Materials and method

We searched the PubMed database for studies on adverse pregnancy outcomes and endometriosis published until August 2022. Our research is focused on miscarriage, spontaneous preterm birth, obstetric hemorrhage, preeclampsia and small for gestational age. Only English language meta-analyses, systematic studies and cohort studies were included. We also present examples of endometrial lesions found in pregnancies that were admitted to the University Emergency Hospital in Bucharest.

Results and discussion

1. Endometrioma

Many articles have been published along the years about endometriosis and pregnancy, but the information is difficult to categorize due to the large heterogenicity of studies and patients’ particularities. Endometriotic lesions change their appearance during pregnancy, therefore it is sometimes difficult to diagnose them correctly. The study of Ueda et al. (2010) states that in 0.5-1.2% of pregnancies, an ovarian cyst is diagnosed, but from those cysts, only 0.05-0.5% are endometriomas. The imaging aspects of endometriomas in pregnancy are different from the ones outside pregnancy due to decidualization. Sonographers may find typical or atypical cysts. Typical lesions are round cysts, with a minimum diameter of 10 mm, with thin, regular borders, with a mild echoic homogenous content, with diffuse echoes but no papillary formations. Atypical lesions are uni- or multilocular cysts, with a mild echoic content or with a “broken-glass” like structure, with vascularized intracystic papillae and a thin contour. In addition to ultrasound, MRI can be used, but biomarkers are not recommended⁽³⁾. A large study published in 2015 by Maggiore et al. searched for cases of decidualized ovarian endometriosis. The meta-analysis contained articles from 1998 to 2015, but with a small number of patients. Most cases were patients who were not diagnosed with endometriosis prior to pregnancy and the lesions had an atypical imaging aspect, due to which MRI and CA125 were used for the differential diagnosis. Moreover, clinicians opted for surgical cyst removal in pregnancies under 22 weeks. Complications derived from endometrioma are part of the differential diagnosis of pelvic pain during pregnancy. Acute abdomen can occur due to torsion of enlarged cysts, rupture or infection (Maggiore et al., 2016)^(1,4,5). In Figure 1, we show the ultrasound image of a large endometrioma.

Besides ovarian endometriosis, pregnant patients may have superficial lesions or deep infiltrative lesions. Deep endometriosis is the most severe phenotype, with lesions that penetrate more than 5 mm under the surface of peritoneum, uterosacral ligaments, the ureter, bladder, and intestine, with or without occlusion or hydronephrosis. Extrapelvic endometriosis is pleural, umbilical, neural or diaphragmatic. Endometrial tissue that infiltrates in the myometrium is diffuse or focal adenomyosis, which is independently responsible for pain, bleeding and infertility. Peritoneal endometriosis can mimic carcinomatosis and bladder endometrioma must be differentiated from benign or malignant bladder tumors and calculus. Diffuse bladder endometriosis affects 1% of pregnancies. It rarely invades bladder serosa^(6,7). In Figure 2, we show the intraoperative image of a patient with deep endometriosis and adherences.

2. Gastrointestinal

Studies of Setubal et al. (2014) and Villa et al. (2008) found that intestinal endometriosis is present in 5-12% of women with endometriosis. Spontaneous intestinal perforations were described in the third trimester of pregnancy or in the immediate postpartum period. Adhesions and extensive decidualization that weakens intestinal wall are possible pathological mechanisms^(8,9). Acute appendicitis with peritonitis is rare, but possible (Glavind et al., 2018)⁽¹⁰⁾.

3. Vascular

A very rare complication is spontaneous hemoperitoneum in pregnancy (SHiP). Only 20 cases were published in the literature. Bleeding occurs from pelvic endometriotic implants or ruptured vessels in the posterior uterine wall or in the parametrium. Maggiore et al. (2016) and, recently, Lier et al. (2017) found that most cases are described in the third trimester or in the postpartum, and in 94.5% of situations it led to emergency explorative laparotomy and caesarean section^(1,11). In Figure 3, we show the intraoperative image in a patient with deep endometriosis and hemoperitoneum.

4. Uterine

Spontaneous uterine rupture was described in very few studies and is especially associated with previous surgery for endometriosis. The posterior uterine wall and lower segment are affected⁽⁹⁾.

5. Urinary system

Uroperitoneum is very rare, being reported by Chiodo et al. (2015) and Maggiore et al. (2008). The extensive decidualization of severe deep endometriosis with serosa perforation can cause urohemoperitoneum^(4,12). In Figure 4, we show the ultrasound image in a patient with stage IV endometriosis, bladder endometrioma and a positive pregnancy test.

