Also, no evidently elevated risk of congenital malformations was seen in infants born after PPOS treatment in comparison with the GnRH-ant treatment in both singletons (adjusted OR 0.81, 95% CI 0.47–1.41) and twins (adjusted OR 1.32, 95% CI 0.74–2.37). The gene discussed is GNRH1; the disease is pregnancy disorder.