The Trying to Conceive and Just Starting Out Primer

This is a "primer" created by Krista (Rudylover) and posted by Jennifer (Tigger062077). We made this as a source of information for the "newbies" who are afraid to ask a "silly question"...and for the "oldies" who have been doing this so long they've forgotten the basics.

If you want to reach us, you can reach Jennifer at and Krista at

Tuesday, August 09, 2005

HPT's: Can They REALLY Detect Pregnancy 5 Days Early?

Many name brand HPT’s claim that they can detect the pregnancy hormone up to 5 days before AF is late. According to Dr. Amos Grunebaum (the fertility doc on WebMD), this claim is very misleading and does not hold true for many women. Note the claim always says “UP TO” 4 or 5 days early. Other pregnancy tests not designed for early detection say “AS SOON AS the first day of your missed period.” These HPT manufacturers are not guaranteeing they can detect pregnancy that early, just that they MIGHT – though many women do not understand that.

HcG is the hormone pregnancy tests detect. It is not produced until a fertilized egg implants in the uterus, and then it takes a few days before it can be found in the woman’s urine. Implantation occurs on average at 7-10 days past ovulation (dpo) – though some sources cite 6 – 12 dpo as a more reasonable range.

The average woman gets her period 15 days after she ovulates, which means her luteal phase is 14 days long. This is the kind of woman these tests base their claims on, and further they assume a fairly early implantation day. Many women don’t have a 14 day LP. Most women have an LP of 12 – 16 days actually – though some can be shorter and some can be longer. Testing that early for women with shorter than average LP’s would almost never yield a positive result.

Let’s say that a woman with that “gold standard” 14 day LP became pregnant and her fertilized egg implanted at 7 dpo. If she took the HPT 5 days early, she would still only have a few days for the hCG to build up. She may or may not get a BFP even if she was pregnant depending on how much hCG was present in her urine at that time. (Technically this is not a false negative. Negatives are only truly false if the hCG in the urine is above the level that the test detects and it reads negative.)

If you have trouble dealing with BFNs it is always best to wait until you are sure you are late to test (which you may not know if your cycles are unpredictable, unless you are charting). Even then, there is no guarantee that the hormone level is high enough to show up positive on the HPT. Different brands detect different levels of the hormone, and women produce it at different rates too. If you have questions about HPT’s and how they work, is a very helpful website with a lot of information.