Obviously she could not procreate with anyone else besides Ron... But she was adamant that that would never happen. She became more erratic and finally snapped to one night disappear for hours before coming back. In her arms had been an infant. Draco had been shocked when he realised she had stolen a baby away in the night. He had tried to convince her that she had to return the child, she eventually agreed after three days. But a month later she one night just got up and demanded he go with her, they returned that night with another baby. Draco did not say anything then, she already knew what he would say. And thus began this trend, every month for the last six months, she would steal a baby and keep them for three days before returning them. He would always accompany her, they did everything together and he would never not support her. He just made sure they were put back on the third night every time.