受精结局不佳令人困惑

    加州圣巴巴拉——加州大学洛杉矶分校（UCSF） 的Marcelle I. Cedars博士在该校主办的体外受精与胚胎移植会议上报告称，虽然有一些线索，但仍对接受体外受精（IVF）的少数族裔患者妊娠率和活胎出生率低于白人而感到十分困惑，尤其是在她们的自然妊娠率并无差异的情况下。
    人们推测上述差异可能与多种潜在因素有关，包括肥胖率、平滑肌瘤发病率、炎性过程以及雌激素代谢差异等，但没有一种因素可以完全解释亚裔美国人、黑人和西班牙裔患者IVF结局不佳。此外，黑人和西班牙裔患者与辅助生殖技术有关的流产率也相对较高。有人还认为经济差异和获得IVF机会不同也可能与之有关，但军队研究证实，即使拥有相同医疗机会，少数族裔患者的IVF结局仍不及白人，虽未达到统计学差异水平。

 
UCSF体外受精项目主任、生殖内分泌与不育研究室主任Cedars博士说：“如果我们观察所有年龄组的活胎出生率，可以看到亚裔患者活胎出生率明显较低。”

    Cedars博士课题组一直关注亚裔美国人的IVF结局，亚裔美国人约占其患者人群的1/3。经过6年多的密切观察，她们发现了上述差异。亚裔患者临床妊娠率也低于白人患者，但卵子、胚胎和高质量胚胎数目均相似，表明她们的卵巢储备功能并不存在本质区别。进一步研究显示，亚裔患者在排卵刺激期间雌二醇水平较高，即便是在严格控制刺激方案、使用相同剂量的情况下。与IVF患者一样，亚裔卵母细胞捐赠者的血清雌二醇达峰率比白人患者高出23%，但移植率、临床妊娠率和活胎出生率均未见统计学差异。
    推测环境或生活方式因素，如食用鱼类导致的较高汞暴露率可能导致不良IVF结局，但这一因素应该对自然受孕和妊娠也有影响，然而研究者未见亚裔人群自然妊娠以及妊娠时间方面存在差异。
    Cedars博士认为，或许应该更多关注患者排卵刺激药物代谢方式的差异，制定适合少数族裔患者的刺激方案。她最后指出，这是一个非常活跃的研究领域，有许多课题亟待探索。
    Cedars博士报告无相关利益冲突。
    By: BETSY BATES, Ob.Gyn. News Digital Network
    SANTA BARBARA, CALIF.  – Although there are hints, researchers remain largely baffled about why ethnic minority patients have lower pregnancy and live birth rates than do whites when they undergo in vitro fertilization, especially as natural conception rates do not appear to be disparate.
    Many potential explanations have been hypothesized, including differences in obesity rates, leiomyomata prevalence, inflammatory processes, and estrogen metabolism, Dr. Marcelle I. Cedars said at a meeting on in vitro fertilization and embryo transfer, which was sponsored by the University of California, Los Angeles.
    None seem to fully account for diminished IVF outcomes in Asian Americans, blacks, and Hispanics. Pregnancy loss rates associated with assisted reproductive techniques also are higher for blacks and Hispanics, she noted.
    Economic disparities and unequal access to IVF have been suggested as playing a role, but military studies, in which all patients have equal access to care, confirm reduced outcomes numerically – although the numbers did not quite reach statistical significance.
    Dr. Cedars’ group at the University of California, San Francisco （UCSF）， has focused on IVF outcomes in Asian Americans, who represent approximately a third of their patient population. Differences came under scrutiny beginning about 6 years ago.
    "If we looked at live birth rate overall in any age group, we saw a significantly decreased rate in the Asian population," said Dr. Cedars, director of the in vitro fertilization program and director of the division of reproductive endocrinology and infertility at UCSF.
    The clinical pregnancy rate among Asian patients also was lower than among white patients in their clinic, but the number of eggs, number of embryos, and number of high-quality embryos were similar.
    "We don’t think there is something intrinsically different in terms of their ovarian reserve," she said.
    Further investigation revealed higher estradiol levels during stimulation in Asian patients, even among those on a strictly controlled regimen, when "everyone gets the same dose," she noted.
    Asian oocyte donors, like IVF patients, had peak serum estradiol rates 23% higher than those of white donors, but their implantation, clinical pregnancy, and live birth rates were not statistically different.
    Environmental or lifestyle factors, such as higher rates of mercury exposure through fish consumption, have been hypothesized as contributing to poorer IVF outcomes, said Dr. Cedars, who also is a professor of obstetrics, gynecology, and reproductive sciences at UCSF.
    But such a factor would influence spontaneous conception and pregnancy as well as IVF.
    "When we looked at spontaneous pregnancies and time to pregnancy, there were absolutely no decrements in the Asian population," she said.
    Indeed, Dr. Cedars believes more attention should be focused on possible differences in the way patients metabolize drugs used during ovarian stimulation. "I think we really need to think about our stimulation protocols, which were not developed with [proportional representation] of these minorities."
    In the meantime, "much still remains to be explained, and this is an active area for investigation," she concluded.
    Dr. Cedars reported no financial relationships relevant to her talk.