Some experts think it's because a woman is less likely to ovulate while she's breast-feeding.

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Dr Phillips said Sophie would still be able to have children when she is older, as her remaining ovary will compensate for the one that was removed meaning she will ovulate and have periods as normal.

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Women with reasonably regular cycles are likely to be the most likely to benefit from this - those with erratic menstrual cycles or who do not ovulate at all are unlikely to be suitable for natural cycle treatment.

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