Background and objective: Previous studies did not draw a definitive conclusion about the influence of the role of deep endometriosis (DE) and ovarian endometrioma (OE) as risk factor for developing adverse perinatal outcomes in patients affected by endometriosis. This study aimed to investigate if adverse fetal and maternal outcomes, and in particular the incidence of small for gestational age (SGA) infants, are different in pregnant women with OE versus pregnant women with DE without OE. Material and methods: This study was based on a retrospective analysis of a database collected prospectively. The population included in the study was divided into three groups: patients with OE, patients with DE without concomitant OE, and patients without endometriosis (controls). The controls were matched on the basis of age and parity. Demographic data at baseline and pregnancy outcomes were recorded. Results: There was no statistically significant difference in first trimester levels of PAPP-A, first and mid-pregnancy trimester mean Uterine Artery Doppler pulsatile index, estimated fetal weight centile, and SGA fetuses’ prevalence for patients with OE, and those with DE without OE in comparison to health women; moreover, there was no statistically significant difference with regard to SGA birth prevalence, prevalence of preeclampsia, and five-minute Apgar score between these three groups. Conclusions: The specific presence of OE or DE in pregnant women does not seem to be associated with an increased risk of delivering an SGA infant. These data seem to suggest that patients with endometriosis should be treated in pregnancy as the general population, thus not needing a closer monitoring.