When a condition like asthma occurs during pregnancy, it is medically defined as a complicating factor. This means the condition can influence or be influenced by the pregnancy, requiring specific management and monitoring. To categorize and report these instances for healthcare data, billing, and statistical purposes, medical professionals use the International Classification of Diseases, 10th Revision (ICD-10).
Clinical Impact of Asthma During Pregnancy
The physiological changes of pregnancy can affect a woman’s asthma. For about one-third of pregnant women with asthma, their symptoms worsen, while another third may see improvement, and the remainder experience no significant change. Uncontrolled asthma presents risks, as the primary concern is maintaining adequate oxygen supply for both the mother and the developing fetus.
Poorly controlled asthma can increase the mother’s risk for developing preeclampsia, a disorder characterized by high blood pressure, and other hypertensive disorders during pregnancy. For the fetus, poorly managed maternal asthma is linked to adverse outcomes. These include a higher likelihood of preterm birth (delivery before 37 weeks of gestation), low birth weight, and intrauterine growth restriction, where the baby does not grow at a normal rate.
Primary ICD-10 Coding for Asthma in Pregnancy
To accurately report asthma that complicates a pregnancy, medical coders use a specific category within ICD-10. The primary codes are in the block O99.5-, designated for diseases of the respiratory system that complicate pregnancy, childbirth, and the period after delivery. These codes are for the maternal health record and establish a direct link between the respiratory illness and the obstetric experience.
This category is broken down into three subcategories that reflect the timing of the complication. The code O99.51 is used when a respiratory condition like asthma complicates the pregnancy itself. This is the code applied during routine prenatal visits for issues arising before labor begins.
When the respiratory condition affects labor and delivery, the code O99.52 is assigned. Following delivery, if asthma continues as a complicating factor during the postpartum period, coders use O99.53. The puerperium is the six-week period immediately following childbirth.
Applying Specificity with Additional Codes
The O99.5- codes are not intended to be used alone, as they only indicate a respiratory condition is complicating pregnancy without specifying the condition itself. To provide a complete clinical picture, a second code is required from the J45 category, which classifies asthma by its type and severity. This dual-coding system ensures that health records capture both the obstetric context and the specific nature of the patient’s respiratory disease.
For instance, after the primary code O99.51, a coder would add a code such as:
- J45.2- for mild intermittent asthma
- J45.3- for mild persistent asthma
- J45.4- for moderate persistent asthma
- J45.5- for severe persistent asthma
Each of these asthma codes can be further specified to indicate if the patient is experiencing an acute exacerbation or has status asthmaticus.
The O99.51 code also requires a final character to denote the trimester of the pregnancy. A “1” is added for the first trimester (e.g., O99.511), a “2” for the second trimester (e.g., O99.512), and a “3” for the third trimester (e.g., O99.513).
Essential Documentation for Accurate Coding
For medical coders to assign the correct ICD-10 codes, the physician’s documentation must be specific. The record must contain a definitive diagnosis of asthma and explicitly state that the condition is complicating the pregnancy. Without this direct link established by the provider, the O99.5- code category is not appropriate.
The documentation must also specify the severity and status of the asthma. Details such as “mild persistent asthma” are necessary to select the correct code from the J45 category. The current trimester must also be clearly noted in the record for the assignment of the correct final character for the O99.51- code.
Official coding guidelines mandate that the code from the O99.5- category be sequenced first. This is followed by the specific asthma code from the J45 category to ensure a standardized claim.