Spontaneous twin pregnancies occur in about 1 out of every 250 pregnancies. A real world clinical question has to do with dating a spontaneous twin gestation: Do we use the smaller crown rump length or the larger for dating in the 1st trimester? Do we use the smaller or larger measurement of biometry in the 2nd trimester? We had this discussion today in our prenatal clinic, and in true form and fashion, I turned it into an episode! PLUS, there is practice guidance from Jan 2025 (ISUOG) to settle the debate. Listen in for details.