Q&A: My hCG levels are low. Did I have a miscarriage?

I can understand your concern—hCG (human chorionic gonadotropin) levels are an indicator first, that you're pregnant and second that the pregnancy is progressing normally or that something is amiss.

But one low hCG level is not as important to assessing the health of your pregnancy as a series. The general guideline is that the hCG should double every 48 hours or so in early pregnancy. Surely this "rule" softens the later into the first trimester you go, but combined with ultrasound, it's one of the major components of assessing fetal well-being.

There are, in fact, general "one-shot" levels that are expected within weeks of gestation, but since the last menstrual period is a good guess at gestational age (you may have merely had a delay in ovulation) the comparison of two 48 hours apart is your best bet.