How many babies can fit inside one woman?

The short answer:

How do so many babies fit in one woman? The limit isn't so much the number of babies as their volume and weight. In general, once the total weight of the babies inside reaches about 12 pounds, the uterus goes into labor. The greater the number of fetuses, the earlier the labor will occur. (The rough formula for due dates is to start at 40 weeks of gestation for one baby and subtract three weeks for each additional child: 37 for twins, 34 for triplets, etc. It's remarkable, then, that eight fetuses were able to gestate for 30 weeks, as in the California case.) Labor can also occur if a sac ruptures and introduces bacteria into the uterus or if one of the fetuses isn't growing correctly and signals the uterus to induce labor.