EVERYONE Thought I'd share the finding of this study that looked at various methods women use to predict the day they ovulate - incluing OPK sticks and charting. The link to full write-up is here.
The study is very interesting: they used 101 women from infertile couples who were scanned (ultrasound) throughout one cycle. Of those 101 cycles, ovulation was confirmed in 97 of the cases.
LH sticks indicated a surge in 100 of the 101 cycles. In three cases, despite a positive surge, there was no evidence of ovulation by ultrasound. This doesn't surprise me because LH surge is just your body trying to ovulate.
They also asked the women to chart. 11 of the cases were not 'assessible', they don't say why but I assume some of the women couldn't manage to do it properly through the cycle so their charts discounted.
In the other 90 women, BBT showed a biphasic pattern in 69 cycles (68.3%) and a doubtful or monophasic pattern in 21 cases - or 20.7% of the study!. Ultrasound correlated with BBT charts in 65 of the ovulatory cycles, and 2 of the anovulatory cycles.
The day that people ovulated according to charting is a bit more of a concern. In the cases in this study, they found a wide variability between when charts say people ovulated and when ultrasound say ovulation happened: "ranging from 8 days before to 4 days after ovulation".
If I am understanding this correctly, I assume it could mean that if my chart says I ovulated on CD14, I might actually have ovulated anywhere between CD6 or even up to CD18. (I can't work out how many women were 'off' with their charts so don't know how common this out of synch thing is).
They conclude that BBT is a good method for confirming ovulation (i.e. you see a biphasic pattern), but less reliable for nailing down the actual day of ovulation.
I thought I'd share - basically, I think that if we use charting alone, you need to SWI for at least 8 days before your chart usually says you ovulate, and keep going for 4-5 days after to be damn sure you were busy at the right time.
I use a CBFM and charting, and in most of my cases they correlate and I have assumed I am in synch. But I now wonder if I actually ovulate later than my charts say, and DH and have always stopped SWI'ing one day after the spike ... I wish I'd found this study earlier to cover all bases.