I know, you have been told to wait until 16, 18 or 20 weeks to find out if it’s a boy or a girl. I know that your sister found out at 14 weeks and it was wrong.
Ultrasound is very operator dependent. No two sonographers will get the exact same image. Most sonographers have never utilized nub theory at 13 weeks. Some will correctly guess all boys ( boys can be easier) but guess wrong on girls. Some rely on the between the legs shot:
This can be somewhat unreliable, especially at 13 weeks.
Here’s what I did: I read a pretty informative article about “nub theory” which explained how the angle of the genital tubercule could be used to determine a boy or girl. It made logical sense to me. The genital tubercule of the female is aligned parallel to the body, and is receding inward ( known as the clitoris) and the genital tubercule of the male is angled at 30 degrees or more from the spine ( known as the penis in that case). I then offered my patients at 13 weeks an educated guess of what the gender was…and I WAS NEVER WRONG. 200 correct consecutive “GUESSES”. I knew then that I had developed my skill. Upon further research, I found that other countries in the world use the “nub theory” routinely!
Check out this clinical study from 1999 ( when ultrasound was still unrefined and blurry, compared to today)
First-trimester determination of fetal gender by ultrasound.
Abstract
OBJECTIVE:
To assess the accuracy of fetal sex determination at 11-14 weeks of gestation.
METHODS:
Fetal gender assessment by ultrasound was prospectively carried out in 172 singleton pregnancies at 11-14 weeks of gestation immediately before chorionic villus sampling for karyotyping. The genital region was examined in a midsagittal plane and the fetal gender was assigned as male if the angle of the genital tubercle to a horizontal line through the lumbosacral skin surface was greater than 30 degrees and female when the genital tubercle was parallel or convergent (less than 30 degrees) to the horizontal line.
RESULTS:
The accuracy of sex determination increased with gestation from 70.3% at 11 weeks, to 98.7% at 12 weeks and 100% at 13 weeks. In the male fetuses, there was a significant increase in the angle of the genital tubercle from the horizontal with crown-rump length. Male fetuses were wrongly assigned as female in 56% of cases at 11 weeks, 3% at 12 weeks and 0% at 13 weeks. In contrast, only 5% of the female fetuses at 11 weeks were incorrectly assigned as male and this false-positive rate was 0% at 12 and 13 weeks.
CONCLUSION:
The clinical value of determination of fetal sex by ultrasound is in deciding whether to carry out prenatal invasive testing in pregnancies at risk of sex-linked genetic abnormalities, because invasive testing would be necessary only in pregnancies with male fetuses. Our results suggest that a final decision on invasive testing for sex-linked conditions should be undertaken only after 12 weeks of gestation.
- Wow, even in 1999 they were still getting great results at early ultrasounds! Why doesn’t your ultrasound tech know about this? Because these studies were done in London. Another reason that you won’t get a lot of cooperation out of a sonographer in a hospital or outpatient setting is that we don’t care about the gender. We have bigger fish to fry, and the gender is a distraction. Our main concern in that setting is making sure your baby is healthy, and not missing anything. Here at Wonder Time, I am happy to do only “the fun stuff” and I am confident in my gender determination!
- Read more here.
