Understanding a Low HCG Level of 16: What It Means & Next Steps

Question
I went to the doctor on 7/2 for my annual pap.  I was suppose to start my period that day.  It would have been exactly 28 days.  I had spotting on 6/30 only when I wiped and it went away so the doctor did a urine/pg test and it came back positive.  He sent me to do an HCG level it came back at 16.  I went back on 7/5 for another hcg level and am still waiting for those test to come back but I got a message from the doctor saying that 16 was very low and I would probably miscarry.  Is this true even if I got the test done on the day that I was suppose to start my period.  I am very early.  We have been trying to get pregnant for about 8 months and have gotten false positive home pregnancy test.  I just want this one.  I do have two boys already and had a miscarriage inbetween them at 7 weeks.  My second little boy was born extremely premature at 25 weeks but my oldest little boy was full term.  Thank you for your time, let me know if you have any questions.

Answer
Dear Bernadette,

If the test was done at 28 days into your cycle, or approximately 14 days past ovulation (DPO), your hCG level would indeed be a bit low. An average would be about 25 mIU/ml at 10 DPO, 50 at 12 DPO, 100 at 14 DPO. However - hCG levels are not going to begin registering until implantation occurs. Implantation can occur anytime between 6-12 days after conception/ovulation. So, if implantation occurs late, hCG levels would obviously be getting a slower start. The bigger piece of information will be whether that hCG is doubling every 48 hours. That is a much better indicator as to the health of the pregnancy.

I hope this has helped you and answered your question. I wish you well.

Brenda