Parents should know “savior baby” not realistic in most cases

see Savior siblings and Fanconi anemia: analysis of success rates from the family’s perspective

When a child is diagnosed with Fanconi anemia (FA), a rare genetic syndrome that results in bone marrow failure and a predisposition to cancer, the only option for treatment has been a genetically matched stem cell transplant. When neither parent is a genetic match, some families opt to try to conceive a “savior” sibling using in vitro fertilization (IVF) of a genetically matched embryo. But little information about the chances of success using this technique has been available. Now a research team from Barcelona, Spain, reports only one baby born after 38 IVF attempts by seven families over 11 years. To avoid bias, the researchers followed all families at their clinic attempting the procedure. Of the 299 embryos generated by IVF, only 75 had the proper genetic match, and only a fraction of these were candidates for implantation. A total of 17 transferred embryos resulted in five pregnancies but only one birth, for a success rate of 2.6%. The average age of women attempting the procedure was close to 40, given that children are generally not diagnosed with FA until age 7. The researchers suggest that advanced maternal age combined with an already low statistical chance of identifying a matched embryo make conceiving a “savior baby” unrealistic. Parents should be informed of these low chances, the authors state, given the emotional and economic costs of IVF. However, recent scientific and medical advances in transplantation and gene therapy may someday offer families superior treatment options. —Karyn Hede, News Editor

First diagnosis of duchenne muscular dystrophy via a noninvasive prenatal test

see Haplotype-based approach for noninvasive prenatal tests of Duchenne muscular dystrophy using cell-free fetal DNA in maternal plasma

A research team based in Shanghai, China, has for the first time successfully diagnosed the most common form of muscular dystrophy using noninvasive prenatal testing (NIPT). Duchenne muscular dystrophy (DMD) is inherited via the X chromosome and affects 1 in 3,600 to 6,000 boys. The researchers used a technique they developed to recover, in a single step, the fetal genotype and both parental sequences from DNA in maternal blood plasma. Using this approach, they accurately predicted the mutation status of the fetus in eight pregnant women known to be DMD carriers. The tests showed that three of the fetuses were girls, two of whom did not inherit the DMD mutation. All five of the male fetuses were positive for the DMD trait. The results were confirmed by amniocentesis. Prior to this study, the researchers had shown that the technique effectively identified several autosomal recessive disorders, including congenital adrenal hyperplasia, maple syrup urine disease, and congenital deafness. However, no one had used NIPT to noninvasively predict the fetal mutation status in an X-linked disease. The test is not yet ready for routine clinical use, but the ability to diagnose common genetic disorders noninvasively early in pregnancy is sure to have important implications, both medical and ethical. —Karyn Hede, News Editor