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Overdue: A Great Resource for Mamas

I just posted a new blog entry on my Doula website that I wanted to share here, since this is someone many women birthing in a hospital will face. Here ya go!

Are you worried about going past the magical 40 weeks? It is actually very common for a woman to go past this mark, especially a first time mother. Why is this? Mainly because every woman's fertility cycle is different. When a woman's due date is calculated it is usually based off of U/S measurements (Which are notoriously unreliable) or off of your last menstrual period. Unfortunately using the LMP practitioners assume that the woman ovulated 14 days after the start of her period. This, unfortunately, is not the case for every woman as some ovulate on day 10, and some on day 20, and there are those with 40 days cycled who may ovulate on 35 days.

A further issue to cloud the fact of our 'due dates' is that 40 weeks was an average calculated by a doctor. He took a small sampling of women and based on their date of delivery found the 'average' to be at 40 weeks. Now if anyone knows anything about averages it is that in a wide sampling there are varieties of normal that go above or below the mark. This is true with pregnancy too. Plus when we reach 40 weeks, we have no actually completed our 40th week. We have completed our 39th week and still have 7 days to complete our 40th week. This means that if we're induced when we reach 39 weeks we are in essence only 38 weeks of being gestated.

Now why am I rambling on about all these lovely facts? Because there is a great website that I was just referred too by a friend who is a midwife. It is aimed at those wanting a home birth, but is useful for anyone wishing to educate themselves on 'post dates' pregnancy. Go check it out here: http://www.homebirth.org.uk/overdue.htm


( 1 comment — Leave a comment )
Aug. 15th, 2009 12:26 pm (UTC)
Just wanted to point out that early U/S are *not* notoriously unreliable. Early u/s are a good way of dating a pregnancy if a woman has irregular cycles, such as those who ovulate on day 10, 20, or 35. By early, I mean 8-10 weeks.

The website that you linked to also supports this, saying that "'If we look at how many women end up going 2 weeks over their due date, it is 9.5% according to dating by LMP but only 1.5% when dated by scan. This suggests that the dating of pregnancy by LMP tends to overestimate the gestation. Therefore if scan information is available, it is preferable to use this for dating a pregnancy (presuming it was carried out during the first half of pregnancy, when dating is most accurate).' [2]

Ultrasound scans for dating are pretty accurate in the first trimester, but get less and less accurate as time goes on. "

Later u/s (2nd and 3rd trimester) are, as you stated, unreliable in terms of dating.
( 1 comment — Leave a comment )

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