Which CPT codes are appropriate for a first‑trimester viability ultrasound (transabdominal vs transvaginal) and what ICD‑10‑CM diagnosis code should be used?

Diagnostic Coding for First-Trimester Viability Ultrasound

For a first-trimester viability ultrasound, use CPT code 76801 (first trimester transabdominal) or 76817 (transvaginal) depending on the approach performed, paired with ICD-10-CM diagnosis code Z36 (encounter for antenatal screening) or O26.841 (supervision of pregnancy with history of in vitro fertilization) if applicable to the clinical scenario.

CPT Code Selection

Transvaginal Approach (Preferred)

• CPT 76817 is the appropriate code for transvaginal ultrasound in the first trimester, as transvaginal ultrasound is the preferred and most appropriate imaging modality for early pregnancy evaluation according to the American College of Radiology 1
• Transvaginal ultrasound provides superior resolution for evaluating early pregnancy structures, the endometrium, and adnexa compared to transabdominal scanning 2, 3

Transabdominal Approach

• CPT 76801 is used for transabdominal ultrasound of a pregnant uterus in the first trimester (real-time with image documentation), fetal and maternal evaluation 1
• Transabdominal ultrasound is often complementary to transvaginal ultrasound and may sometimes be adequate alone, particularly later in the first trimester 1

Combined Approach

• When both transabdominal and transvaginal ultrasound are performed (which is often clinically appropriate), both CPT codes may be billed if documentation supports the medical necessity of each approach 2
• A combined approach allows comprehensive evaluation of structures that may be positioned too high for transvaginal visualization alone 2

ICD-10-CM Diagnosis Code Selection

Primary Screening Code

• Z36 (Encounter for antenatal screening of mother) is the most straightforward diagnosis code for a routine viability scan 1

Clinical Context-Specific Codes

• O26.841 - Pregnancy with history of in vitro fertilization (if applicable)
• O09.00 - Supervision of pregnancy with history of infertility, unspecified trimester
• O26.851 - Spotting complicating pregnancy, first trimester (if bleeding is present) 1, 4
• O20.0 - Threatened abortion (if viable pregnancy with bleeding and closed cervix) 5
• O02.1 - Missed abortion (if non-viable pregnancy is diagnosed) 1
• O00.9 - Ectopic pregnancy, unspecified (if ectopic pregnancy is suspected or diagnosed) 1, 4

Clinical Documentation Requirements

Essential Elements for Coding Support

• Document the specific indication for the ultrasound (routine viability assessment, vaginal bleeding, pain, history of pregnancy loss, etc.) 1
• Record whether transabdominal, transvaginal, or both approaches were used and the clinical rationale for each 1, 2
• Include findings regarding gestational sac presence and location, embryonic cardiac activity, crown-rump length, yolk sac visualization, and adnexal structures 2, 6

Key Viability Parameters to Document

• Presence or absence of intrauterine gestational sac 6, 7
• Embryonic cardiac activity (documented with M-mode or video clips, not Doppler in normal pregnancies) 4
• Crown-rump length measurement for dating 2, 5
• Yolk sac appearance 2, 3
• Mean sac diameter if embryo not yet visible 8

Common Coding Pitfalls

Avoid These Errors

• Do not use second or third trimester ultrasound codes (76805,76811,76815) for first-trimester examinations 1
• Do not bill for Doppler studies (76820) when evaluating a normal or potentially normal intrauterine pregnancy in the first trimester due to concerns about bioeffects on the developing embryo 4
• Ensure the gestational age documented supports first-trimester coding (up to 13 weeks 6 days from last menstrual period) 1
• Do not use CPT 76856 (non-obstetric pelvic ultrasound) for pregnancy evaluation, even in very early gestation 1

Documentation Must Support Medical Necessity

• The clinical indication must justify the specific approach used (transvaginal vs transabdominal) 1, 2
• If both approaches are performed, document why each was medically necessary (e.g., transabdominal for overview, transvaginal for detailed evaluation of early structures) 2