Question: I found out I was pregnant via home pregnancy test when I missed my period but was having lots of menstrual cramps - test said 2-3 weeks pregnant (which is the timeframe I was thinking). I went to urgent care the next morning for the cramping - they did an intravaginal u/s and they said they could not see anything in the uterine cavity, but thought I may have a corneal ectopic pregnancy. My hcg level was 551. Two days later, another u/s still showed questionable corneal ectopic, but they thought that they saw a 'small gestational sac' (I'm unsure of the size), so they were leaning towards not ectopic. Hcg was 1057. Two days later, hcg was 2766, and they ruled out corneal ectopic. However, they said that the 3rd u/s showed that my sac is 44mm (with probable yolk sac, and no fetal pole). I also have a collapsed cyst on my left ovary. They told me it will probably be a blighted ovum, and I need to do a viability scan in two weeks. I am confused, because I thought the sac grew approx 1mm/day. So how come they could not see the sac on the first ultrasound, see apparently a small one two days later, and then two days later see a 44mm one? Am I wrong and I am possibly 9/10 weeks pregnant (instead of approx 5 weeks), or is it possible there is a mistake in the measurement of 44mm???
i am worried about how big the sac is, because I know that 44mm with no fetal pole will be a blighted ovum. But is it possible to miss such a large sac on the first u/s? Also, I'm concerned that the cyst is collapsed - will that contribute to miscarriage? Any help would be appreciated, because I cannot wait 2 more weeks for another scan wondering about this.

Hi Dr. XXXXXXX

Thanks for your answer. I totally understand what you are saying about the sac not being visible until about levels of 1500. I also understand if the sac is empty at 44mm, it is most likely a blighted ovum.

However, can a sac grow that fast - ie. Friday - not visible, then following Tuesday (4 days later) at 44mm? I thought that the sac grows approx 1mm/day?

Also, if my timing is right, the Tuesday ultrasound (where they say my sac is 44mm), I would only be 4 weeks, 6 days since LMP. Is that even possible to have a sac at a size of 44mm this early?

I think my confusion lies in how fast the sac apparently grew, and how much it grew in the timeframe that I believe I conceived. Could you shed some more light on that?

Thanks so much.

Would 4.4mm be more typical of an almost 5 week gestation?