O29.011 Aspiration pneumonitis due to anesthesia during pregnancy, first trimester

ICD-10-CM Code O29.011: Aspiration pneumonitis due to anesthesia during pregnancy, first trimester

ICD-10-CM code O29.011 represents aspiration pneumonitis due to anesthesia during pregnancy, first trimester, classified as a pathologic function. Aspiration of gastric contents during obstetric anesthesia can cause a chemical lung injury that may progress to acute respiratory distress syndrome. Terminology sources list distinct codes for other pregnancy trimesters, and clinical literature describes physiological changes of pregnancy that amplify aspiration risk. 1 3 5

Plain-language overview

Code O29.011 identifies aspiration pneumonitis due to anesthesia during pregnancy, first trimester, and the concept is categorized as a pathologic function. Aspiration of stomach contents into the lungs during obstetric anesthesia can precipitate a chemical pneumonitis that progresses to acute respiratory distress syndrome within hours. 1 5

What this code represents

The official display label for O29.011 is aspiration pneumonitis due to anesthesia during pregnancy, first trimester. Terminology sources list this diagnosis alongside separate codes for aspiration pneumonitis due to anesthesia during pregnancy in the second trimester, third trimester, and unspecified trimester. 3 4

Clinical context

Pregnancy amplifies the risk of aspiration because most women have a gastric pH below 2.5, and about 60 percent harbor gastric volumes over 25 mL. Placental gastrin increases acid secretion, while the enlarging uterus and progesterone-mediated smooth muscle relaxation lower esophageal sphincter tone and delay gastric emptying. 1

Airway anatomical changes in pregnant women make intubation more difficult, increasing the risk of aspiration during general anesthesia. Volumes of gastric contents as small as 0.3 mL/kg with a pH below 2.5 can damage the alveolar epithelium, and food particles exacerbate injury even at higher pH. 1

Coverage and utilization context

Pulmonary aspiration is one of the most important complications of obstetric anesthesia. Measures to reduce this risk include preoperative fasting, non-particulate antacids, H2 receptor blockers, gastro kinetic drugs like metoclopramide, rapid sequence induction with cricoid pressure, and awake extubation during emergence from general anesthesia. 2

What the sources add

Clinical literature describes aspiration pneumonitis as a sterile chemical injury distinct from aspiration pneumonia, noting that no guideline currently addresses this distinction. Terminology sources provide the code hierarchy and display labels for aspiration pneumonitis due to anesthesia during pregnancy across different trimesters. 1 3

Documentation considerations

Terminology sources list distinct codes for aspiration pneumonitis due to anesthesia during pregnancy for the first, second, third, and unspecified trimesters. The supplied excerpts do not state a coding rule that clinical documentation must specify the pregnancy trimester to select the correct code. 3 4

Questions to verify

Clinical literature references retrospective series involving cesarean deliveries under general anesthesia and physiological changes of pregnancy. The supplied excerpts do not establish whether these specific incidence figures and risk factors apply identically to the first trimester. 1 3

Sources

1. Short-term corticosteroid therapy in aspiration pneumonitis complicated by acute respiratory distress syndrome: A case report — pmc.ncbi.nlm.nih.gov; accessed 2026-07-25.
2. The current practice of aspiration prophylaxis in obstetric anesthesia: a survey among non-physician anesthetic providers working in hospitals in Ethiopia — pmc.ncbi.nlm.nih.gov; accessed 2026-07-25.
3. Phecode 646 · ExPRSweb — csg.sph.umich.edu; accessed 2026-07-25.
4. EVS Explore — evsexplore.semantics.cancer.gov; accessed 2026-07-25.
5. EVS Explore — evsexplore.semantics.cancer.gov; accessed 2026-07-25.