Can Ultrasounds Be Wrong About the Sex of Your Baby?

Ultrasounds Wrong Sex Baby

When you a woman finds out she’s pregnant, one of the first thoughts that comes to her mind is, “Is it a boy or a girl?” And that is surely the first question that is asked by friends and family once the baby is born. So the desire to know the gender of your unborn baby is quite strong. For the last few decades, ultrasounds have been used to harmlessly and painlessly identify the gender of fetuses. But can they be wrong? And if so, does it matter?

How Accurate Are They?

Accuracy of ultrasounds depends on the gestational age of the fetus at the time of the ultrasound. Some ultrasounds are done very early, in the first trimester. In published studies, the ability to identify a gender has been reported to range from 64.6% of cases to as high as 90.5%,1,2 and as high as 97% at 14 weeks.3 The accuracy of the ultrasounds (getting the gender correct) at this age ranges from 87.5% to 99%.

And even more advanced techniques don’t guarantee success. Another study of 3D ultrasounds done between 9 and 13 weeks gestation correctly predicted the gender in only 56% of patients.

Further along in pregnancy, it becomes easier to identify the gender, and the accuracy improves. A study of ultrasounds performed at 20 weeks gestation, a common time for these studies, found that gender identification was possible in almost 90% of cases, with 97% accuracy.

Certainly, there are other reasons than gender identification for ultrasounds. These imaging studies are also done to get a good measurement of the fetal size, further delineate organ development, identify possible genetic problems in the fetus, and for other reasons.

So ultrasounds can provide a lot of information accurately, and for the most part, are reliable when it comes to gender identification, but they are not 100% accurate. The only truly accurate way to determine your baby’s sex is with invasive techniques, such as chorionic villus sampling or amniocentesis. These are not routinely done just for gender determination, but done to identify genetic diseases or conditions based on family history or results from other screening tests. You can read more about these tests here.

A noninvasive way to determine your baby’s gender is the cell-free fetal DNA testing. This is done to identify genetic diseases, such as Down syndrome. The test uses fetal DNA found in the mother’s blood to identify these diseases (and gender), but is not 100% accurate.

What Are The Implications Of Being Wrong?

You should remember, sometimes doctors want to know the gender of the fetus because some diseases are sex-linked, and if you are at risk for these diseases, identifying the gender is important. In these cases, it is imperative that the gender is identified correctly.

But for the vast majority of pregnant women, they just want to know. There are plenty of reasons for wanting to know the gender: to prepare better, especially if there are older siblings; to aid in family planning; to be mentally ready; and to just get to know the baby growing inside of you.

But when the gender is identified incorrectly, the effects can be profound, even when there are no sex-linked diseases to worry about. One study in Nigeria, where the culture has a high preference for male babies, found that incorrect gender identification (usually identifying a male fetus but a female was born) led to marital conflicts and even physical abuse of the mothers by their partners. Sixty percent of the women who had an incorrectly identified baby stated they had negative feelings about the newborn, and some of them wanted a reversal of the tubal ligation that was done at the time of the delivery.

In the US, there is not the same cultural pressure to have a boy, but there are still serious problems that occur when the gender identification is incorrect. One couple separated after getting an incorrect gender identification.

Take With A Grain Of Salt

So the lesson to be learned is that ultrasounds, like a lot of medical tests, are not 100% accurate. There are only two ways to get a completely accurate gender identification of your fetus, and those are invasive and not routinely done. So when the ultrasound tech tells you it’s a girl (or a boy), take that with a grain of salt.

Ruben Rucoba
Dr. Rucoba has over 25 years of experience as a primary care pediatrician after completing medical school at the University of California, San Francisco. His clinical areas of expertise include caring for children with special health care needs and assisting families with international adoption. He has been a freelance medical writer since 2010, writing for health websites, continuing medical education providers, and various print outlets. He currently works at Wheaton Pediatrics in the suburbs of Chicago, where he lives with his wife and four daughters, including a set of twins.

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