In a normal pregnancy, most women get an ultrasound once or twice so doctors can check the fetus for abnormalities and curious parents can learn if they should paint the nursery pink or blue.
Zika, however, is changing the rules.
The Centers for Disease Control and Prevention is recommending that women who may have been exposed to the virus get an ultrasound every three or four weeks. This worries researchers who have studied the effects of prenatal ultrasounds in animals and believe they can cause changes in the developing brain and may be responsible for the troubling rise of autism, the mental disorder that has more than doubled in the U.S. in recent years.
In the most recent study to suggest a link between ultrasounds and autism, Sara Webb and other researchers at the University of Washington examined the records of 2,644 children diagnosed with autism spectrum disorder. Those children with autism and a genetic error, who were also exposed to ultrasound in the first trimester, had more severe symptoms of autism than the children not exposed to ultrasound. They found no link with behavior and ultrasound in the second and third trimesters.
While some doctors said the study's limitations raised questions about its conclusions, Webb, an associate professor at the University of Washington, said the findings support the Food and Drug Administration's position on ultrasounds, which is that they should be performed only when medically necessary. Monitoring a low-risk pregnancy with ultrasound in the first trimester might not qualify, Webb noted.
“It’s worthwhile to consider why a first-trimester ultrasound is being done. The pictures do provide some bonding, but if it is not medically necessary, you should wait until later in the pregnancy," she said.
The first fetal ultrasound was conducted in 1958 by a Scottish doctor named Ian Donald. He produced a grainy image that few today could identify as a human head, but within a decade, other doctors were using the technology contained in a machine so tall and bulky that some people called it the "Dinosaurograph." (Its actual name was the Diasonograph.)
By the late 1970s, sonography had evolved to smaller and sleeker machines, enabling their universal use. After several large studies found no differences in children whose mothers had ultrasounds and those who didn't, the FDA approved a higher frequency in 1992 -- from 94 milliwatts per square centimeter to 720, an eight-fold increase. There have been no large-scale controlled studies since then, but the use of ultrasounds has exploded.
In 2014, a Wall Street Journal investigation found that the average woman has five during a single pregnancy, a 92 percent increase from 2004. Women in high-risk pregnancies may have them more frequently.
And they are ever more attractive to expectant couples because of improved clarity and increased availability.
Ultrasound as entertainment
At boutiques across the country, pregnant women can obtain ultrasounds without a doctor's order. Such procedures, sometimes called "vanity ultrasounds" or "recreational sonography," are not covered by insurance.
Fetal Studio, with locations in Sandy and Lehi, Utah, is dubbed an "entertainment service" on its Facebook page. It offers 2D, 3D and 4D sonography packages, some of which include a DVD and CD of the baby.
Most medical professionals discourage the use of ultrasound boutiques, where both the training of sonographers and the equipment itself may not meet medical standards. (Only four states -- Oregon, New Hampshire, New Mexico and North Dakota -- require medical sonographers to be licensed.)
Some of these businesses also encourage multiple visits, and offer ultrasounds at any time during the pregnancy, even in the first trimester, when the risk to the fetus is thought to be highest.
Fetal Studio, which did not respond to requests for an interview, offers discounts for return visits and a free follow-up if the baby isn't in the "right" position for the first ultrasound, according to its website.
Margulis, the mother of four, became concerned about the risks of ultrasound after researching studies that suggest a correlation between autism and ultrasound, as well as one that found no significant benefit to the procedure.
“I would say there’s no good reason to get an ultrasound in the first trimester and considering we have such a huge problem right now with the rise in autism, there are good reasons to avoid it,” Margulis said.
“We have more brain damage among children than we’ve ever seen. Anything that might be contributing to the autism epidemic is something we must take seriously. Even if it’s only just possible that ultrasounds may be one of the contributing factors, we must pay attention,” she said.
Just because a practice is a standard of care today doesn’t mean it will be tomorrow, Margulis said, noting that previously common practices, such as X-raying a pregnant woman’s stomach or prescribing diethylstilbestrol to prevent miscarriages, were later shown to have devastating effects.
She notes that Williams Obstetrics, the classic textbook for obstetricians, does not recommend routine ultrasounds, saying they should be performed "only with a valid medical indication and with the lowest possible exposure setting to gain necessary information."
The Society of Medical Diagnostic Sonography says ultrasounds are safe and beneficial "when performed for a medical purpose and by a person with appropriate education, training, experience, and certification."
