Uterine CD56 + cell density and euploid miscarriage in women with a history of recurrent miscarriage: A clinical descriptive study

In women with a history of recurrent miscarriage, the uterine CD56+ cell density in subjects with subsequent euploid miscarriage was significantly higher than those with subsequent aneuploid miscarriage. Both endometrial and embryonic factors should be investigated when interpreting uterine CD56+ cell density results relating to recurrent miscarriage. Recurrent miscarriage (RM) is an important clinical hurdle to overcome in the field of reproductive medicine and the causes of RM remain largely unknown [1]. Several previous clinical studies have shown an increased number of CD56+ cells in the peri-implantation endometrium in women with a history of RM [2-4]. Nevertheless, the prognostic value of uterine CD56+ cell measurement is still uncertain. Approximately 60% of spontaneous miscarriages are attributable to numerically abnormal chromosomes in the product of conception [5]. However, there are limited data addressing the relationship between the ploidy status of a subsequent miscarriage with endometrial factors in women with RM. The aim of this current study was to investigate whether or not the frequency of euploid miscarriage is increased in women with high preconception uterine CD56+ cell density. This is a prospective cohort study. It was approved by Joint Chinese University of Hong Kong- New Territories East Cluster Clinical Research Ethics Committee (Approval No.: CREC-2014.575). All the endometrial biopsies were collected using a Pipelle sampler (Prodimed, France) precisely on seventh day after LH surge of the peri-implantation period in the pre-pregnancy cycles, with written informed consent of the participants. A total of 182 women with a history of unexplained RM were recruited. Of them, 95 women became pregnant subsequently within 1 year following biopsy. Fifty-three women had a live birth and the other 42 women miscarried in the subsequent pregnancy. The mean ± SD age of all the subjects was 35.62 ± 5.09 years and the mean ± SD menstrual cycle length was 27.25 ± 2.32 days. Of these subjects, 128 women, 42 women, and 12 women had a history of three miscarriages, four miscarriages, and five or more miscarriages, respectively. There was no significant difference in the age or BMI between women who miscarried and women who had a live birth in the subsequent pregnancy. Routine G-banding chromosome analysis was performed in the products of conception from women with subsequent miscarriage. The results showed that 24 products of conception had a euploid karyotype analysis, of which 13 were male and 11 were female. The other 18 specimens were aneuploid, including 16 (89%) trisomies and two (11%) monosomies X. The most frequent trisomic was trisomy 22 (seven cases), followed by trisomy 16 (six cases), trisomy 4 (two cases), and trisomy 21 (one case). Immunohistochemistry staining was used to determine CD56+ cells in the endometrial specimens. The median uterine CD56+ cell density in women who miscarried (n = 42, median 3.09%, range 1.17–8.77%) was significantly (p = 0.035) higher than those who had a live birth (n = 53, median 1.95%, range 0.16–6.97%) (Fig. 1A). The median uterine CD56+ cell density in women with euploid miscarriage (n = 24, median 3.76%, range 1.25–8.77%) was significantly (p = 0.020) higher than those with aneuploid miscarriage (n = 18, median 2.21%, range 1.17–7.52%) (Fig. 1B). In addition, combining with our previous results derived from fertile controls [4], the median uterine CD56+ cell density in control women (n = 72, median 2.45%, range 0.92–5.33%) was significantly lower than RM patients with subsequent miscarriage (p = 0.040) and particularly those with euploid miscarriage (p = 0.024), respectively. However, the median uterine CD56+ cell density in control women did not differ significantly from those who had a live birth (p = 0.103) and those with aneuploid miscarriage subsequently (p = 0.089), respectively (Fig. 1). To further assess the confounding effect of maternal age, which is known to be a major determinant of aneuploid miscarriage [1], the correlation between age and uterine CD56+ cell density was also analyzed in this study. There was no significant correlation (r = 0.321, p = 0.195) between maternal age and uterine CD56+ cell density in women with a history of RM. Based on our previous work, using the result of 4.5% as the upper limit [4], 20 women were found to have a high uterine CD56+ cell density in this study. Among the women who had high uterine CD56+ cell density, the miscarriage rate (55%, 11 of 20) was not significantly (p = 0.274) different from women who had normal uterine CD56+ cell density (41%, 31 of 75). However, in the 42 women with subsequent miscarriage, the likelihood of a miscarriage being euploid among women who had high uterine CD56+ cell density (84.6%, 11 of 13) was significantly (p = 0.016) higher than that of women who had normal uterine CD56+ cell density (44.8%, 13 of 29) (Table 1). Our current study investigated the prognostic value of uterine CD56+ cell density in relation to the ploidy status of the embryo. We have included a relatively large group of subjects (n = 95) and showed that the uterine CD56+ cell density in women who miscarried again was higher than those who had a live birth in the subsequent pregnancy. Although there was a trend that women with high uterine CD56+ cell density had a higher likelihood of miscarriage, we failed to observe any significant correlation. Our results further supported the previous findings from Tuckerman et al. [3] that uterine CD56+ cell density on its own was not associated with higher miscarriage rate in a subsequent pregnancy. We also found that among women who had a further miscarriage, those with high uterine CD56+ cell density were more likely to have an euploid miscarriage. The observation can be explained by the existence of two main underlying causes of miscarriage, namely, endometrial defect and embryonic abnormality. In any given miscarriage, the identification of one underlying cause makes the other one less likely, although it is possible that occasionally both factors are present at the same time. In other words, the finding of an embryonic abnormality (aneuploidy) in a given case would make endometrial abnormality less likely, and vice versa. The hypothesis is consistent with our finding that high uterine CD56+ cell density (endometrial factor) is associated with a lower chance of aneuploidy (embryonic abnormality). The main clinical implication arising from our observation is that both endometrial and embryonic factors should be taken into account when investigating or interpreting uterine CD56+ cell density results relating to RM. At the very least, when a woman with a history of recurrent pregnancy loss miscarry again, every attempt should be made to find out the ploidy status of the product of conception. In conclusion, high uterine CD56+ cell density is associated with subsequent euploid miscarriage in women with a history of RM. Therefore, testing or treatment of high uterine CD56+ cell density is warranted in this cohort of women. This study was supported by Hong Kong Health and Medical Research Fund (04152786) and Shenzhen Key Medical Discipline Construction Fund (SZXK028). All the authors report no commercial or financial conflict of interest. The peer review history for this article is available at https://publons.com/publon/10.1002/eji.202048868. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.