Sonogram - no fetal pole or pulse

Julia
Any of you ladies had a sonogram and not been able to see the fetal pole or pulse early on but then seen it a week or two later? 
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​I had my 1st sonogram last Friday at about 6 weeks, there was the yolk sac but no fetal pole or pulse. The doctor said it's either a very early pregnancy or a non viable one.
​I'm going for another sonogram and won't know until then.