Hi, ultrasound on 26.9.2013, 6w5d, 8.4mm. cycle 33days. lmp 5.8. i had sex on 20.8 and 28.8. which date is more likely a conception date? jana

Too close to call: If it matters which is the conception date, a woman must always separate her possible conception dates by at least 2 weeks... Which means planning ahead every time. With a 33 day cycle, or with a 6 week 5 day ultrasound estimate of gestational age, "the day" is estimated to be august 24. So, this is too close to call. Life is not exact.

August 24th!: If the fetus is growing at an 'average' rate, it actually was conceived on 8/24. If the only two opportunities to conceive were 8/20 and 8/28, the baby could be either, depending if it is growing a little slowly or a little quickly, or even if the ultrasound is a few days off. In the end, there is no way to know for sure. With a long cycle, i recommend setting the due date as 5/17/2014.