['To evaluate pregnancy, delivery and neonatal outcome in singleton primiparous versus multiparous women with/without endometriosis.', 'Multicentric, observational and cohort study on a group of Caucasian pregnant women (n\u2009=\u20092239) interviewed during their hospitalization for delivery in five Italian Gynecologic and Obstetric Units (Siena, Rome, Padua, Varese and Florence).', 'Primiparous women with endometriosis (n\u2009=\u2009219) showed significantly higher risk of small for gestational age fetuses (OR: 2.72, 95% CI 1.46-5.06), gestational diabetes (OR: 2.13, 95% CI 1.32-3.44), preterm premature rupture of membranes (OR: 2.93, 95% CI 1.24-6.87) and preterm birth (OR: 2.24, 95% CI 1.46-3.44), and were hospitalized for a longer period of time (p\u2009<\u20090.0001) comparing with control group (n\u2009=\u20091331). Multiparous women with endometriosis (n\u2009=\u200997) delivered significantly more often small for gestational age fetuses (OR: 2.93, 95% CI 1.28-6.67) than control group (n\u2009=\u2009592). Newborns of primiparous women with endometriosis needed more frequently intensive care (p\u2009=\u20090.05) and were hospitalized for a longer period of time (p\u2009<\u20090.0001).'] Do women with endometriosis at first pregnancy have an increased risk of adverse obstetric outcome?