生育大事件：准妈妈滴血可查胎儿基因

    投资银行Poliwogg的医疗战略分析师雷斯•范特雷德认为：“至于这种产前基因检测技术是否会成为一种标准，它肯定是可能的，但是首先他们要把价格降到比现在更低的水平。那些托管型医疗保健公司不会一窝蜂地冲到新领域上去花钱。如果开发这种技术的公司能够证明它确实能提高医疗服务质量或降低成本，那么它可能会成为标准医疗保健的一部分。但是如果它反而增加了怀孕的成本，它肯定不会受到人们的热烈欢迎。”

    NIPT公司们也正在努力攻克这个问题。过去一两年里，这项技术已经取得了巨大的进步。2011年以来，好几家公司都推出了商业化的测试手段（有些从亲子鉴定开始，特别是早在怀孕8周的时候，就可以鉴定出胎儿是不是准爸爸的亲生儿子）。之后这些公司又在测试中加入了许多新的诊断目标，现在它已经可以检测包括唐氏综合症等基因病、各种不易被发现的综合症，以及各种性染色体异常。其中有些基因病在少儿时代很难检测出来，往往等到确诊之后再对孩子进行激素治疗已经为时太晚。未来这种NIPT技术还可以用来检测囊细胞纤维症、萨氏病、镰状细胞性贫血，甚至能检测出与常见癌症有关的基因。由于这种测试只是简单地从母亲的血样中提取胎儿的基因信息，因此NIPT能检测出的基因病和遗传指标的数量，最终将只是局限于医生对某一类基因的理解。

    作为一项诊断工具，目前大部分接受这项测试的人都是所谓的高风险群体——一般来说指的是35岁以上的孕妇（因为高龄产妇的胎儿更易患唐氏综合症），或者是其他存在已知染色体病变风险的人群。不过，Natera和Verinata等公司目前都在设计用于一般人群的NIPT试验，以证明这种技术同样适用于非高风险孕妇的胎儿的基因筛查。由于非高风险孕妇的比例远远高于高风险人群，因此一旦这种试验获得了成功，它可能会成为所有怀孕的准妈妈们都会选择的标准测试，变成像超声波检查一样常规的检查。

    Natera公司的CEO马特•拉比诺维茨博士表示，如果情况真的朝着这个方向方展，背后的推动因素也并不是唐氏综合症或性染色体异常等问题，而是NIPT的下一个战场——缺失症候群。缺失症候群是指一个染色体的部分或全部由于各种原因从基因中缺失了，进而导致婴儿发育期的各种生理问题。人们未必非常了解这些症候群，但是医生们知道它们的确存在，而且从事NIPT的公司也非常自信地认为，他们能够检测到这些症候群。具有这种功能的商业化检测产品在未来6到18个月里就会面世。

    拉比诺维茨说：“我非常肯定，它将会成为涵盖整个人口的一个前沿性测试。而使它覆盖整个人口的推动力就是缺失症候群。我们非常想检测出这些症候群，如果能把这种筛查测试扩大到整个人口的范围，这将是一件非常了不起的事。”

    拉比诺维茨还说，如果NIPT在整个人口范围内得到采用，它将对医疗事业产生巨大的影响。并不是只有他一个人这么想。NIPT测试本身只提取了胎儿的基因信息，因此唯一能限制其检测功用的就是医生对这些基因的临床理解。医生可以利用检测结果制定治疗方法，做出临床决策。而且根据摩尔定律，这门筛查技术的潜在用途还在以惊人的速度增长。

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    "Whether or not prenatal genetic testing becomes standard, it's certainly possible, but they're going to have to get the price point down lower than it is right now," says Les Funtleyder, a health care strategist at investment firm Poliwogg. "Managed care companies aren't rushing toward new places to spend money. If the companies in question can make the case that by doing this you're somehow improving quality or cutting costs, they could become part of standard care. But if they're adding cost onto the price of pregnancy, it won't be received enthusiastically."

    That's the case the companies in this space are working to make right now. Over the past couple of years the technology has matured tremendously, with several firms bringing commercial tests to market since 2011 (a few started as paternity tests, significant in that they could determine paternity as early as eight weeks into a pregnancy). Since then, those companies have moved quickly to pile new diagnostic targets into those tests, which now screen for everything from chromosomal disorders like Down and a number of other less-notable syndromes to various sex chromosome abnormalities, many of which go undetected in young children until they are too old for hormone treatments to be effective. In the future these same NIPT diagnostics could screen for cystic fibrosis, Tay-Sachs, sickle cell anemia, and even the presence of certain genes associated with common cancers. Because the tests themselves simply extract the genetic information from the mother's blood sample, the number of disorders and genetic indicators NIPT could eventually test for is really only limited by doctors' understanding of the genome.

    Yet as a diagnostic tool, these tests have largely been relegated to what are considered high-risk populations -- typically pregnant women 35 or older (for Down syndrome) or that carry some other known risk for a chromosomal disorder. But both Natera and Verinata are designing and conducting general population trials to prove their efficacy in spotting chromosomal and genetic issues in the unborn children of non-high-risk mothers -- a proposition that, if proven, could accelerate the adoption of NIPT across the board as a standard test for all pregnant mothers, something as routine as ultrasound.

    The impetus for this won't be Down Syndrome or sex chromosome abnormalities, says Natera CEO Dr. Matt Rabinowitz, but NIPT's next frontier, so-called deletion syndromes. These occur when all or part of a chromosome, for whatever reason, is deleted from the genome, causing various developmental problems for the child. These syndromes aren't necessarily very well understood, but doctors know they exist and the companies in the NIPT space are confident their tests can spot them -- and will do so in their commercial version within the next six to 18 months.

    "I have no doubt that this will become a front-line test across the entire population," Rabinowitz says. "And what's going to drive this to the entire population is deletion syndromes. You really want to be able to screen for these, and to be able to include these in a population-wide screen is an extremely big deal."

    That population-wide adoption will have huge public health impacts, Rabinowitz says, and he's not the only one who thinks so. The NIPT tests themselves only extract the baby's genetic information, so the only thing limiting what they can screen for is doctors' clinical understanding of the genome -- the application of that information in creating therapeutics and making clinical decisions. And with genetic science following its own kind of Moore's Law, those potential applications are growing at a prodigious rate.