Q: What is HCG?
A: HCG is a hormone made by the placenta. HCG levels surge in the first trimester of pregnancy and is detectable in your urine within a day or two of implantation -- so when you pee on a home pregnancy test you're actually measuring your HCG levels. "What makes HCG so interesting is that there is a huge range of what's normal when it comes to this number," says Dr. Hakakha. In normal pregnancies, she notes, it's likely that there is a such a wide range because different women have different placentas, each with different functional abilities.
Q: What patterns do HCG levels maintain during pregnancy?
A: Although most hormones increase at the beginning of pregnancy and continue to rise throughout the 40-week journey, HCG is different. From the time your baby is conceived until 10 weeks of gestation, your HCG levels rise rapidly, doubling every two to three days, but then the levels begin to fall. "This means that at the beginning, your number might be two. It'll then move to four, eight, and 16, and then it really picks up speed, moving into the 25,000 to 50,000 range," says Dr. Ross. "When it gets to 100,000, it turns around and goes down again. For the rest of your pregnancy, your HCG level will likely remain at 10,000."