A recent study has thrown the 9-month pregnancy estimate out the window, showing that durations can vary by up to 5 weeks.
If you’ve been under the impression that pregnancies last 9 months you’re not alone. A recent study has thrown that estimate out the window, though, showing that durations can vary by up to 5 weeks.
Their research was begun in the mid-80s, during which time they followed 125 single-birth pregnancies, all of which had been conceived naturally.
They asked the mothers give a urine sample daily and used them to calculate the exact day of conception.
Years later, they contacted the moms to find out what their delivery dates were.
The average gestation was just over 38 weeks, but women reported variances of up to 37 days.
Further research revealed that factors contributing to the large differences include age, the mother’s own birth weight, and hormones.
Older moms tended to be pregnant longer. For each year of age about a day was added to the duration.
Women who were heavier when they were born experienced a longer pregnancy of about one day for every 3 and a half ounces of birth weight.
Finally, late rises in progesterone levels resulted in shorter pregnancies by up to 12 days.