at my 20-week scan LO was very shy had legs tightly crossed, they said possibly a girl, but sounded VERY unsure. we had to go back the next week because LO wasnt letting her do all the anomaly checks lol. at the next one we asked again and she still wasnt certain but thought it looked like a girl.
we wanted to kno for sure coz we needed to choose a name and wanted to buy pink stuff but held back as we werent certain, so when we heard innervision doing free gender scans we went at 33-weeks; we saw a big close up in 3d of our baby's 'lady lips'! so they were right at 20-weeks definately is a girl!