O36.8339 Maternal care for abnormalities of the fetal heart rate or rhythm, third trimester, other fetus

ICD-10-CM O36.8339: Maternal care for fetal heart rate or rhythm abnormalities, third trimester, other fetus

ICD-10-CM code O36.8339 identifies maternal care for abnormalities of the fetal heart rate or rhythm during the third trimester for another fetus. Fetal rhythm abnormalities include irregular, fast, or slow heart rates, often detected via Doppler during routine obstetrical assessment. This code is an active terminology concept with a specific parent category. 1 2

Plain-language overview

Code O36.8339 represents maternal care provided when an obstetrical clinician detects an abnormal fetal heart rate or rhythm, which can be irregular, too fast, or too slow, during a routine pregnancy assessment. 1 2

What this code represents

The official label for O36.8339 is maternal care for abnormalities of the fetal heart rate or rhythm, third trimester, other fetus, and the terminology record maintains an active status. 1

Within the coding hierarchy, O36.8339 is a narrower concept under the parent code O36.833, which covers maternal care for fetal heart rate or rhythm abnormalities in the third trimester. 1

Coding details

The code O36.8339 is distinguished from related codes by specifying the third trimester and other fetus, whereas separate codes exist for different trimesters and specific fetus numbers like fetus one or fetus two. 5

The semantic type assigned to the O36.8339 terminology concept is Pathologic Function, and a published abbreviation exists for the full official code description. 1

Documentation considerations

Clinical documentation for fetal rhythm abnormalities often involves evaluation techniques like M-mode or Doppler echocardiography to assess the mechanical atrial and ventricular relationship and identify specific arrhythmias. 2

Clinical context

Fetal rhythm abnormalities occur in up to two percent of pregnancies and account for ten to twenty percent of referrals to fetal cardiologists, though less than ten percent have sustained clinically significant tachyarrhythmia or bradyarrhythmia. 2

What the sources add

While the terminology record defines the code structure and active status, the clinical literature provides operational context by explaining that fetal signal acquisition limitations between 28 and 34 weeks make electrocardiography assessment impractical for most arrhythmias. 1 2

Multiple distinct sources, including terminology records and prenatal ultrasound documentation appendices, uniformly list O36.8339 with the identical official description for maternal care for fetal heart rate or rhythm abnormalities. 1 3 4

Sources

1. ICD-10-CM O36.8339 terminology record — National Cancer Institute Enterprise Vocabulary Services; accessed 2026-07-27.
2. Rhythm abnormalities of the fetus — pmc.ncbi.nlm.nih.gov; accessed 2026-07-27.
3. EVS Explore — evsexplore.semantics.cancer.gov; accessed 2026-07-27.
4. Prenatal Obstetrical Ultrasound Appendix B — hpo-docs.jh.edu; accessed 2026-07-27.
5. ICD-10-CM 2024 | O36 - Maternal care for other fetal problems — unboundmedicine.com; accessed 2026-07-27.