The American College of Obstetricians and Gynecologists says there is no "reliable evidence" that ultrasounds can cause birth defects, childhood cancer or developmental problems, but adds a caveat:
“However, it is possible that effects could be identified in the future. For this reason, it is recommended that ultrasound exams be performed only for medical reasons by qualified health care providers,” the ACOG website says.
“The risks are basically theoretical at this point,” said Dr. Sarah Horvath, an ob-gyn in Philadelphia who says numerous studies have shown no harm from sonography, including one that followed 8,000 babies into adulthood. “The only association found with all those children was a possible association for boys to not be right handed."
“What we do know is that ultrasounds should be as short as they can be, at the lowest possible setting, to achieve what is medically necessary," Horvath said.
But Dr. Manuel Casanova, a neurologist and professor of biomedical sciences at the Greenville campus of the University of South Carolina School of Medicine, said even though the “medically necessary” mantra is often repeated, “practically nobody adheres to this.”
“When my daughter went for the first time to the ob-gyn, she was asked if she wanted to see a photograph of her baby. Well, who can say no to that? But this is not a valid reason for an ultrasound. And when the ultrasound was finished, she was asked, ‘Would you like to see anything else?’” Casanova said.
How ultrasounds work
To get those remarkable pictures, a sonographer uses one of several techniques.
In a transabdominal ultrasound, the most common, the sonographer applies gel to woman's stomach, and moves a wand, called a transducer, over it. The transducer emits sound waves that bounce off the fetus and create the image shown on a computer screen.
A transvaginal ultrasound works the same way, but the transducer is inserted into the vagina.
A Doppler ultrasound is usually used in the third trimester to inspect the baby's blood vessels.
Three-dimensional ultrasound joins several 2D images to create a 3D photograph, and 4-D shows movement in a video.
The potential risk to the fetus comes from the heat and pressure of the procedure.
"Ultrasound waves can heat the tissues slightly. In some cases, it can also produce small pockets of gas in body fluids or tissues (cavitation). The long-term consequences of these effects are still unknown," the FDA says.
The fetus is particularly vulnerable in the first 12 weeks of life, said Webb, of the University of Washington. “The neurons that form the brain are being developed, and they form in one area of the central nervous system and then have to travel to other places,” she said.
“Potentially, if you heat up the tissue and put pressure on it (while this is happening), what’s going to happen to those neurons? Mouse models suggest that they may end up in the wrong place," she said.
Casanova, the University of South Carolina neurologist, has hypothesized that prolonged sound waves are causing atypical cell division and migration. He notes that the FDA approved ultrasound to treat bone fractures because it increases cell division.
He believes there is sufficient evidence in studies among humans to suggest an association between ultrasounds and dyslexia and growth retardation. Animal studies support a link between hyperactivity, and learning and behavior abnormalities, he said.
“But 99 percent of the public is not aware of this,” Casanova said. As an example, he cites the trend of ultrasound baby showers where party guests take turns using the transducer to look for the baby.
People can even buy their own machines to use at home.
“The FDA provides only a warning. It’s buyer beware. Unfortunately, buyers are not being very astute," Casanova said.
In response to the University of Washington study, the Texas-based Society of Diagnostic Medical Sonography issued a statement expressing concern that women might forego or delay medically necessary procedures because of research that was limited in scope.
"We encourage pregnant women to talk with their physician if they have questions or concerns. However, they should not avoid having medically necessary examinations using ultrasound during pregnancy based on this limited study," the group's president, Sheryl Goss, said.
The March of Dimes, the famed nonprofit that works to improve babies' health, also maintains that ultrasound is safe when performed by a health-care provider, and notes that its benefits include diagnosing an ectopic pregnancy or confirming multiple babies.
And first-trimester ultrasounds have been a boon to the pro-life movement, which uses the images to help convince pregnant women to keep their babies. "A mother looking at an ultrasound of her 10- or 12-week-old child will know that this is no mere clump of cells, bit of tissue, or tumor," Howard Slugh wrote last year for National Review.
Even if a link to autism is not ultimately proven, Margulis argues that there are other reasons to decline ultrasounds, such as the risk of false positives and the resulting stress, and images that result in C-sections that may be unnecessary.
“If you do get an ultrasound, make sure you do it at the least possible exposure for the least amount of time. Don’t linger and look at your baby for an hour because you may be exposing your baby to harm," Margulis said.
You can also check to see if the person performing your ultrasound is certified by the American Registry for Diagnostic Medical Sonography. A search service is provided on the group's website, ardms.org; all you need is the sonographer's last name.