| For a pregnancy test to become positive, the | | | | Implantation, the attachment of the fertilized egg |
| fertilized egg has to first implant into the uterus | | | | in the lining of the uterus, occurs on average |
| and then send enough amounts of hCG the | | | | about a week or later after ovulation/fertilization, |
| pregnancy hormone into your blood stream for | | | | but it can happen as early as six days and as late |
| enough hCG to create a positive pregnancy test. | | | | as 12 days after fertilization/ovulation. At the time |
| Implantation, when the fertilized egg implants into | | | | of implantation, the placenta starts making the |
| the endometrium, happens about a week after | | | | pregnancy hormone hCG, which then enters the |
| ovulation (range: 6-12 days), and it takes another | | | | blood stream. hCG can be detected in the blood |
| 3-4 days after implantation (9-10 dpo: days after | | | | about three to four days after implantation. Urine |
| ovulation) for the blood pregnancy test to first | | | | hCG can be detected about two to three days |
| become positive. | | | | after blood hCG can first be seen. Detection of |
| - Blood Pregnancy test: If you are pregnant then | | | | hCG depends on timing of implantation, so hCG |
| the blood pregnancy test is usually positive within | | | | can normally be detected in the blood between |
| 3-4 days after implantation or about 9-10 days | | | | nine and 16 days after ovulation (HPT: 12-19 days |
| after fertilization and ovulation. | | | | after ovulation). |
| - Urine (Home HPT) Pregnancy Test: The urine | | | | 2. Blood hCG Level |
| pregnancy test will usually not become positive in | | | | There is a wide normal variation of hCG levels, |
| most women until a missed period or about a | | | | both in the blood and the urine. If a woman has |
| week after implantation. Many manufacturers of | | | | low blood hCG levels, for example, then it can |
| urine pregnancy tests want you to believe that | | | | take several more days for it to show up on a |
| the urine test is usually positive before a missed | | | | pregnancy test. |
| period, but only about 25% of pregnant women | | | | 3. Urine hCG Level |
| will test positive with the HPT 2 days before a | | | | Urine hCG levels change over the course of the |
| missed period, and about 40% the day before | | | | day depending on how much you drink and how |
| the missed period. The wide variation when the | | | | diluted or concentrated the urine is. Urine |
| urine pregnancy test becomes positive is due to | | | | pregnancy testing is best done with more |
| four variables which determine when the home | | | | concentrated urine. If you drink a lot of fluid, the |
| urine pregnancy test becomes positive: | | | | urine may be too diluted early on in pregnancy to |
| | | | achieve an hCG concentration adequate enough |
| 1. Timing of Implantation | | | | for a positive test. |
| 2. Blood hCG levels | | | | 4. Sensitivity of Urine Home Pregnancy Test |
| 3. Urine hCG level (eg.how concentrated or diluted | | | | Different pregnancy tests have different |
| the urine is) | | | | sensitivities. The lower the sensitivity, the earlier a |
| 4. Sensitivity of the pregnancy test | | | | pregnancy test becomes positive. Sensitivities are |
| 1. Timing of Implantation | | | | indicated in mIU/mL, the lowest amount of hCG in |
| A pregnancy test detects the presence of the | | | | the urine that tests positive. A sensitivity of 20 |
| pregnancy hormone hCG (human chorionic | | | | mIU/mL requires one-half the hCG level to be |
| gonadotropin) either in the blood or in the urine. | | | | positive when compared with a 40 mIU/mL |
| The hCG in the urine comes from the hCG in the | | | | sensitivity level, and it may become positive |
| blood after it was filtered through the kidney. | | | | several days earlier than the pregnancy test with |
| After ovulation, the egg gets fertilized and travels | | | | a higher sensitivity. Make sure you read the |
| through the fallopian tube toward the uterus. This | | | | package of the pregnancy test to determine your |
| travel takes on average about a week. | | | | pregnancy test's sensitivity. |