Manava Dharmashastra 5.66

5.66

rātribhir māsatulyābhir garbhasrāve viśudhyati
rajasy uparate sādhvī snānena strī rajasvalā //

(A woman) is purified on a miscarriage in as many (days and) nights as months (elapsed after conception), and a menstruating female becomes pure by bathing after the menstrual secretion has ceased (to flow).