Elevated latent prenatal steroidogenic activity has been found in the amniotic fluid of autistic boys, based on measuring prenatal androgens and other steroid hormones. To date, it is unclear if other prenatal steroids also contribute to autism likelihood. Prenatal estrogens need to be investigated, as they play a key role in synaptogenesis and corticogenesis during prenatal development, in both males and females. Here we test whether levels of prenatal estriol, estradiol, estrone, and estrone sulfate in amniotic fluid are associated with autism, in the same Danish Historic Birth Cohort, in which prenatal androgens were measured, using univariate logistic regression (n = 98 cases, n = 177 controls). We also make a like-to-like comparison between the prenatal estrogens and androgens. Estradiol, estrone, estriol, and progesterone each related to autism in univariate analyses after correction with false discovery rate. A comparison of standardized odds ratios showed that estradiol, estrone and progesterone had the largest effects on autism likelihood. These results for the first time show that prenatal estrogens contribute to autism likelihood, extending the finding of elevated prenatal steroidogenic activity in autism. This likely affects sexual differentiation, brain development and function.