Since I chart and practice FAM (fertility awareness method) I always know when I ovulate. Always. Even if I weren’t charting, I would know. After years of paying attention to the signs of my fertility I cannot not know what is going on. Because of this, when I get pregnant I always know how to date a pregnancy and what my true EDD (estimated due date) is. When I go in for an ultrasound and the baby isn’t measuring up to my dates I know something is very wrong. For my most recent pregnancy, when I went in for an ultrasound and their measurements were spot on to mine I knew all was well.
Pregnancy dating is based on the assumption that every woman has a 28 day cycle and that ovulation occurs on day 14. Care providers assume that women ovulate 2 weeks after the first day of their last period, and get their periods 2 weeks after they ovulate (the period of time from ovulation to when you get your period is called the luteal phase). Yes, some women have these regular text book cycles, but a lot of women do not. I am one of those women who absolutely, positively does not have a regular cycle. My cycles even differ from each other, month to month.
To calculate a due date you simply add 38 weeks to the date you ovulated/conceived and that is your estimated due date.
The date of conception/ovulation isn’t always the day you had sex. Sperm can live in your body for 5-6 days which could mean that the date of conception could be up to 6 days after you did the deed.
Because most care providers want a LMP (last menstrual period) date on the first appointment, instead of giving them my true LMP I subtract two weeks from my ovulation date so that everybody will calculate the same EDD as I did.
For example, my true LMP was 2/29/2012 (shhh don’t tell my doctors and midwives!) which would make my EDD 12/5/2012 which is wrong, wrong, wrong. My real due date is 12/13/2012. If I went by my true LMP date I would be more than a week off. For all those mamas who have their babies after their due dates we all know how valuable that extra week of time is in order to avoid an induction.
(Update: I gave birth to my daughter on 12/12/12 and I guarantee you if I had the estimated due date of 12/5/12 induction would have been a topic of conversation between my care provider and I! Because I used my TRUE estimated due date we never even talked about it. Information is empowering!)
Also, to know my true EDD and not have someone tell me also gives me a sense of control and empowerment. I like to inform doctors of my body, and not them inform me of it instead.
For all those
psycho planners out there like me the BabyMed Fertility and Pregnancy Calculator iPhone app is great. It shows a calendar and on each day it tells you how far along you are. It also tells you when your major milestones are. Best of all, it’s free!
The moral of this story is to educate yourself. Know your body, your cycles and give yourself the upper hand by knowing your EDD before you see your care provider. Also, if this article is hard to understand I recommend reading the book Taking Charge of Your Fertility so that you can understand what in the world I’m talking about. 🙂