Low Birth Weight Is Strongly Associated with the Risk of Deep Infiltrating Endometriosis: Results of a 743 Case-Control Study

The influence of intrauterine environment on the risk of endometriosis is still controversial. Whether birth weight modifies the risk of endometriosis in adulthood remains an open question. For this purpose, we designed a case-control study involving 743 women operated on for benign gynecological indications from January 2004 to December 2011. Study group included 368 patients with histologically proven endometriosis: 54 superficial endometriosis (SUP), 79 endometriomas (OMA) and 235 deep infiltrating endometriosis (DIE). Control group included 375 patients without endometriosis as surgically checked. Mean birth weights were compared between patients and controls, according to endometriosis groups and rAFS stages. Mean birth weight was significantly lower for patients with endometriosis as compared to controls (3,119 g ± 614 and 3,251 g ± 557 respectively; p = 0.002). When compared to controls, patients with DIE had the lowest birth weight with a highly significant difference (3,103 g ± 620, p = 0.002). In univariate analysis, patients with low birth weight (LBW), defined as a BW < 2,500 g, had a higher risk of endometriosis, especially DIE, as compared to the reference group (OR = 1.5, 95%CI: 1.0-2.3 and OR = 1.7, 95%CI: 1.0-2.7, respectively). Multivariate analysis, adjusted on ethnicity and smoking status, showed the persistence of a significant association between endometriosis and LBW with a slight increase in the magnitude of the association (aOR = 1.7, 95%CI: 1.0-2.6 for endometriosis, aOR = 1.8; 95%CI: 1.1-2.9 for DIE). In conclusion, LBW is independently associated with the risk of endometriosis in our population. Among patients with LBW, the risk is almost two-times higher to develop DIE. This association could reflect common signaling pathways between endometriosis and fetal growth regulation. There is also the possibility of a role played by placental insufficiency on the development of the neonate's pelvis and the occurrence of neonatal uterine bleeding that could have consequences on the risk of severe endometriosis.