Pregnancy Duration & Ultrasounds: Accuracy in Early Abortion

Question
How does the abortion clinic determine how far along someone is?  Is the ultrasound accurate?  Or do they just base it on your last period?

Answer
Dear Beth,
This is an excellent question.  Ultrasound is the most accurate way to know the duration of the pregnancy.  In early pregnancy, ultrasound can determine the date of conception plus or minus 3 or 4 days.  In the United States, abortion clinics use ultrasound as the standard of care.  

It can be confusing, because doctors talk about how far along you are based on the first day of your last menstrual period, even though this is less accurate.  However, medical decisions are based on the ultrasound, not on dates.  For example, the abortion pill is only used until 9 weeks of pregnancy.  The doctor will use ultrasound to determine if you are eligible for the abortion pill.  

I hope this is helpful,
Doctor Joan
http://www.earlyabortionoptions.com
New York City