????美國每年都會迎來大約400萬名新生嬰兒的誕生，他們的母親在產(chǎn)前都會接受同一套產(chǎn)檢流程：驗血、驗?zāi)?，分析血壓、體重、血糖，甚至是基因組，以測定胎兒是否有患上遺傳疾病的風(fēng)險。一般來說，醫(yī)生總是通過母親來測定體內(nèi)胎兒的健康狀況，只有超聲波造影是個例外。而這種技術(shù)并不完全精確。

????但是如果現(xiàn)在有了新的方法讓準(zhǔn)爸爸、準(zhǔn)媽媽們在產(chǎn)前了解更多關(guān)于胎兒的健康狀況，他們是否會樂意呢？如果只需要準(zhǔn)媽媽的一滴血，就可以知道關(guān)于胎兒的大量信息，甚至包括胎兒的整個基因組及其隱含的所有信息，準(zhǔn)爸爸、準(zhǔn)媽媽們會愿意接受這種檢查嗎？答案顯而易見。有幾家專門從事醫(yī)療診斷的公司也是這樣想的。過去一兩年里，他們推出的新一代非侵入式產(chǎn)前檢查技術(shù)（NIPT）已經(jīng)全然改變了醫(yī)生們做孕檢的方式。光是在美國，這項技術(shù)每年就為400萬準(zhǔn)媽媽們帶來了福音。

????非侵入式產(chǎn)前檢查技術(shù)來自最近的一項科研成果：一個懷孕的準(zhǔn)媽媽的血液內(nèi)存在大量胎兒的DNA片段，它們在胎盤細(xì)胞死亡和脫落之后游離進(jìn)入母親的血液中。這些DNA片段又叫游離DNA，之所以這樣命名，是因為這些DNA并非存在于一個完整的胎兒細(xì)胞的原子核中，而是在母體的血液中游蕩。它們可以從母親自己的DNA中鑒定和分離出來。事實證明，在一個準(zhǔn)媽媽的循環(huán)系統(tǒng)的所有游離DNA中，胎兒的游離DNA所占的比例可能高達(dá)20%。當(dāng)然，目前也有其它可以獲得胎兒DNA數(shù)據(jù)的技術(shù)，比如羊水穿刺，或是胎兒絨毛采樣等，但是這些技術(shù)必須通過物理手段侵入到胎兒附近（通常是通過針或管子），而這會加大流產(chǎn)和并發(fā)感染的風(fēng)險。而NIPT技術(shù)的優(yōu)點就在于，只需要準(zhǔn)媽媽的一滴血樣，就可以獲得胎兒的基因以及其中包含的所有染色體信息。

????雖然游離DNA早在15年前就被發(fā)現(xiàn)了，但是這門基因技術(shù)卻沒有很快獲得實際應(yīng)用。隨著基因技術(shù)的快速發(fā)展，這種情況一直到過去10年里才有所改變?，F(xiàn)在，非侵入性測試已經(jīng)可以拼湊出胎兒的完整基因組，并通過這些基因數(shù)據(jù)測定嬰兒是否有患上遺傳病或畸型的風(fēng)險——比如性染色體異常、唐氏綜合癥以及許多其它發(fā)育問題。早期實驗顯示，這種測試非常可靠，因此好幾家公司都在爭做NIPT領(lǐng)域的第一代領(lǐng)頭羊，其中包括Verinata【由億明達(dá)公司（Illumina）所有】、西格諾（Sequenom）、Natera、Ariosa Diagnostics和Ravgen等公司。他們相信，自己的測試技術(shù)將在未來兩三年里成為一種標(biāo)準(zhǔn)的、常規(guī)的產(chǎn)前檢查技術(shù)。

????國際戰(zhàn)略投資集團(tuán)（International Strategy and Investing Group）的醫(yī)療分析師兼常務(wù)副董事維杰?庫瑪爾說：“NIPT只需要取一滴血樣。一旦用NIPT這種簡單的技術(shù)取代了羊水穿刺等技術(shù)，人們無疑就會選擇它。但是接下來就是成本的問題了?？紤]到目前的醫(yī)療環(huán)境，這種討論會變得更艱難?！?/p>

