{
    "resourceType": "Patient",
    "id": "2",
    "maritalStatus": {
        "coding":  [
            {
                "system": "http://terminology.hl7.org/CodeSystem/v3-MaritalStatus",
                "code": "M"
            }
        ]
    }
}

<Patient xmlns="http://hl7.org/fhir">
    <id value="2" />
    <maritalStatus>
        <coding>
            <system value="http://terminology.hl7.org/CodeSystem/v3-MaritalStatus" />
            <code value="M" />
        </coding>
    </maritalStatus>
</Patient>