We determined whether maternal Il11 expression is required for fertility by mating homozygous (Il11−/−) female mice with male mice of variable Il11 genotype (Il11+/+, Il11+/− or Il11−/−) and found that female mice deficient for Il11 never had a detectable pregnancy nor gave birth to offspring (Fig. 2B), which mirrors the infertility phenotype of homozygous Il11ra1−/− female mice5. Here, IL11 is linked to Infertility.