Could the Ultrasound Be Wrong about Baby's Gender?

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Can an ultrasound be wrong? Do you worry about ultrasound gender mistakes? Ultrasound in midpregnancy is frequently used to tell the sex of the baby by having the ultrasonographer (sonographer) scan for the baby's genitalia. At this point they will announce, "It's a boy!" or "It's a girl!" Though for some families, this statement turns out to be wrong.

Could the ultrasound be wrong about baby's sex?

Yes. Does it happen frequently? It's hard to track. How does it happen? Here are a few examples:

Too Early

The best time to be able to determine the sex of your baby is between 18-20 weeks. Ultrasound done before this relies not on external genitalia but on the direction of the genital tubercle. Ultrasound done after this point risks being crowded out as the baby grows.


Not all ultrasound machines are created equally. In fact, some ultrasound machines are simply very old and may not give the best views.

Baby Doesn't Cooperate

Let's face it, not all babies are exhibitionists. I've heard many a mom say, that baby simply wouldn't show off for the sonographer. If that happens, the determination of girl or boy may be made on poor images from a positioning point of view. It is also harder to tell the sex of the baby if the baby is in a breech position, has their legs crossed, hands near their genitals, etc.


We've all heard the old joke about the baby girl being called a boy because she had the umbilical cord between her legs, but there is truth to the topic in that an inexperienced sonographer can make a mistake. An experienced sonographer can too, but they are less frequent.

Maternal Weight

It's a simple fact that if you are heavier, ultrasound image quality is less clear.

This can cause difficulty in scanning.

There are plenty of reasons why it may happen, some of which you have control over. So, don't push the envelope and try to schedule the ultrasound appointment early just because you're anxious. You risk getting information that isn't right. Ask about the equipment and the experience of the ultrasonographer. As for baby's cooperation...good luck on that one. Though some ultrasonographers recommend you drink a caffeine free carbonated sugar filled drink before the ultrasound to get your baby active.

When Mistakes Do Happen

You can imagine the shock, disappointment and even grief that parents feel when their dream baby boy or girl isn't born, but another baby. It takes many people a while to recover from this shock. In fact, one small study showed that when women experienced the wrong sex prediction it lead to more than just a distrust of ultrasound; some also experienced marital strife and domestic violence. The earlier the mistake is discovered the easier it can be to shake it off say some.

It's okay to feel horribly about this, despite what others may tell you. One mom referred to it as a mental miscarriage. She said it wasn't that she didn't love the baby who was here, but it simply wasn't the baby she's been dreaming about and getting to know for the last nine months. It took her a few weeks to reconcile the new baby with her dream baby.

Other families are able to laugh it off and move on. There is no one way to deal with it. The key is simply being true to yourself.

B J Whitlow et al, "First trimester diagnosis of gender" which appeared in the Journal: Ultrasound in Obstetrics and Gynecology 1999; 13:301–304.

Chigbu CO, Odugu B, Okezie O.Int J Gynaecol Obstet. Implications of incorrect determination of fetal sex by ultrasound. 2008 Mar;100(3):287-90. Epub 2007 Nov 26.

Odeh M, Granin V, Kais M, Ophir E, Bornstein. Sonographic fetal sex determination. J. Obstet Gynecol Surv. 2009 Jan;64(1):50-7.

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