Nah, those women are probably also using formula. It's really hard for a woman to get pregnant while breastfeeding. And breastfeeding till two is normal and healthy. That would make each child around 3 years apart. Plenty of time. Ancient people didn't have firtility apps. You don't need it. That's how nature intended. People should not fight nature. But work within it. This is the way, the 道。