Study on the Association Between SXCI and RM and the Possible Genetic Mechanism

Recurrent spontaneous abortion (RSA), defined as 2 or more consecutive pregnancy losses before 20-22 weeks of gestation, is a multifactorial disorder that affects about 5% of all couples.In up to 50% of women who have experienced RSA, the cause still remains unexplained, with genetic problem proposed as a main cause. X chromosome inactivation (XCI) is a physiological phenomenon in female mammals for 'dosage compensation' of X-linked genes with males. A normal female is mosaic, with about one-half of her somatic cells expressing the paternal derived X and the remainder of her cells using maternal X. In some situations, however, the inactivation is not random, resulting in a female having most or even all her somatic cells inactivating the same X chromosome from either paternal or maternal resource, which is known as skewed X-chromosome inactivation (SXCI).Evidence of an association between skewed X chromosome inactivation (SXCI) and idiopathic recurrent spontaneous abortion (RSA) is conflicting. This is a single-center observational case-control trial to determine whether there is higher incidence of skewed X chromosome inactivation(SXCI) in the recurrent miscarriage(RM) population compared with normal population, and verify the existing hypothesis of the possible genetic mechanisms underlying the association between SXCI and RM.

Inclusion criteria

• 1) regular menstrual cycles and normal level of E2, P, FSH, LH, T, RPL in the early follicular phase; 2) no history of gynecologic or other pelvic operations; 3) no history of hormone medicine application in the last 3 months; 4) no history of poison contact; 5) normal uterine and adnexal ultrasonography; 6) TORCH(-), chlamydia(-), mycoplasma(-), normal leucorrhoea routine, anti-phospholipid antibody (-), antinuclear antibody(-); 7) for the couple, no blood type incompatibility or ABO antibody IgG≤1：64 and normal blood chromosome analysis; 8) condoms are used for contraception.

Exclusion criteria

• 1) BMI<18.5 or >24.9; 2) hydrosalpinx without operation; endometriosis; polycystic ovary syndrome; adenomyosis; uterine leiomyomata(submucous myoma or non-submucous myoma which size was exceed 4cm and/or with the compressed endometrium);uterine cavity lesions(such as uterine malformation, intrauterine adhesions, the septate uterus, endometritis etc); 3) the former abortion is because of luteal phase defect without treatment; 4) FSH≥12IU/L or AMH<1.2ng/ml 5) thyroid dysfunction or increased CA125 level; 6) acute inflammation of genitourinary system or STD carriers; 7) unable to comply with the study procedures.