Small gestational sac, slow hcg

hi i am in a similar situation as you. i just did my first scan and I was supposed to be measuring week 6 day 4 but my gestational sac measured only week 5 day 3. There was no yolk sac and heartbeat. Mine is a ivf case and the estimated date of week 6 should be very accurate and my doc said that I am measuring behind and advised that the pregnancy may not be viable. My betas were 169 and 1410 at 12dp5dt and 19dp5dt respectively and were low as per the doc. I am supposed to return for another scan next week. just wondering how did yours turned out if you don't mind sharing?

Did gynae count your pregnancy from last menstrual period (LMP) or last ovulation? If it’s LMP, it’s well known to not be accurate measurement especially if you have irregular periods. Better if it’s calculated from last ovulation - if you track it diligently all these while then it is more precise measurement of the true gestational age.