Naturally, most women want to be absolutely certain that they’re really having a miscarriage before making decisions about treatment, but on rare occasions, doctors misdiagnose viable pregnancies as miscarriages.
With something as important and devastating as a miscarriage diagnosis, it’s normal to want to be 100 percent sure of the diagnosis before moving forward. With any medical problem, a misdiagnosis is a theoretical possibility.
Miscarriage is no exception. Technically speaking, medical or laboratory errors could theoretically lead to a misdiagnosis of pregnancy loss at any point in pregnancy – but this is uncommon.
Most doctors use established guidelines before diagnosing miscarriage. And when evaluated by these guidelines, generally laboratory and imaging results are considered reliable and accurate for diagnosing pregnancy loss.
Now and then, however, miscarriage misdiagnosis does occur. When it does, the situation almost always involves a few specific situations.
In early pregnancy, the embryo grows larger every day and being off even by a few days with the dating can make a difference in the measurements and in whether or not first-trimester ultrasound will detect a fetal heartbeat. Women who have irregular menstrual cycles or who were uncertain about their dates may have normal pregnancies that could initially be mistaken for missed miscarriages when the ultrasound does not show the expected development counting from the last menstrual period.
Most doctors avoid the possibility of miscarriage misdiagnosis by ordering a follow-up ultrasound to check for continued development whenever there’s any uncertainty about dates in an early pregnancy. When a pregnancy is viable, the gestational sac and embryo will be considerably larger after a week (the usual interval for a follow-up scan), but a nonviable pregnancy will show either no growth or minimal growth.
Misdiagnosis of pregnancy loss from confusion about dates affecting ultrasound results is specific to early pregnancy. Ultrasound is increasingly reliable for diagnosing pregnancy loss as pregnancy progresses. Once the gestational sac and baby have reached a significant size, ultrasound findings can definitively diagnose miscarriage.