Pregnant or empty sac?

I am 27 years old with 2 normal, full term babies. I have normal periods for the most part, however I am uncertain of the first day of my last period but I am certain the first day I'm able to recollect was Feb. 3. On March 4th I took 3home pregnancy tests & confirmed it at the health dept on the 5th of March. The nurse came in and stated I was "definately" pregnant but was only by a urine sample. I've been sick with flu like symptoms and when it got really bad I went to the ER where a blood test and vaginal ultrasound was done. There hcg level was 32,390 but when the ultrasound was done they could not detect a fetal pole or heartbeat however there was a sac that was estimated to be at about the six week size. I was strongly advised to make an appointment with my ob/gyn inwhich I saw first thing this morning. She did a yearly pap smear & physical exam w her hands and detected no problems. The lab said my hcg levels were at 38,000(blood was drawn approximately @ noon & yesterday approximately @ 6pm.) They have yet to find a fetal pole or heartbeat but I dont know how much the levels should go up or when I should be extremely concerned that the sac is indeed empty?

[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. Fetal heart beat usually appears by 8-9 weeks. 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 levels. If they rise and almost double in 48 hours, then chances of pregnancy carrying forward are high. Please discuss with your gynecologist. Take care!