curious about due dates

nodito · August 2013

Are women who ovulated and conceived later in their cycles more likely to go past the 40 week due date? Like, if a woman knows she always ovulates on day 21, should she consider her due date to be a week later than the one calculated using LMP? Just curious.

JCWhitey · August 2013

It has nothing to do with that. The baby will come hen the baby comes. The baby may come at 36 weeks or 42 and there's really no reason for shen they choose to come (if not forced out). Also not all due dates are calculated by LMP. Mine was based off a dating ultrasound which was pretty accurate to when I'm pretty sure we conceived. He was still born at 38 weeks.

aylafsu88 · August 2013

The Dr uses your LMP to determine a due date but that date assumes that you ovulated at day 14 in your cycle. Many woman ovulate around that day (i.e. +/- a few days. Most of the time those couple of days wont make a huge difference. If you are someone who ovulates later in your cycle like day 21 and you have longer cycles it could affect your date. However, I think that is why they routinly do dating ultrasounds now. The early ultrasounds are pretty accurate at estimating how far along you are. I have heard of doctors changing due dates based on these ultrasounds. The big thing is that these due dates are just estimates. Some babies come early and some come late. I O around day 14/15 in my cycle and I went into labor at 38 weeks 4 days.

boogerbearoriginal · August 2013

If your due date is based on LMP, and the woman knows she ovulated that much later than the 14day average, then her due date is going to be off but there will be other signs things are off, like baby measuring a week behind the whole pregnancy.

But like PP mentioned, 40wks is just an estimated arrival day and while an accurate due date is important for tracking the pregnancy to ensure things are developing normally, it is not a good gauge of when baby will actually be delivered.

If you chart or known to have long cycles, I would mention this to your Dr so they can account for that when calculating due date. A few days off won't be a big deal but once you get 7+days later it can be significant in terms of how your pregnancy is managed.

Another thing to consider, there is also a range of normal implantation and fetal growth so again, a few days +/- isn't significant in the grand scheme of things.

robyn2201 · August 2013

Because I have wonky cycles and know from charting and temping that I tend to ovulate later (between CD 22-25), my OB's have not gone off my LMP when calculating my EDD's. We did an early u/s to determine my EDD's with both babies.

tokenhoser · August 2013

I lied about my LMP so that my due date would be closer; I did ovulate late in my cycle and rather than have that conversation with my doctor and roll the dice on her believing me or giving me the "oh, don't worry it doesn't matter much" line... I just took the date 14 days before my ovulation and used that as my LMP.

I stand by it. It doesn't matter until you're talking induction and then it matters A LOT. There was really no need for an extra ultrasound; I knew when I conceived.

hilwithonelary · August 2013

tokenhoser said:

I lied about my LMP so that my due date would be closer; I did ovulate late in my cycle and rather than have that conversation with my doctor and roll the dice on her believing me or giving me the "oh, don't worry it doesn't matter much" line... I just took the date 14 days before my ovulation and used that as my LMP.

I stand by it. It doesn't matter until you're talking induction and then it matters A LOT. There was really no need for an extra ultrasound; I knew when I conceived.

I agree. I hate the "it doesn't matter... The baby will come when the baby wants to come" argument I ovulated on day 42 with DS. I gave the OB my LMP and tried to show her my chart. She completely ignored my chart and insisted on using my LMP. She did an initial exam and thought my uterus was smaller than it should be (duh!). She acted very worried and concerned and set up a dating ultrasound. The dating ultrasound gave me a due date 6 days earlier than it should have been. This was within the accepted margin of error for when it was performed, but at the end of pregnancy, those days can matter. I was very worried about being pushed for induction because they thought I was further along than I was. I ended up going early, so luckily that didn't matter. I ovulated on day 20 with DD. I lied about my LMP even though I went to a CNM instead of my old OB. I have no regrets. There was no arguing about due dates, which I'm very thankful for considering I had DD at 41w1d. Yes, your due date is an estimate, but in this age when inductions for being overdue are often pushed on women, I think it's very important to have as accurate a due date as possible.

cyclek8bride · August 2013

I had a mw tell me it's a due month not a due date. The day given is just in the middle of that month.

tokenhoser · August 2013

cyclek8bride said:

I had a mw tell me it's a due month not a due date. The day given is just in the middle of that month.

And she'll probably want to induce you at the end of that month.

Getting the right month matters.

