No apparent heartbeat..

Dear all, I'm a bit worried with the following. My last period was on the 22nd of July and had a spotting on the 27th of August. Since I am rather irregular and stopped taking the pill only 4 months ago (after some years), I found that normal. I got a positive test on the 29th of August and went to the doctor immediately. He told me I was running my 6th week of pregnancy already (which I found a bit too much due to not being regular with my period). On the 13th of September (yesterday) I did my first US and the tech couldn't find any heartbeat. She decided to do an intra vaginal one and said she could see the pregnancy and the baby but no heartbeat so far... She seemed quite negative about it - though I told her there could be a miscalculation of the weeks. I don't know what to think. She told me to come in one week and I am quite worried and sad about all this... Could it be normal not to see the baby's heartbeat by now? If it is a miscarriage, what should I expect from the next days? All my (healthy) pregnancy symptoms remain - I'm rather tired, feeling sick in the morning, my breasts remain bigger than before...
Thank you for your help!

[Dr. Kokil Mathur]

Hi!
Normally a gestational sac with a yolk sac appears at about 5 weeks (calculated from your last missed period date) of pregnancy and can be well visualized by 6 weeks on a transvaginal (through a vagina) ultrasound (so it can be missed at 5 weeks), when you can see a fetal pole too. Fetal heart beat usually appears by 8-9 weeks. This is why it is best to repeat the scan a week or two later.
At times the sac appears but there is no baby inside. This is called blighted ovum. This is confirmed if an ultrasound through vagina reveals a sac with gestational sac diameter greater than 13 mm and no yolk sac, or diameter more than 18 mm with no embryo. Follow-up ultrasound is done after 10 days to verify diagnosis. Normally it is wise to wait until 10-11 weeks of pregnancy for a confirmed diagnosis of blighted ovum or fetal death. Meanwhile monitor the HCG levels at 48 hours intervals. If they rise and almost double in 48 hours, then chances of pregnancy carrying forward are high. Please discuss with your gynecologist. Take care!