6. Ectopic pregnancy

Recent studies comprising meta-analyses of cohort and case-control studies found an increased association between endometriosis and ectopic pregnancy. Interestingly, they could not find sufficient data to draw conclusions about the stage or type of endometriosis, mode of conception and ectopic pregnancy⁽³⁾.

7. Spontaneous abortion

Studies published in the 1980s suggested that women with endometriosis had an increased risk for miscar­riage, but with conflicting results. Recent studies found an increased risk for miscarriage as well, but confounding factors, such as assisted reproductive techniques (ART), adenomyosis and other causes of infertility, were mentioned. Vercellini et al. studied 928 patients and concluded that women with adenomyosis had a 31% increased risk for miscarriage and women without adenomyosis had a 14% increased risk^(7,13). Saraswat et al. studied a large cohort of 14,655 patients and found that women with endometriosis had a significantly increased risk for spontaneous abortion compared to those without endometriosis⁽¹⁴⁾. Horton et al., in a more recent and elaborated study, concluded that women with adenomyosis and endometriosis had an increased risk for miscarriage compared to controls⁽¹⁵⁾. The latest ESHRE Guidelines recommend clinicians to be aware of this risk, although the recommendation is based on low/moderate quality data⁽²⁾.

8. Preterm birth

Women with endometriosis were more likely to have premature rupture of membranes and preterm birth, according to larger studies published between 2009 and 2019 (Fernando et al., 2009; Horton et al., 2019). This was observed in both women with and without ART, but definite conclusions cannot be drawn^(15-17).

9. Placenta praevia and obstetric hemorrhage

Placenta praevia was described in many studies about endometriosis in pregnancy. A possible explanation might be an alteration of uterine contractions in women with endometriosis which leads to abnormal blastocyst implantation. Horton et al., in 2019, found that antepartum hemorrhage is with 80% more frequent in women with endometriosis⁽¹⁵⁾. Healy et al., in 2010, concluded that women with endometriosis had a 1.7-fold increased risk for placenta praevia. In more recent studies, the results are contradictory⁽¹⁸⁾. Maggiore et al., in 2016, found no association between endometriosis and placental abruption and antepartum hemorrhage⁽¹⁾. Horton et al. (2019) and Lalani et al. (2018) concluded that the risk is increased for placental abruption, but not in postpartum hemorrhage in women with endometriosis compared to controls^(15,19). In Figure 5, we present the intraoperative image in a pregnant patient with deciduosis and endometriosis lesions.

10. Intrauterine growth restriction (IUGR), small for gestational age (SGA) babies and neonatal complications

The studies of Fernando et al. (2009) and Conti et al. (2015) report a two-fold increased incidence of SGA babies in women with endometriosis compared to controls. The possible explanations were placental insufficiency and abnormal placental implantation^(17,21). Larger studies, on more than 1.5 million pregnancies (Exacoustos et al., 2015; Stephenson et al., 2016), did not find an association between SGA and endometriosis⁽²¹⁾. Mochimaru et al. (2015) found an association between SGA and adenomyosis⁽²³⁾. Recent studies (Horton et al., 2019) did not find an increased risk of SGA and endometriosis⁽¹⁵⁾.

11. Caesarean section

The latest studies found that the incidence of cae­sarean section is higher in women with endometriosis, possibly due to previous surgical interventions, labor dystocia, malpresentation and ART (Exacoustos et al., 2016; Horton et al., 2019)^(15,22). Clinical experience shows that caesarean scar endometriomas are also encountered in some patients with endometriosis who give birth by caesarean section. These patients usually address their physician after two or more years after surgery to investigate the appearance of a round, painful mass located under the scar tissue. In Figure 6, we present the postoperative image of an endometriosis lesion located on the caesarean scar two years after the patients’ first birth by caesarean section.

Conclusions

Endometriosis remains one of the main causes of chronic pelvic pain and general discomfort for women. In clinical practice, patients with a wide range of symptoms, apparently unrelated to a gynecological sub­strate, actual­ly have endometriosis. There is an increased need for a wider approach of the disease, considering that these women come not only with pelvic pain, but with infertility and psychological problems, as well. Pregnancy is not a cure for the disease, and the new ESRHE Guidelines recommend clinicians not to induce this idea. Pregnancy modifies the aspect of endometriotic lesions and, in some cases, results in adverse outcomes. When possible, it is better to diagnose and approach the lesions before obtaining a pregnancy. The new ESHRE Guidelines, based on clinical findings, recommend clinicians and patients to be aware that complications induced by endometriosis during pregnancy are indeed rare, but potentially severe. To this date, there is no specific protocol for the pregnancy with endometriosis, but more studies are needed to improve the management and quality of life of these patients. 

Conflict of interests: The authors declare no conflict of interests.