Next to delivery, ultrasound scans are one of the most anticipated milestones of a pregnancy. For many, seeing that black-and-white blob is the moment their impending parenthood starts to feel real. But how many ultrasounds will you get over the next nine months? And is there such a thing as too many?
Ultrasound technicians create an image of your baby by pointing sound waves at soft tissues in your body using a handheld probe that is either inserted into your vagina or a transducer that is rubbed over your belly. The waves that bounce back are translated into a picture by the imaging technology. Midwives and doctors use those images to monitor things like how the baby is growing or to look at the health of the uterus, says Jasmin Tecson, a registered midwife who has been practising for almost 13 years with Sages-Femmes Rouge Valley Midwives in Scarborough, Ont.
While there are no official recommendations for how many ultrasounds should be performed in a pregnancy, the Society of Obstetricians and Gynaecologists of Canada (SOGC) regularly reviews the research and issues guidelines for care providers, says OB/GYN Howard Berger, head of maternal fetal medicine and obstetric ultrasound at St. Michael’s Hospital in Toronto. When you’re newly pregnant, you’ll typically be offered an initial dating ultrasound between eight and 13 weeks. It’s used to confirm your pregnancy, establish a due date and eliminate surprises when it comes to how many babies are growing in there.
This may be done separately or at the same time as a scan offered at 11-13 weeks as part of the optional screening for trisomy 21 (or Down syndrome). In this ultrasound, the fetus’s neck thickness is measured.
A second ultrasound (or third) ultrasound is usually done at 18 to 20 weeks to review the baby’s anatomy and rule out abnormalities. It’s also when you can find out the gender, if you care to know. In a typical, low-risk pregnancy, those two scans might be all you ever need—much to the surprise of many first-time parents who assume they’ll get another peek later, when the baby looks more like, well, a baby.
Some doctors may order a routine growth scan in the third trimester, but that depends on the pregnancy, says Berger. If your due date passes, an ultrasound to assess amniotic fluid volume and fetal health is often performed.
Most parents are thrilled to get those first grainy pictures. But what if you’re a less-info-equals-less-worry type of person? Sometimes an ultrasound raises more questions than it can answer. When Allison Crinkley of Sackville, N.B., was pregnant with the first of her two daughters, an early ultrasound showed a shadow on the baby’s heart. “At the follow-up ultrasound, that was gone. But then they found another blip, something to do with the baby’s brain,” she says. Fortunately, a follow-up ultrasound determined it was nothing to worry about. “But after that, I was on edge about everything,” says Crinkley. Her daughter was born early at 35 weeks, and while her doctors don’t know what caused the premature arrival, Crinkley believes her stress levels contributed to it.
Here's how ultrasounds actually work Skipping ultrasounds altogether is less common, but it is sometimes possible. “In a healthy, low-risk pregnancy,” says Tecson, “it’s not unreasonable to weigh the risks and benefits. A due date could be set based on the last menstrual period, for example,” she says. If there’s something a doctor or midwife needs to monitor (concerns about the amniotic fluid or the size of the baby, for example), you can expect more-frequent scans. “It’s the best window into fetal well-being we have,” says Berger.
What if your mother-in-law is back from Florida and pushing for another ultrasound so that she can tag along? “I can’t justify giving a requisition for that,” says Tecson. “[Ultrasounds should be used] only when we have a clinical question to answer—not for visiting with the baby,” she says.
Some expectant parents find a 3D or 4D ultrasound business where they can pay for more pictures or videos, but both Health Canada and the SOGC have issued warnings against what they call “keepsake” or “entertainment” ultrasounds. Scans are supposed to be vetted by a radiologist or other primary caregiver before being shared with patients, but sometimes things come up.
“A parent might get unrealistically reassured,” says Berger, “or there could be unnecessary stress.”
There are also some concerns about additional exposure to the sound waves.
“We know that ultrasound energy focused on cells causes heat and vibration,” Tecson says. “What we don’t know is what that disruption could mean at a genetic level in the long-term”—particularly for female babies who are already carrying half the genetic material for any future grandkids.
While Berger is less concerned with the impact of the sound waves—“The energy required to obtain these images is very, very low,” he says—both he and Tecson worry about the interpretation of results.
Still, it can be tempting to ask or pay for more frequent scans as a way of coping with the anxiety that often accompanies even the healthiest of pregnancies. Berger feels it’s important not to use ultrasounds as a Band-aid, but to address the underlying issues causing a patient’s anxiety, especially since prenatal anxiety can be a precursor to postpartum depression.
Sometimes, though, the reassurance that ultrasounds provide is something no one would deny an expectant parent. For Kristina Askandar, a mother of two from Brampton, Ont., weekly ultrasounds at the Subsequent Pregnancy Program at Sunnybrook Hospital in Toronto were crucial because she’d experienced pregnancy loss before. Without those checks, Askandar says she would have been in a constant state of anxiety. On the hard days, “I knew I just had to hang on until the next scan,” she says.
Ultimately, there isn’t an ideal number of ultrasounds to have during a pregnancy—only you and your doctor or midwife can decide what’s best for you and your baby. If you think your next ultrasound appointment might be your last, you could pull out your phone and take a video of the technician’s screen (ask permission first). That way you and your family can coo over the images whenever you want.
Did you know?
There are growing concerns about home Doppler machines, which let you listen to the baby’s heartbeat. There’s a bill before Parliament in the UK to regulate sales of home Dopplers, after several widely shared stories of parents who were improperly reassured by a Doppler and subsequently experienced a stillbirth.