Background: Controlled ovarian hyper-stimulation (COH) in combination with intrauterine insemination (IUI) has been shown to result in significantly higher pregnancy rates compared to un-stimulated (natural cycle) IUI . This may however not be true in all ages.
Methods: We performed a retrospective cohort study and analysed data collected prospectively on 1759 IUI cycles in couples with unexplained infertility. The results were analysed to show the outcome of IUI with COH, and IUI in natural cycle (unstimulated), in younger women compared to their older counterparts.
Results: In women age 37 and younger, COH resulted in a significantly higher pregnancy rate (13.0% vs 6.5%) and live-birth rate (10.7% vs 5.2%) compared to natural cycle IUI (p = 0.025, p = 0.045 respectively). However for older women age >37 years, natural cycle (unstimulated) IUI, resulted in a significantly higher pregnancy rate (12.0% vs 8.5%) live-birth rate (7.5%vs 3.5%) than IUI with COH ((p = 0.0037). This difference is even more significant when COH was performed with clomiphene citrate (7.5% vs 2.1%) (p = 0.0017).
Conclusion: COH was associated with a lower live birth rate in older women, irrespective of the agent used, and it seems to be worse when the anti-oestrogenic drug clomiphene citrate was used for COH. Older women may benefit more from natural cycle (unstimulated) IUI. A randomised controlled trial is required to confirm this observation.