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To shield any future children from the fear she harbors of getting breast cancer, Katie Dowdy underwent a controversial procedure to select embryos of hers that were free of a genetic mutation linked to the disease.
为了不让孩子将来像自己一样害怕患上乳腺癌，凯蒂·道迪(Katie Dowdy)做了一项充满争议的检查，以挑选出不携带一种被认为与乳腺癌相关的基因突变的胚胎。
Deciding to have the procedure, called preimplantation genetic diagnosis, or PGD, wasn't easy, says Ms. Dowdy. Her husband initially 'worried about playing God,' she says. 'I thought, if I could have a healthy baby who doesn't have to worry about the same thing I did, why wouldn't I?' says the 34-year-old, who hasn't had cancer. The couple, who live in Castle Pines, Colo., now have two young girls, both born using PGD.
道迪说，决定做这项名叫“着床前遗传学诊断”（简称PGD）的检查并不是一个容易的过程。她说，起初丈夫“担心自己是在扮演上帝的角色”。现年34岁、没有得过癌症的她说：“我想，如果我能有一个健康的孩子，不需要担心我所担心的事情，那我为什么不做呢？”夫妇俩家住科罗拉多州派恩堡，现有两个年幼的女儿，都是在做了PGD之后出生的。
Preimplantation genetic diagnosis has long been available during IVF, or in vitro fertilization, to eliminate the risk of passing on severe disorders such as spinal muscular atrophy and cystic fibrosis. Now, fertility clinics say they are seeing a small but increasing number of women choosing PGD to avoid giving birth to children who carry mutations in the BRCA genes, which increase the risk for breast and other cancers.
防范于未然着床前遗传学诊断(PGD)检查胚胎有没有某种可能会从父母身上遗传而来的遗传缺陷。以下是PGD检查的一些疾病：
'It's on the rise because more people are becoming aware that there's a genetic component to breast cancer,' says Mark Hughes, founder of Genesis Genetics, in Plymouth, Mich., which offers reproductive-genetics-diagnosis services to fertility clinics nationwide.
囊性纤维化
Critics fear genetically vetting embryos can be used to create so-called designer babies. Embryos with the gene mutation may be discarded, which some critics also oppose. Gender selection is one form of embryo-testing that stirs ethical questions. Some clinics will agree to select for a specific sex only for health reasons -- to avoid a disease such as hemophilia, for example, which typically is passed only to boys. Opponents of PGD for breast cancer also say that having a BRCA-gene mutation doesn't mean a person will necessarily get the disease and that there are options for detecting and treating the cancer.
血友病
A parent with a mutation on the BRCA1 or BRCA2 genes has a 50-50 chance of transmitting it to the next generation. Between 45% and 65% of women with the mutations are expected to be diagnosed with breast cancer by age 70, according to the National Cancer Institute. That compares with about 12% of women in the general population.
亨廷顿氏舞蹈症
BRCA mutations, which also increase the risk for ovarian, prostate and other cancers in men and women, are relatively rare, accounting for 5% to 10% of all breast cancers. Some women undergo prophylactic mastectomy to reduce their chances of getting the disease.
马方氏综合征
In Ms. Dowdy's family, the specter of breast cancer hovers. Her paternal grandmother died in 1979, five months before Ms. Dowdy was born. Several of her grandmother's sisters also got breast cancer. Ms. Dowdy's father had a genetic test and found he had inherited the BRCA1 mutation. When she was 27, a test showed Ms. Dowdy also had the mutation.
肌肉萎缩
After her aunt, who shares the same mutation, had a prophylactic mastectomy, Ms. Dowdy researched her options and learned about PGD. Ms. Dowdy says she and her husband had struggled to conceive. Figuring they would need fertility assistance, also doing PGD to avoid passing on the BRCA mutation seemed like an obvious precaution.
地中海贫血
The PGD process begins with standard IVF. After two weeks of hormonal stimulation, eggs are retrieved, fertilized and left to multiply for five days. Then a laboratory scrutinizes several cells, looking for gene mutations. The analysis isn't believed to harm the embryo. Embryos without BRCA mutations are earmarked for transfer into a woman's uterus.
黑蒙性白痴
Two of Ms. Dowdy's seven embryos were BRCA-mutation free. Both were transferred to her uterus. One implanted and grew to become a daughter, Reagan, born in 2010. Ms. Dowdy and her husband opted for PGD again to conceive another child, Mackenzie, born in March.
脊髓性肌萎缩
Only recently have some doctors started discussing PGD with women who have a breast-cancer mutation. More often, BRCA-positive women learn about the procedure on their own. 'We write about it in our newsletter and we've done webinars on it, but not everyone knows about it,' says Sue Friedman, executive director of Force, a nonprofit patient-support group focused on hereditary breast and ovarian cancers.
镰状细胞贫血
For women who have no trouble conceiving, the choice to do PGD involves the added hassle of fertility treatment. PGD can add about $6,000 to the price of IVF, which runs at least $10,000, depending on the clinic, plus thousands of dollars more for medications.
资料来源：纽约大学生殖中心(NYU Fertility Center)很久以来，在试管受精的操作过程中，都可以通过着床前遗传学诊断来消除将脊髓性肌萎缩、囊性纤维化等严重缺陷遗传下去的风险。而现在，据生殖医院说，数量不大但越来越多的女性都在选择做PGD以避免生下携带BRCA基因突变的孩子。BRCA基因突变会增加患乳腺癌和其他癌症的风险。
'It's by no means 100% [of eligible women] who are choosing to do it,' says William Schoolcraft, medical director of the Colorado Center for Reproductive Medicine in Lone Tree, Colo., and Ms. Dowdy's doctor. Dr. Schoolcraft says he has done about 10 PGD procedures to eliminate a BRCA mutation in the past three years. He has heard some patients say ' 'My grandma had it, my aunt had it, my mom had it. I want to stop this train.' Others have the attitude that if my baby turns out like me, so be it.'
密歇根州普利茅斯堡的Genesis Genetics为全国生殖医院提供生殖遗传学诊断服务。创始人马克·休斯(Mark Hughes)说：“之所以数量在上升，是因为越来越多的人懂得乳腺癌包含遗传成分。”
Even after an embryo selected through PGD is successfully implanted, some doctors recommend an amniocentesis or another prenatal test called CVS to make sure there isn't a BRCA-gene mutation.
批评者担心，经过遗传学检查的胚胎有可能被用于制造“定制婴儿”(designer baby)。含有基因突变的胚胎可能被抛弃，这也是一些批评者所反对的。性别选择是激起伦理争议的胚胎检查形式之一。一些医院只会同意出于健康原因而选择某个性别，比如说规避常常只遗传给男孩的血友病等。乳腺癌PGD反对者还说，携带BRCA基因突变并不意味着人一定会得这种病，而且乳腺癌的侦测和治疗还有其他方法。
'You have to think of it from the perspective of a woman whose life has been turned upside down by breast cancer and the guilt associated with choosing to have a baby that could have those same problems,' says James Grifo, director of the Division of Reproductive Endocrinology and Infertility at NYU Fertility Center.
携带BRCA1或BRCA2基因突变的父母有50%的概率将它遗传给下一代。根据国家癌症研究所(National Cancer Institute)数据，45%到65%携带这些突变的女性预计会在70岁之前被诊断出乳腺癌。相比之下，一般女性的这个概率在12%左右。
Bonnie Rochman
BRCA突变也会增加男性和女性罹患上卵巢癌、前列腺癌等癌症的风险。这类突变相对少见，占所有乳腺癌的5%到10%。有些女性通过做预防性乳房切除术来降低患乳腺癌的风险。
