Caroline Rodgers, whose ideas I blogged about yesterday, wrote to me about lack of research on the possibility that prenatal ultrasound causes autism:

I have heard confidentially that applications for funding of prenatal ultrasound studies (not specifically investigating autism) have been repeatedly denied over the years — which helps explain the great paucity of safety studies, especially since the early ’90s, when the FDA approved an allowable eightfold increase in acoustic output. As recently as this year, funding was denied an ambitious, multi-site study that would have investigated if there was a relationship between ultrasound and autism.

In 2006 when Yale neuroscientist Pasko Rakic announced the results of his study that found prenatal ultrasound interrupted neuronal migration in mice in a way that was consistent with the brains of autopsied autistics, I was surprised that several scientists, including Rakic, did their best to downplay the results. At the time, Rakic was one of many of Autism Speaks’s scientific advisors.

I have spoken with various people throughout the NIH about my concerns [about ultrasound]. They all pointed to various large studies they believe are investigating ultrasound as a possible environmental cause of autism — most recently, the National Children’s Study and EARLI, but when I tracked down the study designs, it turned out that ultrasound is not being studied.

In a report at the time Rakic’s study was published, he indeed downplayed the results:

Dr. Pasko Rakic, chairman of the Yale department of neurobiology and leader of the study, was quick to offer parents reassurance about the safety of ultrasound — done for the proper reasons — in human pregnancies.

“If I had a daughter and she was pregnant, I would recommend she had it for medical reasons,” Rakic said.

Another researcher agreed:

“I couldn’t agree with him more,” said Dr. Joshua Copel, a professor of obstetrics, gynecology and reproductive sciences at Yale and spokesman for the American College of Obstetrics and Gynecology (ACOG). He was not involved in the study. . .

The researchers noted that mice are very different from humans, so the results of their study must be interpreted with caution.

“The forms of migration [of brain cells] and the timing of migration differ in primates like humans than in mice,” Copel said. “In humans, there is a much longer period in which neurons [nerve cells] are migrating.”

Does that sound “very different”?

I blogged earlier about Caroline Rodgers’s idea that prenatal ultrasound may cause autism. She believes this idea isn’t getting the attention it deserves.

Recently she wrote to the head of Health and Human Services:

The latest autism prevalence figures released in December showed that while the overall autism rate increased more than 50% in the four years ending in 2006, there were significant differences across ethnic groups. White women had a much higher incidence of autism among their children than Black or Hispanic women. White mothers had 9.9 autistic children per 1,000, versus Black mothers who had 7.2 and Hispanic mothers who had 5.9.

There were also geographic differences. Among the 10 states with monitored sites, Alabama and Florida had the lowest autism rates, with averages of 4.2 and 4.6 per 1,000, respectively — far lower than the two states with the highest autism rates, Arizona and Missouri, which tied at 12.1 per 1,000. One interesting apparent statistical anomaly occurred among Alabama’s Hispanic population, which had a 68% decrease in autism while the overall national increase was 57%. In trying to understand why Alabama Hispanics had such a decrease in autism, I searched for evidence of public health policy changes. What I found was a surprise: according to a CDC multi-state surveillance report, Alabama and Florida were two of three states that had cutbacks in Medicaid funding for prenatal care during the time mothers in the study were pregnant. (The third state, West Virginia, was not among those monitored for autism in the latest study.)

Digging deeper, I turned up a CDC report on the timing of entry into prenatal care. The report showed that although most women started prenatal care in the first trimester, the percentages of both Black and Hispanic women who lacked early (first trimester) prenatal care were nearly twice that of White women . . . Over the span of the 10-year study, more women [in] all ethnic groups received early prenatal care, but the 2-to-1 ratio remained the same. . . .
Taken together, these three CDC reports tell a disturbing story: as more women . . . received more early prenatal care, the autism rate among their children increased, with those women receiving the most early prenatal care having the highest percentage of autistic children. . . .

A rigorous UC Davis study, published in January, of California children born between 1996 and 2000 identified 10 autism clusters . . . Highly educated women were much more likely to have children diagnosed with autism than parents who did not finish high school. In six of the clusters, the rate was as high as 4 to 1. Returning to the CDC Entry into Prenatal Care report, it is striking to note that in 1997 only 8.5% of pregnant women with some college education had delayed prenatal care, versus 29.9% of women who were not high school graduates — further [linking] early prenatal care [and] autism.

A study published in November on prenatal ultrasound trends from 1995-2006 found that the odds of a woman receiving an ultrasound during a prenatal visit nearly doubled over [those] 10 years. . . . The geographical and ethnic differences . . . dovetail with many of the geographical and ethnic differences found in the latest autism prevalence report. For instance, Southern women were 40% less likely to receive an ultrasound during a prenatal visit than Northeastern women, which could help explain why Florida and Alabama had the lowest autism rates among the states monitored. Also, Hispanics, who had the lowest overall autism prevalence rates in both the 2004 and 2006 CDC reports, were 20% less likely to receive an ultrasound during a prenatal than White women.

Not all the statistics available in these reports support the idea that prenatal ultrasound is causing autism. For instance, Southern states such as Georgia and North Carolina did not have low autism rates, but [perhaps this is because] the ultrasound trends study did not take into account “keepsake” ultrasound . . .

She also notes that a study by Yale neuroscientist Pasko Rakic “found that prenatal ultrasound disturbed neuronal migration in mice.”

Here is the broad argument. 1. Autism is correlated with wealth. It is absurd that autism causes wealth; it is unlikely that both are caused by something else. Thus this correlation makes it plausible that autism is caused by something that rich people have more of than poor people. Obviously rich people have more prenatal ultrasound. 2. A localized decrease in autism happened at the same time autism almost everywhere was increasing. At the same place and time prenatal ultrasound screening surely declined. This correlation is very difficult to explain with other ideas about what causes autism. Dozens of things (e.g., genes, diagnostic criteria) previously proposed as explanations of autism remained roughly constant at the same time as the decrease. 3. The mice data make the linkage considerably more plausible, assuming (a) the ultrasound dosage was reasonable and (b) humans with autism have unusual neural wiring that resembles the changes seen in the mice.

The full letter is on her blog. An article by Rodgers about this