The levels of the hormone known as hCG (human Chorionic Gonadotrophin), change during the first trimester of your pregnancy. HCG levels are what are measured in order to determine whether or not you are pregnant. The hormone hCG is produced by cells that make up the placenta. The placenta, of course, is what provides nourishment to your baby after the fertilized egg becomes attached to the wall of the uterus.
Your hCG levels change dramatically during the first trimester. The levels of hCG are first detectable in your system somewhere around 11 days after your baby is conceived, but only through a blood test at this point. Over the next few days, between days 12 and 14 after conception, hCG can be detected in a urine test. Your hCG levels will double roughly every 72 hours through the first eight to twelve weeks of your pregnancy, and then will tend to decline afterwards, leveling off for the second and third trimesters of pregnancy.
HCG levels during the first trimester are measured in milli-international units per milliliter, or mIU/ml. The ranges of hCG levels during the first trimester can vary greatly from one woman to another, as well as from one pregnancy to another. In general, at around three weeks of pregnancy your hCG levels will be between 5 and 50 mIU/ml. At around the 4th week, hCG levels will be between 5 and 426 mIU/ml. At week 5, the range jumps to 18 to 7,340 mIU/ml. By week 6, it is between 1,080 and 56,500 mIU/ml. During weeks 7 and 8 of the first trimester, hCG levels will rise to between 7, 650 to 229,000 mIU/ml. HCG levels during the first trimester will peak sometime around 9 to 12 weeks of pregnancy, at somewhere around 25,700 to 288,000 mIU/ml. By the final weeks of the first trimester week 13 and 14, hCG levels are finally on the decline, and will be at around 13,300 – 254,000 mIU/ml.
If you are concerned about your hCG levels during the first trimester, and are worried that they may seem too high or too low, you should contact your health care provider. Your health care provider can help you to properly interpret those numbers, to know for certain if your hCG levels are where they need to be during the first trimester.