First, how do we come up with a due date? There are several methods for determining the likely timeframe of delivery, including the gestation calculator wheel, Naegele's rule, lunar reckoning, Wood's method, Mittendorf's study, and ultrasound.
Naegele's Rule is probably the most common formula. It is calculated by:
Date of Last Menstrual Period + 7 days – 3 months = EDB
Naegele's rule assumes a 28-day menstrual cycle with ovulation around day 14, so it does not account for individual cycle variations from woman to woman. If a woman is fairly certain of the conception date, she can use an adjusted version of Naegle's rule:
Date of conception + 7 days – 3 months = EDB
The majority of women deliver within 10-14 days on either side of their due date, but only about 5% deliver on that exact date.
However, there are some other factors that should also be considered in determining a due date, including:
- Family gestation history
- Average menstrual cycle length
- Cycle regularity
- Characteristics of the last two periods
- Date she thinks she conceived
- When fetal movement was felt
- When heart tones could be heard
If you factor in the above questions, you may conclude that there is a more holistic way of guessing when to expect a baby than the pregnancy wheel they pull out in the OB's office at every appointment. For example, a woman who regularly has 35-day menstrual cycles likely ovulates a week later than the woman with a 28-day cycle. At the end of pregnancy, this may mean induction for being post-dates, which can lead to unnecessary cesareans (and even premature babies).
However you calculate it, and no matter how well acquainted you are with the statistics, it is HARD to wait for a baby, especially after you reach the estimated date of delivery. It's hard for Amie and me with our own babies, and it's hard when we wait for our friends and families (we try so hard not to be those people who call every day to ask if you're still pregnant).
I recommend that my clients start planning something fun every day when they get to the end of their pregnancies. Having something to look forward to can help maintain your sanity when you really hoped labor would have begun by now! Some ideas:
- Go to a movie
- Eat at a nice restaurant. You will miss tablecloths in the coming years.
- Get a pedicure or massage
- Make your postpartum pads
- Spend romantic time with your partner
- Work on a project around the house