Gestational diabetes mellitus (GDM) is a common complication of pregnancy, and previous studies have shown that pregnant women with GDM have a higher risk of developing infectious diseases of the reproductive tract than healthy pregnant women, but relevant cohort studies are rare.

To investigate the variation characteristics of vaginal microbiota in pregnant women with GDM at different gestational weeks, to compare the differences of vaginal microbiota between GDM and non-GDM women, and to observe the effects of vaginal microbiota changes on pregnancy outcomes.

In this study, we used a consecutive sampling method to recruit pregnant women who established their records and regulated health care at Daxing Teaching Hospital of Capital Medical University from March 2022 to March 2023. They underwent 75 g oral glucose tolerance test (OGTT) at 24-28 weeks of gestation to diagnose GDM. The GDM group was matched 1∶1 with the non-GDM group using propensity score matching method (PSM). Sample of vaginal secretions were collected at 24-28 weeks (stage A), 32-35 weeks (stage B) and 37-40 weeks (stage C) for three vaginal microecological examination, respectively. Based on the results, participants were further divided into the GDM normal vaginal flora subgroup, GDM abnormal vaginal flora subgroup, non-GDM normal vaginal flora subgroup and non-GDM abnormal vaginal flora subgroup, and were followed up until 7 d after delivery to assess pregnancy outcome.

A total of 426 participants were initially enrolled in this study, and GDM occurred in 141 cases. After PSM mathing, the GDM and non-GDM groups were successfully matched in 122 pairs. In this study, because 9 women with GDM and 5 women without GDM had preterm birth (<37 weeks of gestation), 113 women with GDM and 117 women without GDM ended up in stage C. The proportion of the dominant vaginal flora of Lactobacillus was higher in stage A than in stage C. Moreover, the vaginal pH, the incidence of vaginal flora abnormalities, and the incidence of BV and VVC were lower than those in stage C (P<0.05). The proportion of dominant bacteria as Lactobacillus in the GDM group was higher than that in the non-GDM group, and the incidence of abnormal vaginal flora and VVC was lower than that in the non-GDM group in stage A (P<0.05). In contrast, the proportion of the dominant bacterium Lactobacillus was lower in the GDM group than in the non-GDM group, and the incidence of abnormal vaginal flora was higher than in the non-GDM in stage C (P<0.05). The incidence of adverse pregnancy outcomes was higher in the GDM abnormal vaginal flora subgroup (n=65) than in the GDM normal vaginal flora subgroup (n=57) (P<0.05). In more details, the risk of adverse pregnancy outcomes in the GDM abnormal vaginal flora group was 1.830 times higher than that in the GDM normal vaginal flora group (RR=1.830, 95%CI=1.293-2.590, P<0.001) .

Compared with non-GDM pregnant women, GDM pregnant women had a lower incidence of vaginal flora abnormalities at 24-28 weeks of gestation and an increased risk of vaginal flora abnormalities after 37 weeks of gestation. GDM pregnant women with abnormal flora have higher risk of adverse pregnancy outcomes, so we recommend enhanced testing and management of vaginal microecology during pregnancy.

妊娠期糖尿病（GDM）是妊娠期常见并发症，既往研究表明，GDM孕妇生殖道感染性疾病的患病风险较高，但相关队列研究少见。

了解GDM孕妇不同孕周阴道菌群变化特点，对比GDM孕妇与非GDM孕妇阴道菌群差异，观察阴道菌群异常对妊娠结局的不良影响。

本研究采用连续抽样法，选取2022年3月—2023年3月在首都医科大学大兴教学医院建立档案并规范保健的孕妇，在妊娠24~28周行75 g口服糖耐量试验（OGTT）检查，诊断是否为GDM。采用倾向得分匹配法（PSM）进行GDM组与非GDM组1∶1匹配，于妊娠24~28周（A阶段）、妊娠32~35周（B阶段）和妊娠37~40周（C阶段）分别采集阴道分泌物，进行3次阴道微生态检测，并进一步分为GDM阴道菌群正常组、GDM阴道菌群异常组、非GDM阴道菌群正常组及非GDM阴道菌群异常组，随访至分娩后7 d以评估妊娠结局。

本研究最初纳入426名参与者，141例发生GDM。经过PSM匹配，GDM组和非GDM组成功匹配122对，作为研究队列。本研究中有9例GDM孕妇和5例非GDM孕妇发生早产（妊娠<37周），故最终有113例GDM孕妇和117例非GDM孕妇进入C阶段。A阶段阴道菌群优势菌为乳杆菌所占比例高于C阶段，阴道pH值、阴道菌群异常发生率、细菌性阴道病（BV）及外阴阴道假丝酵母菌病（VVC）发生率均低于C阶段（P<0.05）。A阶段GDM组优势菌为乳杆菌所占比例高于非GDM组，阴道菌群异常和VVC发生率均低于非GDM组（P<0.05）。C阶段GDM组优势菌乳杆菌比例低于非GDM组，阴道菌群异常发生率高于非GDM组（P<0.05）。GDM阴道菌群异常组（n=65）不良妊娠结局发生率高于GDM阴道菌群正常组（n=57）（P<0.05）；GDM阴道菌群异常组不良妊娠结局的发生风险是GDM阴道菌群正常组的1.830倍（RR=1.830，95%CI=1.293~2.590，P<0.001）。

GDM孕妇在妊娠37~40周时，阴道菌群异常发生率高于妊娠24~28周。相比于非GDM孕妇，GDM孕妇在妊娠24~28周时阴道菌群异常发生率低，而在妊娠37周后，阴道菌群异常发生风险升高。妊娠期阴道菌群异常是发生不良妊娠结局的危险因素，建议加强妊娠期阴道微生态的检测与管理。