Arielle27 · August 2013

I have longer cycles and knew my ovulation date with my first two. Still, one was born at 39+ weeks and the other at 37+ weeks. Like other women here have said, that week won't make much of a difference when the baby could come anywhere within a 4-5 week window.

hilwithonelary · August 2013

I think there are two separate issues being discussed here. 1) Your due date isn't a magical eviction date. You should not have an expectation that you will deliver exactly on it. There is a window of 3 weeks before and 2 weeks after that is considered normal. Try not to get too stressed if you go past your due date, which I know from experience is easier said than done. In this sense, no, your exact due date doesn't really matter. 2) Many OBs and MWs get very antsy after the due date, especially as you get closer to 41 weeks. Some are more comfortable up to 42 weeks. But at some point, they are all talking induction (including most homebirth MWs who will transfer care after a certain point). In this sense, yes, your due date does matter. Personally, I would want the most accurate due date possible so that I'm not pressured for induction sooner than I feel necessary. Since due dates from LMP are based on a day 14 ovulation, it makes perfect sense to me to adjust your due date if you know you ovulated on a different day.

atcwag · August 2013

I have regular cycles. By my LMP, my EDD was 9/30, however my OB did a routine dating U/S (it was between 7 and 8 weeks I believe...or maybe just after 8 weeks) and that moved my EDD to 10/2. 2 days not really a big deal, but I'll take as many days as I can get to avoid the "induction" talks if baby decides to stay put a little longer.

sschwege · August 2013

tokenhoser said:

I lied about my LMP so that my due date would be closer; I did ovulate late in my cycle and rather than have that conversation with my doctor and roll the dice on her believing me or giving me the "oh, don't worry it doesn't matter much" line... I just took the date 14 days before my ovulation and used that as my LMP.

I stand by it. It doesn't matter until you're talking induction and then it matters A LOT. There was really no need for an extra ultrasound; I knew when I conceived.

This is what I plan to do next time, lie about my LMP date.

I charted before getting pregnant with both my babies. With DD I ovulated on cycle day 21, so a difference of a week. Brought my chart in MW confirmed it and we went with an EDD that reflected that. Second time ovulated on CD 22, brought my chart in again MW didn't even look at my chart and asked me if I was willing to do a dating u/s since I had been BFing when I got pregnant. I had already had an u/s in the emergency room for a 'threatened m/c', so we went with that date (basically a difference of two days). I had both my babies at 40w3d (charting dates). Next time I'm just going to lie because it was really disheartening that they wanted a dating u/s, when I know what I'm doing and my date is the most accurate.

When the induction drums start beating it can make a difference!

sschwege · August 2013

Here's another reason it can make a difference. With DD I was always measuring two weeks behind (just a tape measure). My MWs told me that within two weeks is not a problem, but anymore than that and they want to watch more closely. Had I gone with my LMP date I would have been averaging three weeks behind and they might have been thinking there was a problem when in fact there was not.

mysticl · August 2013

On each of my ultrasounds DS measured about a week older than he was. When they started using the tape measure I was always at the top of the "normal" range for how far along I was. However, they never changed my due date. I was induced due to high blood pressure 2 days prior to my due date. At that time I was only about .5cm dilated which tells me if I had been able to go into labor on my own it would have been past my due date. So if they had changed my due date and I hadn't had the blood pressure issues I may still have ended up induced because I would have been considered "over due". And I am 100% certain about my conception date.

huntjul · August 2013

tokenhoser said:

I lied about my LMP so that my due date would be closer; I did ovulate late in my cycle and rather than have that conversation with my doctor and roll the dice on her believing me or giving me the "oh, don't worry it doesn't matter much" line... I just took the date 14 days before my ovulation and used that as my LMP.

I stand by it. It doesn't matter until you're talking induction and then it matters A LOT. There was really no need for an extra ultrasound; I knew when I conceived.

I did this also because between temping, charting, and using ovulation tests, I knew better than the LMP did, and it DOES matter in the end if you carry to 41/42 weeks and face an induction. My anatomy scan later dated the pregnancy 1 day from when my charting did.

memo9 · August 2013

tokenhoser said:

I lied about my LMP so that my due date would be closer; I did ovulate late in my cycle and rather than have that conversation with my doctor and roll the dice on her believing me or giving me the "oh, don't worry it doesn't matter much" line... I just took the date 14 days before my ovulation and used that as my LMP.

I stand by it. It doesn't matter until you're talking induction and then it matters A LOT. There was really no need for an extra ultrasound; I knew when I conceived.

I lied about my LMP with my first pregnancy too. I o'd on cd75.... that would have totally blown their minds. This pregnancy I actually o'd on cd14 (or somewhere pretty close) so I didn't have to lie. Go figure!

ETA: DD was born at 40 weeks 3 days.

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