Conception & Due Dates

IncognitoSuperhero

So we all know that our 40 week pregnancy due date is measured based on the first day of our last period, not the actual day you conceived. That is why it is 10 months, not 9 months. Because it includes the menstrual cycle, etc. Basically someone who conceived a few days or a few weeks after their period will have the same due date. (Period starts Oct 28, one can conceive Nov 7 or Nov 25 (or anywhere in between) and have same Aug 3 due date)

Does when you conceive affect when the baby arrives? For example, if we know we conceived a couple days after my cycle ended, would my baby be more likely to arrive earlier than someone who conceived a few weeks after their cycle? 

Just curious about how that works out since due date isnt based on day of conception.  

gollywollypog

In general ovulation occurs a little over halfway through your cycle.  If you have a normal cycle you won't conceive a week after your period starts, or a few days before your period starts.  Try this ovulation calculator:  https://www.ovulation-calculator.com/

kelnyc

You are NOT pregnant for 10 months (unless you actually live by the lunar calendar instead of the regular Gregorian one, which would be very unusal). 40 weeks does not equal 10 months because many months have more than 4 weeks. My cycle started on November 15, we retrieved the eggs on November 29 (which counts as ovulation/conception day) and I am due August 21st. If you count the months, it's only 9.

https://www.babiesonline.com/articles/pregnancy/a10monthpregnancy.asp

 

poison489

Due dates are not a definite, they are an estimate!

Many thing affect when your baby arrives.  If you have an unusually long or short cycle a doctor may use your conception date to calculate the due date. It is very rare for a woman to actually deliver on her "due date".   I believe it is less than 5% of women will have there baby on the 40 week date.  Most women go over the 40 weeks (average is 41 weeks and 1 day for FTM), and some will deliver early.

My conception date would give me a due date around September 23rd, and my LMP gives me a due date if September 29th.   With my first son I went in to labor on my conception due date and delivered on my LMP due date, three days later.  The doctors were pretty amazed. 

christyhal

Due dates are an estimate...very few babies arrive when they're scheduled to!  (Not that I am not still hoping mine decides to...LOL)

 

That being said, it is possible to have a big variation in due date based on LMP and due date based on ovulation.  My understanding is that LMP is used most commonly because that is the date most people will know, and the majority of people ovulate in the middle of their cycle.  Not everyone tracks/knows their ovulation date.  My LMP due date would have been Oct. 5 or 6, my ovulation due date was Sept. 30 or Oct. 1.  (I used OPKs.)  When I had my dating u/s in first tri, baby measured on track with the 9/30 date, so that is what my OB is going by.  If you've had a dating u/s then your doctor will usually go by how far along the baby measures if it is more than just a few days' difference from your LMP due date. 

ASmallWonder

Ok so first, like someone else said, you aren't pregnant for 10 months.  But yes, when you actually conceive can impact when you deliver but because not all babies cook for the "required" amount of time, there's no way to figure just how much of an impact your conception date will make, kwim?  A first trimester ultrasound is best at determining fetal age based on size and can give a better estimate of due date but still, it's up to your body.

aadewitt

Put it this way out of all the close friends I know who had kids (about 8 or so) only ONE had her baby on her due date.  All others were either earlier or later by just a day or two or by a week or so. 

So no a due date is just the time line of when baby COULD come, but she/he could come earlier or later.