Do ovulation predictor kits actually help?
Probably a little, on the strength of one trial, and only in a specific group.
This has been reviewed systematically: 7 randomized trials, 2,464 women or couples.
For urine ovulation tests, the LH strips sold in every pharmacy, live birth was higher: relative risk 1.36, with a 95% confidence interval from 1.02 to 1.81. The reviewers translated that into absolute terms themselves: if the chance of a live birth without urine ovulation prediction is 16%, the chance of a live birth with urine ovulation prediction is 16% to 28%.
Three restrictions travel with this result, and they are usually dropped:
It applies to women under 40 who have been trying for less than twelve months. That is the population studied. It has not been shown in women aged 40 and over, and it has not been shown in couples who already meet the definition of infertility.
Apps and cervical mucus tracking are not the same thing. For fertility awareness based methods the point estimate for live birth was 0.95, with a confidence interval spanning both directions, at low certainty. The evidence is for the strips, not for the calendar.
Nobody has properly studied the downside. All the evidence on stress and strain from timed intercourse is very low certainty from single small trials. The honest statement is that the psychological cost is unmeasured, not that it is absent.