[sara~b]

Excerpt:

Results showed that the overall success rate of gender identification between 12 and 14 weeks was 80% which is less than invasive karyotyping. In the transverse plane, male fetuses showed a dome shaped genital swelling with a cephalic-directed phallus and females had three or four parallel lines representing the labia. The gender of the fetus did not affect the operator’s ability to assign gender and when assignment was possible gender did not affect the accuracy. The ability to assign gender increased with increasing gestational age.

Another article, Determination of gender - 10 and 14 weeks by Z Efrat et al which appeared in the Journal: Ultrasound in Obstetrics and Gynecology 1999; 13:305–30, reported:
The 172 women were all scanned transabdominally. Using a midline sagittal scan with the fetus supine and the spine parallel to the transducer face (sound lines perpendicular) ‘without extension of the spine or limbs’, angles were drawn on an image of the genital area with a line through the genital tubercle and another through the lumbosacral skin line. Male fetuses were characterised by an angle >300 (angle increases with age) and a females by parallel or convergent lines (angle <300). In other words, the phallus was vertical/cranially directed in males and caudally directed in females. At 12 weeks the accuracy of gender assignment was 98.7% and at 13 weeks the accuracy was 100%. There was incorrect assignment of males as females in 3% at 12 weeks and no females assigned as males after 12 weeks. The authors therefore conclude that ‘a final decision on invasive testing for sex-linked conditions should be undertaken only after 12 weeks of gestation’.
The Genital tubercle angle has now been increasingly used as an accurate method for diagnosing fetal gender at around 12-13 weeks during a scan for the Nuchal translucency.

Source: Ultrasound diagnosis of fetal gender

So I guess this means if my tech was any good then there is an 80%+ chance my baby really is a girl! How cool!

[Chelnae6]

Sweet! I know a lot of people find out the gender when they get an NT scan around 11-13weeks. I think its by blood or something like that.

[LisanAndy]

What an awesome article TFS Sara!

[sara~b]

Originally Posted by ~ChelNae6~

Sweet! I know a lot of people find out the gender when they get an NT scan around 11-13weeks. I think its by blood or something like that.

The blood tests are for downs and trisomy 18. They look at the sex plate during the ultrasound which begins to differentiate in boys and girls around week 10. From what I've been reading a decent tech and cooperative baby means that they are right more often that not!