Brown discharge off and on during the 30th week of pregnancy may be due to preterm labor, placenta praevia, gynecological inflammation and other reasons. 1. Preterm labor: At 30 weeks of pregnancy, if a woman experiences contractions and abdominal pain, especially when accompanied by brown vaginal discharge, it suggests the possibility of preterm labor. 2. Placenta praevia: after 28 weeks, the placenta position is located in the lower part of the uterus and covers or reaches the endocervical os, considering the presence of placenta praevia, painless vaginal bleeding will occur during pregnancy, which can be manifested as brown vaginal discharge, and can be clearly diagnosed by ultrasound. 3. Gynecological diseases. Women with gynecological diseases such as cervicitis and cervical polyps are prone to abnormal leukorrhea. Brown discharge may appear after intercourse during pregnancy. If the pregnant woman in the 30th week of pregnancy intermittent brown discharge, belong to the abnormal situation, it is recommended to consult a doctor in time, under the guidance of the doctor, improve the relevant examination, clarify the cause of the disease, symptomatic treatment.