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I have heard mentioned here that the average time for a first time mother is 41 weeks and 2 days. I assume that births distribute in a bell-curve shape, and 41+2 is the peak. Does anyone have any links to info about that bell curve? I would like to know what a standard deviation is for that curve.<br><br>
Basically, if I am due Aug 8 based on LMP, I figure I should consider Aug 17 to be more likely. I would like to calculate the chance of giving birth ON Aug 8, and the chance of giving birth before July 28. I am considering signing up for a class on July 28, and would like to know if that is a bad idea.<br><br>
So, if there is a site somewhere that has statistical data for pregnancy and birth, I would love to take a look.

#### chandasz

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Wow mamma! You are looking for such a scientific guarantee and there are none! There is a Harvard study that shows that average gestation for a first time mom is 41 1/7 weeks. Yes, average is that line that goes down the middle of the bell curve meaning that most people go longer or shorter....<br><br>
The bell curve is a mathematical concept that I'm sure you can google.<br><br>
Go ahead and sign up for your class if you won't die if you miss it!LOL<br><br>
Find out how long your mom carried as that can be a predictor.... but again- not a guarantee.<br><br>
Your baby will be born when your baby is ready and you will NOT know when that will be until they arrive. LOL<br><br>
Relax. Enjoy your pregnancy!

#### jessitron

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Putting everything on hold just in case the baby comes early will make you even more itchy for the baby to come. Come end of July, you won't need any extra desire for the baby to arrive.

#### Xiao

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Hi,<br><br>
I had looked for this also, but did not find it. I searched the internet, and the university databases on medical research and got nothing. Frustrating!<br><br>
I did find a few things on primips and signs of post-maturity in the baby (see the references cited in this link: <a href="http://www.gentlebirth.org/archives/datesppr.html#POSTMATURITY);" target="_blank">http://www.gentlebirth.org/archives/...POSTMATURITY);</a> but nothing specific for that Harvard study that has something on average gestation length for first time moms (everyone seems to refer to this without citing it specifically...). Without looking at the specifics, you don't even know if the curve is bell shaped. It could be skewed to the left or right, flattened, or differ in some other way from the standard normal curve. Also it would be good to know more about the characteristics of the women who were included in the sample.<br><br>
I had my first baby a month ago, he decided to come out 8 days past his estimated arrival date. Reportedly I was about a week late myself, but I was the second baby, not the first.<br><br>
If you sign up and explain your circumstances could you possibly get your money back if it turns out you can't attend?<br><br>
Good luck!

#### engineer_mom

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considering a large number of births are induced, were they incorporated in the study?<br><br>
i remember reading a journal article awhile ago, but did not remember seeing a bell curve.

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<div style="margin:20px;margin-top:5px;">
<div class="smallfont" style="margin-bottom:2px;">Quote:</div>
<table border="0" cellpadding="6" cellspacing="0" width="99%"><tr><td class="alt2" style="border:1px inset;">
<div>Originally Posted by <strong>chandasz</strong> <a href="/community/forum/post/7939157"><img alt="View Post" class="inlineimg" src="/community/img/forum/go_quote.gif" style="border:0px solid;"></a></div>
<div style="font-style:italic;">Wow mamma! You are looking for such a scientific guarantee and there are none! There is a Harvard study that shows that average gestation for a first time mom is 41 1/7 weeks. Yes, average is that line that goes down the middle of the bell curve meaning that most people go longer or shorter....<br><br>
The bell curve is a mathematical concept that I'm sure you can google.<br><br>
Go ahead and sign up for your class if you won't die if you miss it!LOL<br><br>
Find out how long your mom carried as that can be a predictor.... but again- not a guarantee.<br><br>
Your baby will be born when your baby is ready and you will NOT know when that will be until they arrive. LOL<br><br>
Relax. Enjoy your pregnancy!</div>
</td>
</tr></table></div>
I know there is no guarantee. I was just curious from a statistical analysis point of view.<br><br>
I know I can find examples of a normal bell curve, but I want to see the bell curve for THIS data, or at least the technical data about this particular data. I don't need to SEE the curve itself. Data about it, like the standard deviation, would be very helpful.<br><br>
My mom was right on schedule (40 weeks give or take a day or 2) with both of us.<br><br>
I know there is no guarantee.<br><br>
BTW, I guess I didn't give enough info. It is not a matter of taking the class or not taking the class. I can take the class a week earlier, a month earlier, etc. But, someone I know will be taking it on that day and I would like to have the class together if we can.<br><br>
My feeling is that it is unlikely for me to give birth 20 days before the 41+2 point, but I am curious about how statistically unlikely. 10%, 5%, 1%. I understand that even if the chance is 1%, I could be that 1%.<br><br>
My personal feeling is Aug 20. My MW still thinks Aug 8.

#### tanya1976

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Seriously consider that your baby can come two weeks ahead as well. You get two weeks before or after. I wouldn't chance it. It seems too close.

#### lyttlewon

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<div style="margin:20px;margin-top:5px;">
<div class="smallfont" style="margin-bottom:2px;">Quote:</div>
<table border="0" cellpadding="6" cellspacing="0" width="99%"><tr><td class="alt2" style="border:1px inset;">
<div>Originally Posted by <strong>Lady Lilya</strong> <a href="/community/forum/post/7939097"><img alt="View Post" class="inlineimg" src="/community/img/forum/go_quote.gif" style="border:0px solid;"></a></div>
<div style="font-style:italic;">I have heard mentioned here that the average time for a first time mother is 41 weeks and 2 days. I assume that births distribute in a bell-curve shape, and 41+2 is the peak. Does anyone have any links to info about that bell curve? I would like to know what a standard deviation is for that curve.<br><br>
Basically, if I am due Aug 8 based on LMP, I figure I should consider Aug 17 to be more likely. I would like to calculate the chance of giving birth ON Aug 8, and the chance of giving birth before July 28. I am considering signing up for a class on July 28, and would like to know if that is a bad idea.<br><br>
So, if there is a site somewhere that has statistical data for pregnancy and birth, I would love to take a look.</div>
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</tr></table></div>
Actually it wouldn't be a bell curve (normal distribution) because you would have limited data, i.e. start at 0 and end at 40 something. You would have a tail at one end and a mode would do you more good than an average so standard deviation wouldn't mean as much. I know what you are looking for but I have never seen it.

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