Preparing for a pregnancy ultrasound is straightforward, but the specific steps depend on how far along you are. The single most important thing: if you’re less than 14 to 16 weeks pregnant, you’ll need to drink 28 to 32 ounces of water and finish it about one hour before your appointment. After 16 weeks, you can typically show up with an empty bladder. Beyond that, a few small choices about clothing and skin care can make the experience smoother.
Why a Full Bladder Matters Early On
In early pregnancy, the uterus still sits low in the pelvis, tucked behind the bladder and bowel. A full bladder pushes the uterus upward and moves loops of bowel out of the way, giving the ultrasound transducer a clear acoustic window. Without that fluid-filled cushion, the image can be grainy or incomplete.
The standard instruction is to drink 28 to 32 ounces of clear fluid (water is ideal) and finish it one hour before your scheduled appointment time. That gives your kidneys enough time to filter the liquid into your bladder. Don’t empty your bladder until the sonographer tells you the scan is done. Yes, it will feel uncomfortable, especially with a transducer pressing on your lower abdomen. Most people find it manageable for the 20 or so minutes the scan takes.
When You Don’t Need a Full Bladder
After about 16 weeks, the uterus has grown large enough to rise above the pelvic brim on its own, so a full bladder no longer improves the image. For the 20-week anatomy scan and any later ultrasounds, most facilities will ask you to come with an empty bladder. In fact, an overfull bladder later in pregnancy can actually distort the image, making structures like the cervix or the placenta’s position harder to read accurately.
If your provider orders a transvaginal scan at any point, you should empty your bladder right before the procedure. The probe sits much closer to the uterus during a transvaginal exam, so a full bladder just gets in the way. Sometimes a first-trimester appointment involves both a transabdominal and transvaginal scan. In that case, you’ll start with a full bladder for the abdominal portion, then be asked to use the restroom before the transvaginal part.
Eating and Drinking Before the Scan
A standard pregnancy ultrasound does not require fasting. You can eat a normal meal beforehand. There are no restrictions on caffeine or specific foods. The only dietary instruction that matters is the water intake for early scans described above. If your appointment also involves blood work (some combined screening tests pair an ultrasound with a blood draw), your provider’s office will tell you separately whether fasting is needed for that portion.
Skip Lotions and Creams on Your Skin
On the day of the scan, avoid applying lotions, oils, or creams to your abdomen. These products can interfere with the transducer’s contact and reduce image quality. The sonographer will apply their own water-based gel, which conducts sound waves effectively. If you’ve already put on lotion, it’s not a disaster, but wiping the area clean before the scan helps.
What to Wear
A separate top and bottom is the easiest choice. The sonographer needs access to your bare abdomen from just below the bra line to your hip bones, so you’ll pull your top up and tuck a towel into the waistband of your pants or skirt to protect them from the gel. Most patients don’t need to change into a hospital gown for a prenatal ultrasound. A dress works too, though you’ll need to pull it up higher than you might expect. Jewelry and a watch are fine.
Comfort matters more than you might think. The anatomy scan at 20 weeks can take up to 45 minutes if the baby is in a tricky position, and you’ll be lying on your back or slightly reclined for the duration. Stretchy, loose-fitting clothes make that much more pleasant. Later in pregnancy, some women feel lightheaded lying flat, so the table is usually angled to keep your head elevated.
What to Bring
Your provider’s office will typically tell you exactly what paperwork they need, but a short checklist covers most situations:
- Photo ID and insurance card. Even if the office already has your information on file, many imaging departments verify both at check-in.
- Referral or order form. If your OB or midwife referred you to a separate imaging center, bring the written order or confirm it was sent electronically.
- Your last menstrual period date or estimated due date. The sonographer uses this to determine which measurements to prioritize and whether fetal size is tracking as expected.
- A list of questions. If you want to ask about the baby’s position, placenta location, or gender, write it down. It’s easy to forget in the moment.
What Happens During the Appointment
A routine pregnancy ultrasound takes about 20 minutes. The 20-week anatomy scan is longer, typically 30 to 45 minutes, because the sonographer is systematically checking the brain, spine, heart chambers, kidneys, limbs, and placenta. You’ll lie in a semi-reclined position while the sonographer moves the transducer across your abdomen with steady pressure. The gel feels cool at first but warms quickly.
The sonographer may be quiet during parts of the exam while they concentrate on capturing specific measurements. This is normal and doesn’t mean something is wrong. In many practices, a radiologist or maternal-fetal medicine specialist reviews the images after the scan, so your sonographer may not be able to discuss findings in detail on the spot. Your provider will follow up with results, usually within a few days.
If you’re having a transvaginal scan, you’ll be asked to undress from the waist down and position yourself with your feet in stirrups or on the edge of the table. The probe is slim, covered with a disposable sheath and lubricant, and most people describe it as mildly uncomfortable rather than painful. These scans are shorter, often 10 to 15 minutes.
Quick Reference by Trimester
- Before 14 to 16 weeks: Drink 28 to 32 ounces of water, finishing one hour before the appointment. Keep your bladder full until the scan is complete.
- 16 weeks and beyond: No full bladder needed. Arrive with a comfortably empty bladder.
- Transvaginal scan (any stage): Empty your bladder immediately before the procedure.
- All scans: Eat normally, skip abdominal lotions, wear a separate top and bottom, and bring your ID and insurance card.