(My real “Week Forty” pregnancy post is coming later. This is just an informational post about due dates for those who are interested.)
As many of you know, I went past 40 weeks with Vera. Thirteen days past, actually. Many of us rely on that “magical due date” to predict when our little sweetie will arrive, but the system for calculating it is actually rather flawed. First of all, this method (which dates back to the 1700’s) assumes that each woman’s cycle is the same length (28 days). A woman with shorter cycles is going to have a shorter gestation, and likewise, a woman with longer cycles will have a longer gestation. Secondly, this method incorrectly represents a lunar month as 280 days rather than the actual 295 days (yep… a 15 day difference!).(1)
A more accurate method for determining one’s due date (Mittendorf, et. al. 1990 study) is to take the date of your last cycle, subtract 3 months, and add 15 days (for first time moms) or 10 days (for moms who have previously given birth).(2) According to this way of calculating, I am not actually even “due” until February 18 or 19.
Another source suggested taking the doctor’s calculated due date for you (280 days) and adding or subtracting days based on the average length of your cycle. Add or subtract 2 days for every day difference there is between your cycle length and the standard 28 days. If you typically have a cycle that lasts 30 days, add 4 days to the end of your “due date” (from the doctor), and if you normally have a shorter cycle (like 27 days), subtract 2 days.(3) According to this way of figuring the due date, I am due February 19 or 20.
I also found some really interesting information about inductions. You may have heard that it is important to be induced at 41 weeks (I was told last time by my doctor that after 41 weeks the risk of stillbirth doubles), yet did you know that the American College of Obstetricians and Gynecologists (ACOG) does not recommend labor induction until 42 weeks? In a study done of over 56,000 pregnancies, the ACOG concluded: “Routine labor induction at 41 weeks likely increases labor complications and operative delivery without significantly improving neonatal outcomes.”(4) Interesting! I’ll definitely be pushing for a late induction date (right at 42 weeks, if possible) if I am still pregnant at that point.
I hope that this post has been informative for you. I feel like I’m learning a lot right now… not just about pregnancy/delivery, but about patience and trusting in God for HIS perfect timing!
When our family went through a difficult time when I was in middle school, we clung to this verse: “Some trust in chariots and some in horses, but we trust in the name of the LORD our God” (Psalm 20:7). We filled in “chariots” and “horses” with what we were tempted to trust in at the time, and determined to trust in GOD, not in those things! Some may trust in doctors and due dates, but we trust in the name of the LORD our God! 🙂
Sources:
(1) The Lie of the EDD
(2) Ibid.
(3) gentlebirth.org
(4) Forty Weeks and Beyond
