Are you pregnant but not sure exactly when you conceived? Ultrasound is the most accurate way to determine how far along you are in your pregnancy. An ultrasound provides images and measurements of your developing baby that can help estimate how many weeks pregnant you are.


The first way to find out your conception date is to determine when you were last ovulating. In general, women can only conceive when they are ovulating — that is, when their ovaries release a new egg into their fallopian tubes for fertilization. That means you can use your ovulation dates to determine when you became pregnant.

Ovulation usually occurs about two weeks after your menstrual period and lasts for two or three days. This means you can sometimes determine when you conceived based on your ovulation cycles — simply determine when your last menstrual period was, and add approximately two weeks.

However, this method isn’t always accurate. Not all women have the same cycles of menstruation and ovulation. Some women’s menstrual cycles are irregular. Others have ovulation periods closer to or further from their menstrual period. Some women aren’t sure when their last period was. In other words, calculating conception based only on your body cycles can be difficult.


Another way to learn your conception date is to determine the last time you had sexual intercourse. Unfortunately, this method isn’t totally accurate either. Conception is a process and takes time. A man’s sperm can stay alive inside your body for up five days after sex.

This can make it difficult to determine when you conceived, especially if you have had more than one partner during the time when you ovulated. Also, remember that you could become pregnant even if you or your partner used birth control since no method of birth control is 100% effective at preventing pregnancy.


The best way to determine how far along you are (gestational age), etc. is with a pregnancy confirmation ultrasound. Early pregnancy ultrasounds can determine the age of your growing baby and estimate when you likely conceived.

The earlier an ultrasound is performed, the more accurate the measurements will be and the more likely you can determine how far along you are. This method of determining how far along you are (gestational age), etc. can be more accurate than date-based calculation, especially for women with irregular periods or who don’t know their last menstrual period date.

Learn more about your pregnancy and schedule a no-cost and confidential ultrasound.

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