Ultrasound diagnosis of endometrial polyps in pregnancy

Endometrial polyps are benign focal overgrowths of the uterine mucosa. They are a recognized cause of abnormal vaginal bleeding and have also been associated with subfertility and early pregnancy loss1,2. The ultrasound features of benign polyps in non-pregnant women have been well-documented3, but there have so far been no reports of endometrial polyps identified on ultrasound examination during early pregnancy. In this report, we describe 10 cases of endometrial polyps diagnosed in the first trimester and followed-up during pregnancy (Table 1). In nine women (Cases 1–9), a solid hyperechoic structure was seen protruding into the uterine cavity adjacent to the gestational sac on the first scan (Figure 1). In the remaining case (Case 10), the polyp was first diagnosed at a follow-up examination at 12 weeks. It was located below the placenta with a well-defined feeder vessel. In nine cases, the polyp had an appearance typical of a benign lesion. One polyp (Case 3) appeared as a cystic structure adjacent to the gestational sac, which was suspected initially to be a complete hydatidiform mole (Figure 2). Serum beta-human chorionic gonadotropin (β-hCG) level at 13 weeks' gestation was 179 233 IU/L or 2.5 multiples of the median. Maternal serum β-hCG levels decreased between 13 and 20 weeks, whereas the focal cystic structure remained of similar size at the periphery of the placenta. Blood supply to the lesion decreased after 13 weeks and the final diagnosis of an endometrial polyp was made. In two cases (Cases 3 and 10), the polyp was identified at birth attached to the placental membranes, and their benign nature was confirmed on histopathological examination. We also compared the size of the endometrial polyps in pregnancy to the findings obtained in a cohort of 41 randomly selected premenopausal non-pregnant women with endometrial polyps. The median diameter of the polyps detected in pregnancy was 14.7 (interquartile range (IQR), 9.0–23.4) mm, which was significantly larger compared with the 7.3 (IQR 5.5–10.4) mm in non-pregnant women (Z-score, −3.440; P = 0.0006). Our case series shows that some endometrial polyps can be detected on ultrasound examination during the first trimester of pregnancy. This is a novel observation and we have not found any previous reports in the literature describing ultrasound diagnosis of endometrial polyps in early pregnancy. Differential diagnosis of a focal lesion in the endometrial cavity during early pregnancy includes submucous uterine fibroids, focal adenomyosis, ‘chorionic bump’4, multiple pregnancy combining a normal gestational sac with retained products of conception, or a complete hydatidiform mole. The other possible rare diagnosis is mesenchymal dysplasia of the placenta. We found that five of nine women in our series who wished to continue with their pregnancy had a healthy baby at term. This finding supports the view that endometrial polyps may not be associated with impaired implantation and placentation, and are not a major risk factor for early pregnancy failure or subsequent placental insufficiency5. Women should be advised that their pregnancy could develop normally despite the presence of a polyp and that they should continue with their routine antenatal care. A follow-up scan may be arranged once the pregnancy is completed to check for their presence and consider surgical removal.