Home Media Article for health Pregnancy Ultrasound Schedule: How Often & When?

Pregnancy Ultrasound Schedule: How Often & When?

October 22 / 2026

Pregnant woman ultrasound

Ultrasound is an essential medical tool using high-frequency sound waves to assess development, screen for abnormalities, and closely monitor the health of the fetus. Ramkhamhaeng 2 Hospital is dedicated to helping expectant mothers feel confident throughout their pregnancy.

How many times do pregnant women need an ultrasound? When is the first ultrasound?

Mothers with a normal pregnancy generally undergo an ultrasound about 1–2 times (first and second trimesters). However, if there are high-risk conditions, a twin pregnancy, suspected fetal growth restriction or macrosomia, or complications, the doctor will schedule more frequent examinations as necessary.

First ultrasound: Can be done at 7–8 weeks (usually transvaginal) or at 12 weeks to confirm pregnancy, check heartbeat, check for multiple pregnancies, and accurately calculate the due date.

What is checked during each ultrasound? ?

1. First Trimester (5–14 weeks)

5–6 weeks: Check gestational sac, initial heartbeat, and diagnose/rule out ectopic pregnancy.
7–10 weeks: See the fetal body more clearly and observe the yolk sac (Yolk sac)
11–14 weeks: See head, torso, arms, legs, check nuchal translucency (NT), nasal bone, spine, abdominal wall, and assess preeclampsia risk.

2. Second Trimester (16–22 weeks - Anatomy Scan)

Detailed examination of organ completeness such as brain, 4-chamber heart, face and lips, spine, arms, legs, fingers, facial features, as well as determining sex, placenta position, and amniotic fluid volume.

3. Third Trimester (22–32 weeks and above)

Monitor growth, estimate weight, check fetal position, check blood circulation (Doppler ultrasound), amniotic fluid volume, and monitor potential late-term abnormalities.

What is the difference between 2, 3, 4D ultrasounds? Which one should I choose? ?

2 D: Black and white cross-sectional images, the main standard used by doctors to examine internal organs, assess body size, heart, brain, and fetal completeness.
3D: Processed from 2D images into a three-dimensional photograph-like image, showing external structures such as face, fingers, and bone structure more clearly.
4D (4D): Displays 3D images in real-time motion, showing fetal behavior such as smiling, yawning, or moving limbs.

Pregnant woman ultrasound

Which type to choose ?

For general health checks, 2D is sufficient and standard. If the doctor needs to look at specific lesions, 3D/4D is used in conjunction. For 4D to capture memorable keepsakes, it is recommended between 26–32 weeks when the fetus has accumulated fat and appropriate amniotic fluid.

Is frequent ultrasound dangerous? Does it affect the fetus in the womb ?

Ultrasound uses high-frequency sound waves reflected back to create images, without the use of radiation, so it is highly safe with no harmful side effects. However, medical guidelines recommend scanning only when indicated and under medical advice. Avoid scans solely for souvenir photography without necessity.

What to do if an ultrasound shows the baby's weight is below standard ?

If the fetus is found to be smaller than standard, the doctor will schedule close follow-up exams and may perform additional tests such as Doppler Ultrasound to measure blood flow, check amniotic fluid volume, placental function, or perform a Biophysical Profile (BPP) to plan care. The mother should eat nutritious food, get enough rest, and strictly attend appointments.

Preparation before ultrasound for the clearest images of your baby ?

Hydration and rest: Drink at least 2 liters of plain water daily for 1 week in advance (especially for 4D scans) to help maintain appropriate amniotic fluid levels for clearer images, and get 6–8 hours of adequate sleep.
Bladder preparation: For transabdominal scans in early pregnancy, the doctor may ask you to hold your urine to push the uterus up. However, if gestation is advanced or for a transvaginal scan, holding urine is unnecessary.
Clothing and timing: Wear comfortable clothing, easy to adjust, and allow about 30–45 minutes in case the baby turns away or covers its face with hands.

Pregnant woman ultrasound

FAQ: Frequently Asked Questions

Q1: Can ultrasound at 4 - 5 weeks detect anything ?

At 5 weeks gestation, you will start to see the gestational sac (Gestational sac) as a small black circle in the uterine cavity, but the fetus itself may not be visible yet, or fetal heartbeat can be detected.

Q2: What is seen at a 10-week ultrasound ?

During 7–10 weeks, the fetus grows to show a clear shape, and the yolk sac (Yolk sac) can be seen close to the fetus.

Q3: What is checked at 5 months / 20 weeks ultrasound ?

Around 18–20 weeks is the Anatomy Scan to thoroughly check all organs including brain, heart, heart valves, arms, legs, fingers, spine, abdominal organs, placenta position, amniotic fluid volume, and determine sex.

Q2: Can ultrasound results be wrong about the baby's gender? How likely is it ?

Discrepancies can occur if the fetus is in an improper position, such as crossing legs, blocking with hands, or if the mother has a thick abdominal wall, making it difficult for the doctor to clearly see the genitalia.

Ultrasound is a safe and effective technology to monitor growth and screen for fetal abnormalities. Understanding the purpose of each stage and proper preparation helps achieve the clearest results for the good health of the fetus.

References

Ramkhamhaeng Hospital. 4D Ultrasound Tracking Growth Throughout Pregnancy. Available from: https://www.ram-hosp.co.th/th/news_detail/639
Mayo Clinic. Fetal Ultrasound: Overview, Schedule, and Safety. Available from: https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/fetal-ultrasound/art-20546827
Cleveland Clinic. Ultrasound in Pregnancy: What to Expect, Schedule & Results. Available from: https://my.clevelandclinic.org/health/diagnostics/9704-ultrasound-in-pregnancy

For more information, please contact
Obstetrics and Gynecology Department 1st Floor, Ramkhamhaeng 2 Hospital
Email: information@ram2-hosp.com
Line Official: @ram2
Tel: 02-032-3888