How Many Ultrasounds Are Typical in the Third Trimester

Typical Number of Third-Trimester Ultrasounds

For most low-risk pregnancies, expect one or two ultrasounds in the third trimester, usually scheduled between 28 and 40 weeks. The count is not fixed; it depends on what your provider is monitoring and whether any complications develop.

Why a Third-Trimester Scan Is Done

Providers use late-pregnancy ultrasounds to check fetal growth, amniotic fluid levels, placental position, and baby's presentation. These scans help detect issues like intrauterine growth restriction, breech positioning, or low fluid that might change the delivery plan.

When More Than Two Scans Happen

Women with high-risk conditions — such as gestational diabetes, preeclampsia, multiples, or a history of preterm birth — may have additional ultrasounds. If a previous scan flagged a concern, your provider might order follow-up imaging every two to four weeks to track progress.

What Each Scan Measures

A typical third-trimester ultrasound evaluates the baby's estimated weight, head and abdominal circumference, femur length, and the position of the placenta. The cervix is not routinely measured on a standard growth scan unless there is a specific indication.

Ultrasound Type and Safety

Most third-trimester scans are transabdominal. A transvaginal approach is used only when the cervix needs a closer look, typically in cases of suspected preterm labor. Diagnostic ultrasound is considered safe when used for medical purposes, though guidelines recommend limiting scans to those with a clear clinical indication.

What If Your Provider Orders a Scan

A growth scan is often recommended between 32 and 36 weeks for routine monitoring, though timing varies. If your provider orders an additional ultrasound, ask what specific finding they are tracking and what the next step will be if the results are abnormal. Understanding the purpose helps you feel more prepared for each appointment.