72 Chapter 4 Figure 2. The association between the predicted prognosis of natural conception and the estimated benefit of starting IUI-OS at different time points. The association between the predicted prognosis of natural conception and the estimated benefit of starting IUI-OS at different time points. This association is shown as cumulative probabilities over 6 months (y-axis) when starting IUI-OS, or not, at different time points after completion of the fertility workup (x-axis) for three example couples that have three different prognoses at time of hysterosalpingography (HSG): 40% (left), 32% (middle) or 25% (right). The prognosis was calculated over 1 year and updated after additional failed natural cycles. Grey bands represent 95% CIs. Left panel: Couple A is referred by their general practitioner, where the female partner is nulliparous and 32 years old, the couple has 1 year of subfertility at the time of completion of the fertility workup and the semen analysis showed 37% progressively motile sperm. Middle panel: Couple B has the same characteristics as Couple A except for 2 year duration of subfertility at the completion of the fertility workup. Right panel: Couple C has the same characteristics as Couple A but for 3.5 year duration of subfertility. In Figure 2, the absolute chance to conceive over 6 months decreased over time for expectant management, but not for IUI-OS, of which the absolute chance seemed much less variable between couples and timing of treatment start, at around 37%, 34% and 30% for the three couples. However, CIs were wide, especially for pregnancy chances after IUI-OS. The decrease in chances for expectant management over time led to a larger treatment benefit as IUI-OS was started later. It follows from Figure 2 that the prognosis for a couple does not have a large influence on the expected benefit in terms of the absolute difference between the IUI-OS and expectant management line as there was always a difference of 5% or more. This
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