Expert: Dorothy H, LCCE - 1/8/2010

Question
Hi Dorothy,
  Thank you for your answer. You mentioned that my cycle was off by 1-3 days. Before my lmp I had a 32 day cycle, so since the average cycle is 28 days, wouldn't that make my cycle off by 4 days? Also, since I did not get my period in November, hence the pregnancy test, could I possibly have ovulated earlier in October, and not necessarily have had a 32 day cycle like on the previous months? However, if I did ovulate earlier, say on October 19th (28 day cycle) instead of the 23rd (32 day cycle), I would imagine that the 6 week ultrasound would have read 6 weeks, 5 days, instead of 6 weeks 1 day. This is where I am still confused. Also, at this stage would an ultrasound be off by a month (or more)?

Answer
Hi Kaitlin,

It can get confusing!

An ultrasound would not be off by a month or more at any stage.  It can be 7-10 days off later on in pregnancy, but not a month.

Yes, it's certainly possible that you ovulated a little earlier in October - you may not have had a 32 day cycle that month.

If the ultrasound said 6 weeks 1 day, you were somewhere between 5 weeks 5 days and 6 weeks 4 days - with conception occurring between October 20 - October 26.  However, because sperm can live 3 days after conception (occasionally up to 5 days), it is possible that any time you had sex between October 15 and October 26 is what resulted in this pregnancy.

Some babies just take less time (or more time!) to "cook" - they may be completely ready to be born at 37 weeks, where other babies need perhaps 41-42 weeks to be ready to be born - a 4-5 week difference with babies conceived at exactly the same time.

I hope this helps clear things up in resolving your concerns.  If you have more questions, can you give me more details about what exactly you are concerned about with the conception date, (you can mark it private when you send it if you are more comfortable with that) I would be glad to try to help.

Sincerely,
Dorothy H, LCCE