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Accuracy of pregnancy dating scans

accuracy of pregnancy dating scans-21

That one to two day window after your surge is the likely time you conceived.If you kept a basal body temperature chart (BBT) during the cycle you conceived, this is a useful tool to help pinpoint when you ovulated and therefore conceived.

You can estimate your date of ovulation and conception from the length of your menstrual cycle if this is fairly regular.By these facts: A conception date calculator can make it easier to figure out your date.The calculator below works for you if your menstrual cycles are regular and are between 24 and 38 days long.This calculation assumes the following: If your cycles are longer or shorter than 28 days, this method is less accurate.It is important to remember the lifespan of the egg and sperm can influence the date of conception.If you tracked these changes, the day before your mucus changed to a thick, tacky, cloudy, dried-up mucus was the day of ovulation, and your likely date of conception.

The day of ovulation, your mucus would have been at its most thin and watery, as well as clear and stretchy like egg white. Once your doctor or midwife gives you your due date, count 38 weeks back on a calendar to find your most likely conception date.

The day of your definitive positive reading is the day of the biggest increase in your LH.

This "LH surge" triggers ovulation and predicts it is likely to occur 24 to 36 hours later.

So, by this example you can understand you have a five day window during which you could have conceived.

If you were tracking other signs of fertility, such as basal body temperature charts, or ovulation predictor kits, they can help you narrow down your conception date to within one to two days.

The day of conception depends on: An obvious fact is you cannot conceive until you ovulate; therefore, the most likely date of conception is on the day of ovulation, if there is sperm around.