My partner’s biggest fear is twins, or “double babies,” as we’ve affectionately dubbed them. I wanted to know why assisted hatching can sometimes result in twins. Assisted hatching helps the blastocyst hatch out of the zona pellucida before it can implant. This helps in certain cases, for example, if the zona is hard or thick. Scientists are still trying to understand how assisted hatching can lead to twins. One idea proposed: the blastocyst’s inner cell mass gets stuck in a figure 8 and divides into identical twins.