????事實也的確如此，目前NIPT技術(shù)的最大阻礙不是技術(shù)本身而是其成本。這種測試的價格相對比較昂貴，即使是低端測試也需要800美元，更貴的高端檢查方法需要將近3,000美元。Sequenom、Natera和Ariosa Diagnostics這三家公司正因為專利打訴訟戰(zhàn)，讓人搞不清楚哪些技術(shù)到底是哪家公司的（更不用說各方的開支都有所增加）。而且這種技術(shù)對保險公司來說也太新了，雖然他們已經(jīng)認(rèn)識到了NIPT技術(shù)在預(yù)防方面的好處，但是他們還沒決定是否要給這種測試提供報銷，采用什么方式報銷。

????Every year, the U.S. welcomes 4 million new babies into the world, the result of roughly 4 million pregnancies that in large part go through the same battery of prenatal health checks 4 million times: analyses of the mother's blood and urine, of the mother's blood pressure, of the mother's weight, of the mother's blood sugar -- even of the mother's genetic makeup if she's deemed a risk for certain inheritable disorders. Ultrasound imaging being the obvious exception, doctors generally measure an unborn baby's health via the mother -- a kind of science by proxy that offers only a rough approximation of the baby's developmental health.

????But if parents could know more about their child's health before birth, wouldn't they want to? And if a bounty of health information -- even the unborn child's entire genome and all the data contained therein -- could be accessed via nothing more than a simple blood draw from the mother, wouldn't parents want to have that option? A handful of medical diagnostics companies think so, and a new generation of non-invasive prenatal tests (NIPT) they have brought to market over the past couple of years have positioned them to completely transform the way clinicians perform routine prenatal care -- a full 4 million times annually in the U.S. alone.

????NIPT technology rests on the fairly recent discovery that a pregnant mother's blood is practically swimming with fragments of her baby's DNA, deposited there as cells from the placenta die and break down. This cell-free DNA -- so named because it is not contained within the nucleus of a complete fetal cell, but rather floats free in the mother's bloodstream -- can be identified and isolated from the mother's own DNA (it turns out cell-free fetal DNA can make up as much as 20% of the free-floating DNA in a pregnant mother's circulatory system). There are other ways to access fetal DNA of course -- Amniocentesis for instance, or the more accurate chorionic villus sampling (or CVS) test -- but these require a physical incursion into the neighborhood of the fetus itself (usually via a long needle or tube) which ups the risk of miscarriage and pregnancy-complicating infections. That's the beauty of NIPT: A sample of maternal blood, a simple blood draw, is all that's needed to access the fetal genome and all the chromosomal information it contains.

????When cell-free DNA was discovered about 15 years ago, the science of genetics was not yet far enough along to make much practical use of it, but with the rapid advancement of genetic science over the past decade that's changed. Non-invasive tests can now piece together entire fetal genomes and mine that genetic information for indicators of various disorders and abnormalities that can lead to health problems later on -- things like sex chromosome abnormalities, Down syndrome, and a host of other developmental disorders. Initial trials have shown the tests to be so reliable that executives at more than one company vying for the lead in the nascent NIPT space -- companies that include Verinata (owned by Illumina (ILMN)), Sequenom (SQNM), Natera, Ariosa Diagnostics, and Ravgen -- believe their tests will become a standard, routine part of prenatal care in the next two or three years.

????"When you offset something like amniocentesis against NIPT -- which is as simple as taking a blood sample -- it becomes a no-brainer," says Vijay Kumar, a health care analyst and associate managing director at International Strategy and Investing Group. "But then the question becomes cost, and given the current health care environment it becomes a much tougher discussion."

????Indeed, it's cost more so than science holding NIPT testing back at this point. The tests remain relatively expensive, around $800 at the low end, and just less than $3,000 for the more expensive screening methods. Ongoing litigation between Sequenom and two other players in the space -- Natera and Ariosa Diagnostics -- has created some confusion as to who really owns what technology (not to mention some increased expense for all parties). And the technology is so new that insurers, though cognizant of the potential preventative health benefits of NIPT, have not yet determined exactly whether or how they will reimburse for the tests.