Hi Sarah,
Your question is a good one!
There are so many variables with when to test. As you know conception occurs within 12 hours after ovulation. It then takes time for the cluster of cells to move down your fallopian tubes and land in your uterus. It then takes time for the cells to imbed in the wall of the uterus. Once this implantation has happened your body begins to produce HCG. Implantation occurs 4-10 dpo - with 4 being on the very early end of the scale and 10 being on the very late end of the scale. Each pregnancy for each woman is different. There is no 100 per cent accurate way of knowing when each pregnancy has implanted. Even ultrasonography in the days after conception isn't 100 per cent accurage with giving a definite "implantation day". It takes about 36 hours after implantation for enough hcg to be detectable in your blood to show *positive* and 48 to 60 hours after implantation for your urine to show traces of hcg. Even the amount of hcg is variable. Each pregnancy will show wide differences in hcg levels. The variance of normal is quite vast.

Some of the early detection tests can pick up a very tiny amount of hcg. This can be a good thing. It puts us out of our tww misery early. However as up to 30 percent of pregnancies end before 6 weeks it can also show a pregnancy that doesn't make it past more than a few days. This can be very upsetting for a woman who wants very much to have a baby. However it can also give us some information that may be helpful to carry a pregnancy to term...

I have had 8 pregnancies now and 4 live babies. With my dd3 I didn't show a positive until I was a day late for my period. The others I had a positive test a couple of days before my period was due.

Just last week I got a positive hpt only to bleed on Friday. I guess that has helped me to ask some questions about my cycle so it was a good thing in many ways. However my opinion (which is only mine and we all have differing views) is don't test early. Test when your period is due. YOu will then very likely get a nice strong positive line. No squinting at the line or holding it up to fluro tubes! Conversely if you get no second line you are probably not pregnant. No guessing no sleepless nights. It's yes or no.

It is always helpful to know that the symptoms many women experience before their period is due such as breast tenderness, reflux, constipation and even nausea are most likely due to the higher level of progesterone. When our period is due most women have 50mi/u of hcg in their urine. This isn't really enough to cause huge symptoms in most women.

I so so understand the impatience and frustration of the TWW. And it is true knowing about recurrent very very early loss or "chemical pregnancies" as they are sometimes called can help identify potential problems. But for most of us waiting until our period is due can just stop a lot of the frequent testing and disappointment at seeing only one line when in fact had we waited a day or two longer there would be two! Not to mention the money saved!

I wish you all the luck in the world this month. Keep us posted...