The short version
- A typical Ontario pregnancy includes a dating scan, an optional nuchal translucency scan between 11 and 14 weeks, the anatomy scan at 18 to 20 weeks, and one or more third trimester scans if your provider orders them.
- Each scan needs a requisition from your physician, midwife or nurse practitioner. Bring it with your health card.
- Early scans usually need a full bladder. Later scans usually do not.
- The sonographer captures the images. A qualified physician interprets them and sends the report to your care provider, who reviews it with you.
- We perform obstetrical ultrasound six days a week at 115 Simcoe Street South, 3rd Floor, in downtown Oshawa.
Pregnancy ultrasound is the exam most people picture when they think of an ultrasound at all. It is also the one that generates the most questions at our front desk, because every scan in pregnancy has a different purpose, a different timing window, and different preparation.
This guide walks through the scans your care provider is likely to order, in the order they usually happen. It applies to patients across Oshawa, Whitby, Courtice, Bowmanville, Ajax and Pickering who are booked with us, and the general timing applies anywhere in Ontario. Your physician or midwife decides which scans you need. This is what each one is for.
The typical schedule
Scroll sideways to see the full table.
| Scan | When | Main purpose | Preparation |
|---|---|---|---|
| Dating scan | About 7 to 12 weeks | Confirm the pregnancy is in the uterus, count how many, check the heartbeat, set the due date. | Full bladder |
| Nuchal translucency | 11 weeks 2 days to 13 weeks 6 days | Measure fluid at the back of the baby's neck as part of first trimester screening. | Full bladder is often helpful |
| Anatomy scan | 18 to 20 weeks, sometimes up to 22 | Detailed check of the baby's organs, limbs, spine, brain and heart, plus the placenta and fluid. | Usually none |
| Third trimester growth or position | 28 weeks onward, as ordered | Baby's size and growth, position, placenta location, fluid volume. | Usually none |
The dating scan
Usually the first ultrasound of a pregnancy, ordered once a positive test has been confirmed and typically performed between about seven and twelve weeks. Despite the name, dating is only one of its jobs.
- Where the pregnancy is. The sonographer confirms the gestational sac is inside the uterus, which rules out an ectopic pregnancy.
- How many. Twins are usually identified at this stage, along with whether they share a placenta, which matters for how the pregnancy is monitored.
- The heartbeat. Cardiac activity is usually visible from around six weeks and is measured and recorded.
- The due date. The baby is measured from the top of the head to the bottom of the torso, the crown rump length. In the first trimester this measurement is accurate to within a few days, which is why an early ultrasound sets the due date that the rest of the pregnancy is planned around, even if it differs from the date calculated from your last period.
Very early in pregnancy, before about eight weeks, a transvaginal approach may be needed to see clearly. If that applies to you, the sonographer will explain it, a signed consent form is required, and you can download it in advance from our forms page.
Bleeding or pain in early pregnancy? Contact your care provider or go to the emergency department. Do not wait for a routine appointment. An urgent requisition is handled differently from a scheduled scan, so tell us at booking if your provider marked yours as urgent.
Nuchal translucency, 11 to 14 weeks
Ontario offers prenatal screening to every pregnant patient. In the first trimester, the standard option is enhanced first trimester screening, which combines a blood test with a specific ultrasound measurement: the nuchal translucency, a thin layer of fluid at the back of the baby's neck. Together they estimate the chance of certain chromosomal conditions. The screen does not diagnose anything; it identifies who may benefit from further testing.
The measurement is only valid inside a narrow window, from 11 weeks and 2 days to 13 weeks and 6 days, and the baby has to be in the right position. That is why this scan sometimes takes longer than expected, and occasionally requires a short walk and a second try. During the same scan the sonographer confirms the heartbeat, measures the baby again, and looks at the early anatomy that is visible at this stage.
Screening is your choice. Your care provider will discuss whether you want it, and if you do, they will time the requisition and the bloodwork so both fall within the window. If you choose not to screen, you will still usually have a dating scan and the anatomy scan.
The 18 to 20 week anatomy scan
This is the longest and most detailed scan of the pregnancy, sometimes called the morphology scan or, informally, the twenty week scan. It usually takes 30 to 45 minutes, and longer if the baby is not cooperating.
The sonographer works through a structured checklist that covers the brain and skull, face and lip, spine, heart and its four chambers and major vessels, chest and lungs, stomach, kidneys and bladder, abdominal wall, arms and legs, hands and feet. They also assess the placenta and where it sits relative to the cervix, the umbilical cord, the amount of amniotic fluid, and the baby's growth measurements. If you are carrying more than one baby, every step is repeated for each.
Two things are worth knowing in advance. First, the baby's position sometimes hides a view that has to be documented, and the answer is a short repeat visit a few weeks later, not a cause for alarm. Second, this is the scan where the baby's sex is usually visible. Tell the sonographer at the start whether you want to know. They will do their best, but it is not the purpose of the exam and cannot be guaranteed.
