Hi~
Just wanted to share this info with anyone whose caregiver is telling her that her baby is “overdue” and pressuring her to get an induction/c-section to start her birthing. Of course, we all know that normal pregnancies can last 37-42 weeks but those pesky doctors can be persistent! (I call it my guess date or guess month as suggested by the Hypnobabies program.) ^^
In addition to asking for your Bishop’s score and ignoring sonogram interpretations that you have a “big baby,” you might use the following information to help support your decision to wait for your birth time to occur on its own.
The 40 week gestation model (280 days from the first day of last menses or 266 days from presumed ovulation) was put forth by Franz Naegele more than a hundred years ago. It is based on the idea that a woman’s menstrual cycle is 28 days and that gestation takes 10 cycles.
A study published in Obstetrics & Gynecology, in 1990, revealed that gestation time is not one-size-fits-all (surprise!). Factors such as age, race and whether or not a woman has birthed before can be used to factor her so-called due date.
In summary, the study found that median gestation time for 1st time mothers was 41 weeks and 1 day and 2nd/more time mothers was 40 weeks and 3 days.
I found this journal article referenced in my Hypnobabies homestudy workbook. You can purchase the full text of the study or find more quotes from it online. I have only read the abstract, which should be noted, only describes findings based on “private-care White mothers.” I don’t know if there are significant differences for various racial groups or for White moms using other types of care. Here is the article info:
The Length of Uncomplicated Human Gestation
MITTENDORF, ROBERT; WILLIAMS, MICHELLE A.; BERKEY, CATHERINE S.; COTTER, PAUL F. Obstetrics & Gynecology . 75(6):929-932, June 1990.
Abstract:
By retrospective exclusion of gestations with known obstetric complications, maternal diseases, or unreliable menstrual histories, we found that uncomplicated, spontaneous-labor pregnancy in private-care white mothers is longer than Naegele’s rule predicts. For primiparas, the median duration of gestation from assumed ovulation to delivery was 274 days, significantly longer than the predicted 266 days (P=.0003). For multiparas, the median duration of pregnancy was 269 days, also significantly longer than the prediction (P = .019). Moreover, the median length of pregnancy in primiparas proved to be significantly longer than that for multiparas (P=.0032). Thus, this study suggests that when estimating a due date for private-care white patients, one should count back 3 months from the first day of the last menses, then add 15 days for primiparas or 10 days for multiparas, instead of using the common algorithm for Naegele’s rule.