what does a long cycle do to due date?

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what does a long cycle do to due date?

Postby summerdawnc » Tue Feb 14, 2017 7:07 am

My cycles are 41-42 days, what effect does this have on my pregnancy? Should I go by conception date or LMP?
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Re: what does a long cycle do to due date?

Postby erin860 » Tue Feb 14, 2017 9:33 am

When you have your first ultrasound the technician will measure the baby and be able to tell how far along you are by the size of the baby. You're due date is always based on your last monthly period but during this ultrasound if the baby is measuring a week larger or smaller they will change your due date anything less than a weeks difference they will keep your due date as based on your last monthly period. It is helpful to know if you ovulated super late though because when you go in for the ultrasound and the baby is only measuring six weeks when it should be eight weeks you will know why and won't need to worry that the baby is not thriving. In this case the doctor will probably have you come back for additional ultrasounds most likely the following week.
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Re: what does a long cycle do to due date?

Postby summerdawnc » Wed Feb 15, 2017 1:17 pm

Thank you Erin! So the ultrasound measurement is most accurate?
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Re: what does a long cycle do to due date?

Postby erin860 » Wed Feb 15, 2017 1:37 pm

Yes, the ultrasound measurement is most accurate. Your baby will still be a little bigger/smaller so it might not tell you exactly to the day when you conceived but it will be very close. If you have 40 day cycles, I'm sure the tech will change your due date at your first ultrasound. Congratulations on your pregnancy!
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Re: what does a long cycle do to due date?

Postby Happyfroggy » Wed Mar 01, 2017 3:57 pm

I wanted to add, in some places like where I am, they never seem to want to do early ultrasounds. They always just want to go by the archaic method of period date alone which is fine but in your case, your cycles are long enough that it will make your due date way too early which can be problematic if you go 'over' and they are pressuring to induce but you know you aren't actually over.

So what to do? Well, I normally don't advocate lying, but if you know your ovulation date, lie to match your period up to it! This will get you the most accurate due date estimate if an early ultrasound isn't available or if one is but they insist on going by calendar. Basically all you need to do is give them the date exactly two weeks before ovulation. So say your period was Jan 1st but you didn't ovulate until CD22. Instead of telling them your period started Jan 1st, just lie and say it started January 8th.

I know this advice seems bizarre but I did this for my son and I'm glad I did. He was born the day before his due date. If I had given them my 'real' period date they would have put the due date a week earlier and I would have been pressured to induce. He was 6.5 lbs at birth.

Unfortunately, a lot of doctors are CLUELESS about charting ovulation and are very stuck on the calendar method. That's why if you just want to save yourself the grief of arguing, just adjust your period date to match your ovulation date. It's more accurate and you wont' be pressured to induce early based on dates alone.

Edited to add: ultrasound dating scans are most accurate the earlier they are when individual size variations haven't come into play yet.
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Re: what does a long cycle do to due date?

Postby summerdawnc » Wed Mar 08, 2017 6:57 pm

I wish I had done that - so they would have done an accurate due date. I can't imagine it would swing me more than 1 week, but I am 37 weeks and already 1 cm dilated, so I am hoping baby comes on her own and there won't be any medical reason to interfere. But next time, I will know better. I was just starting to get the hang of charting and voila! :)
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Re: what does a long cycle do to due date?

Postby tryingnumber3 » Thu Mar 16, 2017 11:57 am

If your cycles are normally longer because you ovulate later, then you would be not as far along in reality than as to the standard 28 day cycle they use to calculate due dates. If you had an early ultrasound, then go off that. If not, the based off lmp may say you're 40 weeks for example, but because of late ovulation may only be really more like 39.
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