In simple words: This code is used when a woman already has high blood pressure before becoming pregnant, and this high blood pressure causes problems during her pregnancy, delivery, or the period after delivery.

This code classifies pre-existing essential hypertension that complicates pregnancy, childbirth, or the puerperium.It includes cases of pre-existing hypertension with pre-existing proteinuria complicating these periods.It excludes pre-existing hypertension with superimposed pre-eclampsia.

Example 1: A 35-year-old woman with a history of hypertension presents for her first prenatal visit at 8 weeks gestation.Her blood pressure is elevated, and she is diagnosed with O10., A 28-year-old woman with pre-existing hypertension experiences worsening hypertension and proteinuria during her 24th week of pregnancy.She is diagnosed with O10 and receives treatment to manage her blood pressure., A 40-year-old woman with a history of hypertension develops severe hypertension postpartum. This is coded as O10 and requires close monitoring and management.

Detailed history of hypertension, including onset, duration, and prior treatment.Documentation of blood pressure readings throughout pregnancy and postpartum period.Laboratory results (e.g., urinalysis for proteinuria).Treatment plan and response to treatment.

** Always ensure proper documentation to support the diagnosis.The code should only be used for maternal records, never for newborn records.Differential diagnosis should rule out other hypertensive conditions such as superimposed pre-eclampsia (O11).