When should I take a pregnancy test?
If you're using an at-home urine test, the results are the most accurate about 1 to 7 days after missing your period, although it's possible to test positive before then. This is because in order for pregnancy to occur, a few important steps must come first: ovulation, fertilization, and a few days later, implantation of the blastocyst. A blastocyst is a fertilized egg, and its implantation into the uterine wall prevents you from having a period.
Pregnancy tests measure a hormone called beta-human chorionic gonadotropin, or beta-hCG, which doesn't appear until after implantation. This is why testing too early is more likely to result in a false negative. A false negative means the test incorrectly indicates that you're not pregnant, even though you are. During the first trimester, beta-hCG increases drastically, meaning the more time after conception, the more likely you are to see a positive result.
How do I calculate hCG levels from my last period?
hCG levels rise during pregnancy and can be estimated based on how many weeks have passed since the first day of your last menstrual period (LMP). Pregnancy is typically measured from LMP, with hCG levels rising rapidly in early weeks.
Since hCG levels vary widely, only a blood test can provide an exact measurement. If you’re tracking hCG for pregnancy confirmation or concerns, consult your healthcare provider.
How is pregnancy due date determined?
Your pregnancy due date, or estimated date of delivery (EDD), is calculated based on the date of your last menstrual period (LMP). This can be counter-intuitive, since fertilization generally occurs around the time of ovulation (about two weeks after your period).
Your due date is calculated by adding nine months to the first day of the last period, subtracting 21 days, then adding your previous cycle length. This method ensures accuracy by accounting for differences in menstrual cycle length among individuals.
EDD = LMP + 9 months - 21 days + previous cycle length
How is my due date calculated based on IVF transfer date?
To calculate your pregnancy due date for a fresh in vitro fertilization (IVF) transfer, your doctor typically adds 266 days to the date of egg retrieval or fertilization. For a frozen embryo transfer, the calculation depends on the embryo's stage at the time of transfer:
- If a day-3 embryo is used, the due date is 263 days from the transfer date
- If a day-5 blastocyst is used, the due date is 261 days from the transfer date
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