Write SQL query to solve given problem: How many mothers have taken immunization during prenatal visit?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(DISTINCT T2.PATIENT) FROM encounters AS T1 INNER JOIN immunizations AS T2 ON T1.PATIENT = T2.PATIENT WHERE T1.REASONDESCRIPTION = 'Normal pregnancy' AND T1.DATE = T2.DATE