Questioni found out i was pregnant at 6 weeks but every ultrasound after tha is of by a 1 week or 2 ...how can i find out what date i conceived?
AnswerCrystal,
To calculate your conception date, you will need to know how long your cycles typically are and at what point in your cycle you usually ovulate. However, if you do not track your ovulation date by using an ovulation predictor, saliva microscope or fertility charting, then it may be impossible to determine exactly when you conceived.
The length of a pregnancy is typically measured from the first day of your last period or by early ultrasound (between 7-10 weeks). Using the date of the last period is only accurate if your cycles are 28 days apart and you ovulate on day 14. If you have long cycles or ovulate late, then you would not be as far along as you thought.
Conception usually occurs around 14 days before the end of your cycle, but can vary from 9-16 days. The time after ovulation but before you begin your next cycle is called the luteal phase and is typically the same length, give or take a day, from cycle to cycle.
This means that if your luteal phase is usually 14 days and your cycles are usually 30 days apart, you most likely conceived on day 16.
Early ultrasound measurements taken between 8-10 weeks are very accurate. They are typically only off by a day in either direction. This means that if an ultrasound showed you to be 6 weeks pregnant, you could either be 5 weeks, 6 days or 6 weeks, 1 day pregnant.
In the beginning of pregnancy, all babies develop at much the same rate. This rate begins to change dramatically for each baby after the first 12 weeks. So, the further into a pregnancy an ultrasound is performed, the less accurate it becomes. If your ultrasounds have been after 20 weeks of pregnancy, then it is not unusual for them to be off by a few days to a week or even two. This is especially true if your cycles are much longer or shorter than average. Much can depend on the quality of the equipment, the position of the baby and placenta, level of fluid, and the skill of the technician.
So, if your measurements have been off, it can mean that your baby is growing more quickly or slowly than other babies, you have more or less fluid than usual, or the baby is in a difficult position to measure.
You can use the due date calculator at http://www.givingbirthnaturally.com/calculating-due-date.html to help you determine when you conceived if you have a good idea of how long your cycles typically are and when you usually ovulate.
Best,
Catherine