Third trimester scans
Not every pregnancy has a third trimester ultrasound. Your provider orders one when there is a specific question, and the most common ones are:
- Growth. If the baby is measuring small or large on the tape measure, or you have a condition like diabetes or high blood pressure, a growth scan estimates the baby's weight and tracks it over time.
- Position. From about 36 weeks, confirming whether the baby is head down, breech or transverse helps plan the birth.
- Placenta. If the placenta was low at the anatomy scan, a follow up confirms whether it has moved up, which it usually has.
- Fluid. Too little or too much amniotic fluid changes how the pregnancy is monitored.
Third trimester scans are usually shorter and do not need a full bladder. Lying flat can be uncomfortable late in pregnancy, so tell the sonographer if you need to shift position or take a break.
How to prepare
- Get the requisition
Your physician, midwife or nurse practitioner completes an ultrasound requisition stating which scan is needed and your dates. They can fax it to us at +1 (289) 731-2606 or give you a copy to bring.
- Book inside the window
Timing matters most for the nuchal translucency scan. Book as soon as you have the requisition so we can find a date in the right week.
- Follow the bladder instructions
For early scans, drink about two to three glasses of water in the hour before your appointment and do not empty your bladder. For scans after 18 weeks, this is usually not needed. We confirm your instructions when you book.
- Bring your health card
A valid Ontario health card, your requisition if you have a paper copy, and any consent form that applies.
- Dress for it
A two piece outfit is easiest. You will be asked to expose your abdomen and will be draped for privacy.
What the visit is like
You check in at reception on the third floor of 115 Simcoe Street South, and we confirm your details and the provider who will receive your report. In the exam room, warm gel is applied to your abdomen and the sonographer moves the probe across it while watching the screen. The room is dimmed so fine detail is visible. You may be asked to roll onto one side, take a deep breath, or wait a moment while the baby moves. Most patients describe it as comfortable, apart from the full bladder early on.
The sonographer will often point out the baby, the heartbeat and the limbs, and you can usually see the screen. What they cannot do is interpret the images or discuss findings. That is the physician's role, and it is the same rule at every imaging clinic in Ontario. Read more in our guide to what to expect at your ultrasound appointment.
Results and what we can share
A qualified physician reviews your images and issues a report to the provider named on your requisition. Book a follow up with them to go through it. If a scan is marked urgent, it is flagged accordingly. If your provider has asked for the images themselves, they can request them through our office.
One honest note about printed pictures. Our priority during a diagnostic scan is capturing the images your provider needs, and we keep the exam to the length required for that. If a clear image of the baby's face or profile comes up during the scan, the sonographer will often print it for you, but this cannot be promised and we do not extend scans for keepsake images.
Booking a pregnancy ultrasound in Oshawa
We offer dating, nuchal translucency, 18 to 20 week anatomy and third trimester scans at 115 Simcoe Street South, 3rd Floor, in downtown Oshawa. We are open Monday to Friday from 9:00 AM to 6:00 PM and Saturday from 10:00 AM to 4:00 PM, which helps if a weekday appointment is hard to arrange. Call +1 (289) 481-0263 or request an appointment online, and have your requisition and your dates ready. See the obstetrical ultrasound service page for the full list of exams.
Common questions
Do I need a requisition for a pregnancy ultrasound?
Yes. Every diagnostic ultrasound in Ontario, including obstetrical scans, requires a requisition from a physician, midwife or nurse practitioner. Bring it with your valid Ontario health card, or ask your provider to fax it to us at +1 (289) 731-2606.
Can my partner or a support person come into the room?
Yes. One support person is welcome in the exam room. Please let us know when you book. Young children are best left with a caregiver, since exams need the sonographer's full concentration.
Will the sonographer tell me the baby's sex?
If you would like to know and the baby is positioned well, the sonographer will usually try to tell you at the 18 to 20 week scan, but it is never guaranteed and is not the purpose of the exam. Tell the sonographer at the start of the appointment if you do not want to know.
Is ultrasound safe in pregnancy?
Diagnostic ultrasound uses sound waves, not radiation, and has been used in pregnancy for decades with an excellent safety record. Scans are performed only when medically indicated and kept to the length needed to answer the clinical question.
Do you offer 3D, 4D or keepsake scans?
No. We perform diagnostic obstetrical ultrasound ordered by your care provider and covered by OHIP. We do not offer entertainment or keepsake imaging.
Do I need a full bladder?
For early pregnancy scans, usually yes. A full bladder improves the view of the uterus. For the 18 to 20 week scan and later, a full bladder is generally not required. We confirm the exact instructions with you when you book.
What if the scan finds something?
The report goes to your care provider, who will review it with you and arrange any follow up. Some findings simply mean a repeat scan in a few weeks for a better view. Our staff are not able to discuss findings during the appointment.
This article is general information only and does not replace medical advice. Please speak with your physician or healthcare provider about your own health concerns. Imaging results are interpreted by qualified professionals and sent to your referring physician.