It’s a big decision whether or not to find out whether or not you are having a boy or girl at your ultrasound visit. If you have decided yes, it’s a big deal in the ultrasound room, waiting for the sonographer to break the big news. Once it is revealed, most people get excited but then they wonder if there is room for error. Even if it looks pretty convincing during your scan, afterwards chances are your friends and relatives will have stories to cast doubt on whether or not what you’ve been told is actually right.
So, if you’ve been told boy versus girl, can you bank on it? The answer is a somewhat unsatisfactory “Yes, MOST of the time…”
Why the ultrasound might be wrong:
- Experience of the sonographer- You hope that whoever is doing your ultrasound is well trained with hundreds, if not thousands, of hours of supervised experience. Ultrasound is not as easy as it might look, and it can be easy to be fooled regarding gender if you are not properly trained. Girls have surprisingly prominent yet normal genitalia, which can sometimes be easily confused as ‘boy bits’ by someone without experience. Umbilical cord can also play tricks on a newbie, making a girl look like a boy.
- Too early to call: One of the most common reasons for error is making the gender call too early. I have seen many cases where even the most experienced and respected high risk perinatologists have been wrong (and I must admit I have similarly misled families on a couple of occasions) because we predicted gender at the 12 week nuchal translucency scan, only to discover the error at the 20 week anatomy scan (click for more info on what happens at these scans). A complete discussion on what fetal gender looks like at 12 weeks, including images, can be found in the post “Am I having a boy or a girl?” . The essential truth is that boys and girls look VERY VERY similar and BOTH have an external phallus at this point in development. Despite what boys and girls “should” look like at this scan, not all of them are blatant or clearly defined and predictions made at this early scan ALWAYS have some wiggle room for a mistake. Predictions at the 18-20 week scan are much, MUCH more reliable. In fact, as long as you have an experienced sonographer, you can count on what they tell you to be true more than 99% of the time. Why only 99+% and not 100%?? Because some fetuses can have ambiguous fetal genitalia…
- Ambiguous fetal genitalia: While not common, it is not completely unusual for fetuses to have abnormalities of the genitourinary tract, especially in boys, which can make an accurate determination of their gender difficult even after birth. There are also multiple cases reported where, in perfectly normal girls, there is a temporary hypertrophy or enlargement of the clitoris and/or labia (which may or may not be related to hormonal imbalances), but which do regress to normal appearances before birth or in the first year of life. In these cases, it is possible that a girl fetus could be mistaken for a boy. Additionally, there are some rare fetal chromosomal abnormalities and androgenital syndromes which can cause confusion regarding boy versus girl genitalia.
Fortunately, in the vast majority of cases, as long as you get your prediction at 18 weeks or more, your baby is almost certainly what you have been told. If you happen to have multiple scans as your pregnancy progresses, you should be able to throw out any lingering doubt that you may have. The good news is that in this day and age, if you want to know what you are having, you can do so with a high level of confidence.