Does the Use of Ovulation Monitors Really Increase Pregnancy Rates? Some Things Women Should Know
Ovulation monitors are widely used by women wishing to achieve pregnancy. However, there are few data substantiating claims that these devices enhance the probability of becoming pregnant. In one report it is concluded from the cumulative pregnancy rate that the use of the Clearblue Easy Fertility Monitor increased the pregnancy rate. In a second report, it is argued that the use of the Clearblue Digital Ovulation Test reduces the time taken to conceive. We reconsider these previously published data by analysing each cycle and show that use of such devices might have a small effect (ϕ ≈ 0.12, odds ratio = 2.1-2.2, relative risk = 1.9) in the first month of use, but has no significant effect (ϕ ≈ 0.01, odds ratio = 1.2, relative risk = 1.1-1.2) in the second month. However, the subjects recruited for these two trials had single cycle pregnancy rates (7-11%) that were more similar to those of women avoiding pregnancy (about 6%) than women trying to conceive (about 25%). Given this, there is a reason to suspect that the data that are available might not be representative of all women. Further work is required to test whether even this small transient effect can be replicated in women with higher pregnancy rates. Women should be aware of the limitations of these ovulation monitors.