Nobody really knows why some pregnant women cringe at the sight of meat or heave at the smell of coffee, although there are some theories. Many women experience a heightened sense of smell while pregnant, which may account for some food aversions. Some scents — like garlic, for instance — can be too potent to seem palatable. Because progesterone slows down the digestive tract, which may lead to constipation and indigestion, pregnant women may also instinctively stay away from meats and gassy veggies like broccoli that can be hard to digest, says Dr. Gil Gross, an associate professor of obstetrics and gynecology at Washington University in St. Louis.