It can be difficult to become pregnant with PCOS because it causes irregular ovulation. Medications to induce fertility when trying to conceive include the ovulation inducer clomiphene or pulsatile leuprorelin. Metformin improves the efficacy of fertility treatment when used in combination with clomiphene. Evidence from randomised controlled trials suggests that in terms of live birth, metformin may be better than placebo, and metform plus clomiphene may be better than clomiphene alone, but that in both cases women may be more likely to experience gastrointestinal side effects with metformin.