盆腔内 meaning in English

in pelvis
intrapelvic

Should be yesterday was pregnant 46 days , went to a hospital doing b to exceed check , but the doctor says to did not discover what thing , discover inside pelvic cavity namely " black hole " , say a possibility too do not look down upon , how to meet such
昨天应该算是怀孕46天了吧，去医院做了b超复查，可是医生说没发现什么东西，就是在盆腔内发现一个“黑洞” ，说可能太小看不到，怎么会这样呢？