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anemia
Prenatal testing curbs some genetic diseases
Feb 18th
Some of mankind's most devastating inherited diseases appear to be declining, and a few have nearly disappeared, because more people are using genetic testing to decide whether to have children.
Births of babies with cystic fibrosis, Tay-Sachs and other less familiar disorders seem to have dropped since testing came into wider use, The Associated Press found from interviews with numerous geneticists and other experts and a review of the limited research available.
Now, more women are being tested as part of routine prenatal care, and many end pregnancies when diseases are found. One study in California found that prenatal screening reduced by half the number of babies born with the severest form of cystic fibrosis because many parents chose abortion.
More couples with no family history of inherited diseases are getting tested before starting families to see if they carry mutations that put a baby at risk. And a growing number are screening embryos and using only those without problem genes.
The cost of testing is falling, and the number of companies offering it is rising. A 2008 federal law banning gene-based discrimination by insurers and employers has eased fears.
Genetic testing pushes hot-button issues: abortion, embryo destruction and worries about eugenics - selective breeding to rid a population of unwanted traits.
Some diseases - sickle cell, cystic fibrosis, Tay-Sachs, thalassemia, spinal muscle atrophy - occur when people inherit two bad genes, one from each parent. The genes can pass quietly for generations until two carriers mate; then children have a one-in-four chance of getting the disease.
Comparisons to couples not given prenatal screening suggested that screening had cut births of babies with severe disease in half, researchers reported at a genetics conference in 2008. Studies in Canada, Italy, Australia and in Europe also found that cases dropped after screening began.
Gene testing hasn't led to declines in all diseases. Sickle cell, a blood disorder that causes anemia and pain and raises the risk of stroke, has not dropped. It mostly afflicts blacks; gene carriers are said to have sickle cell "trait," which sounds harmless.
"Now we're actually learning that it's not as benign as we thought it was," and that carriers have higher risks for certain medical problems, said Dr. Lanetta Jordan, a Florida physician and chief medical officer of the Sickle Cell Disease Association of America.
Newborn screening is finding more sickle cell carriers and cases, but this doesn't seem to affect parents' future family plans, Jordan said.
The number of fertility treatments that include embryo screening has been on the rise in recent years, with nearly 5,200 screenings in 2006, according to the Society for Assisted Reproductive Technology. Carrier testing also is rising. A California company, Counsyl, sells a $349 saliva test for genes for more than 100 inherited disorders. Several thousand people used it over the last year, the company reports.
Eliminating disease is a noble goal but also "should give us pause," Lerner, the Columbia historian, wrote recently in the New England Journal of Medicine.
"If a society is so willing to screen aggressively to find these genes and then to potentially to have to abort the fetuses, what does that say about the value of the lives of those people living with the diseases?" he asked.
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Mom’s anemia may raise schizophrenia risk in offspring
Feb 10th
Children of mothers who had been diagnosed with anemia during pregnancy, most likely due to iron deficiency, had a significantly elevated risk of developing the mental disorder, the study's lead researcher Dr. Holger Srensen of the University Hospital of Copenhagen in Demark, told Reuters Health by email.
Iron is necessary for the production of hemoglobin, a protein that distributes oxygen throughout the body. Because a pregnant woman carries an additional set of organs and tissues -- and almost 50 percent more blood -- she needs extra iron to ensure that enough oxygen gets around.
"We speculate that maternal iron deficiency may disrupt essential pathways that affect the delivery of oxygen and nutrients to the fetus," Srensen said. Earlier research has suggested that a failure to meet the iron demands of a developing brain might heighten a child's vulnerability to disorders such as schizophrenia.
To further investigate this potential link, Srensen and colleagues analyzed the psychiatric outcomes of a large group of Danish children born between 1978 and 1998 -- the biggest cohort in which the relationship has been examined. Each child was followed from age 10 until the onset of schizophrenia, death or the study's closure on December 31, 2008.
Among 1,115,752 newborns, 17,940 (1.6 percent) were exposed to anemia in the womb. A total of 3,422 -- including 41 from the exposed group -- went on to develop schizophrenia, according to the report published in the journal Schizophrenia Bulletin.
After accounting for differences between the two groups and other relevant factors, including the parents' ages and history of mental illness, exposure to anemia in the womb was associated with a 60 percent increased risk of schizophrenia in offspring during the 20 years of the study.
The researchers further concluded that 0.58 percent of schizophrenia cases (a total of about 20 diagnoses) could have been prevented had there been no cases of anemia among the mothers.
These figures may be underestimates of anemia's true impact, according to Srensen and colleagues. It is possible that some pregnant women received anemia diagnoses and treatment from general practitioners outside the hospital, and therefore outside of the Danish registry used for the study.
Schizophrenia diagnoses may have been under reported as well. Even the oldest cohort members were only followed until age 30. Rates of schizophrenia peak around age 22 or 23, noted Srensen, so the study "may have missed around 50 percent of cases with a later onset."
The researchers also lacked access to the women's precise hemoglobin levels, which prevented assessment of the relative severity of anemia.
Despite its unresolved relationship with schizophrenia, prevention and treatment of maternal anemia remains straightforward. "Checking for iron-deficiency anemia (or anemia from other causes), and correcting a deficit," Srensen said, "is relatively simple in a clinical setting."
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