Doctors use due dates as a way to ensure that necessary prenatal care is given at the right stages of pregnancy and to measure the baby’s growth. Baby due dates are generally calculated to be 40 weeks after the start of the pregnant woman's last menstrual cycle, based on the assumption that an average cycle lasts for 28 days. But since many women have cycles that differ from the standard 28 days, baby due dates don’t tend to be entirely accurate; it is estimated that just 4% of women give birth on their actual due dates. However, about 60% of women do give birth within a week of their predicted due dates.
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