Miscarriages are generally not caused by healthy sperm. Most miscarriages occur due to genetic abnormalities or issues with the developing embryo. However, certain lifestyle factors, health conditions, or exposure to harmful substances can potentially affect sperm quality, which may indirectly influence pregnancy outcomes. Both partners need to maintain a healthy lifestyle and seek appropriate medical care when planning to conceive or if experiencing recurrent miscarriages to address any potential factors that might affect fertility and pregnancy.