This is a propensity score matching study in Chinese women to investigate the effect of the FSL-CGM system on maternal and neonatal outcomes in pregnant women with GDM. At the end of follow-up, although most maternal outcomes were not significantly different between the two groups, the FBG before delivery in the FSL-CGM group was significantly lower than that in the SMBG group. With regard to neonatal outcomes, the incidence of neonatal hypoglycemia was significantly lower in the FSL-CGM group than in the SMBG group. Besides, the neonates in the FSL-CGM group were also less likely to develop neonatal jaundice and be transferred to the neonatal department compared with the SMBG group. In addition, the GWG in the FSL-CGM group was less than in the SMBG group only in the normal weight subgroup, while the GWG was not significantly different between the two groups in the overweight/obese subgroup.

GDM refers to the normal glucose metabolism before pregnancy and high blood sugar that occurs during pregnancy. It is a temporary diabetes induced by pregnancy and one of the most common complications of pregnancy [23]. The short-term effects of GDM on mothers and babies include an increased risk of maternal complications during pregnancy. In the long term, patients may be at increased risk of developing GDM again and developing type 2 diabetes in the future. It also increases the risk of developing metabolic disorders in the fetus [24,25,26]. There is evidence that good glycemic control can improve adverse pregnancy and neonatal outcomes, so the method and quality of glucose monitoring are crucial. [5]. Our research employs the FSL-CGM, which facilitates swift detection of blood sugar fluctuations and allows prompt adjustments through behavioral modifications or medical treatment. Therefore, this study primarily investigates whether a FSL-CGM offers improvements in pregnancy and neonatal outcomes compared to traditional methods.

Prior research has established the efficacy and safety of flash glucose monitoring systems in enhancing glycemic control and facilitating the stringent glucose management required during pregnancy [8]. As a result, the use of this system has been recommended to pregnant women as a means of mitigating the risk of diabetes-related complications. Typically, conventional continuous glucose monitoring (CGM) systems necessitate at least two daily calibrations to ensure a reliable correlation between interstitial and capillary glucose levels. In contrast, the FSL-CGM sensors eliminate the need for calibration altogether. This feature significantly reduces potential variations that may arise from errors in self-monitoring of blood glucose (SMBG) results used for calibration, improper timing of calibrations, missed calibrations, or the use of sensor glucose values instead of SMBG values for calibration [27,28,29]. In this context, it has been reported that compared with the conventional monitoring method, the use of the FSL-CGM in patients with type 1 diabetes can significantly reduce the risk of nocturnal hypoglycemia, and has better sensitivity in the detection of abnormal glycemic levels [18].

Regarding the maternal glycemic control in the FSL-CGM group, this study demonstrated that the mean LAGE, ADRR, GMI, and M-value had significantly improved from the first 6 days to the last 6 days during the study period. Although these data from the FSL-CGM system only represent a 2-week period, it suggests that there are significantly more opportunities to improve glycemic control in women with GDM. Considering that the FSL-CGM system not only displays the current glucose value and the last 8 hours of glucose data but also provides trend information on glycemia levels, it can be speculated that such detailed blood glucose information may make it more effective and efficient in guiding treatment decisions for this challenging population compared to standard SMBG. More importantly, it can be used as an educational and motivational tool to engage patients in GDM management. The visibility of continuous blood glucose information regarding fluctuations in glucose levels may empower pregnant women with GDM to adjust their lifestyle and eating habits. In fact, in the present study, we also found that the fasting blood glucose (FBG) before delivery was significantly lower in the FSL-CGM group compared to the SMBG group.

One of the important findings in the present study is that the neonatal blood glucose in the FSL-CGM group was significantly higher than that in the SMBG group and the incidence of neonatal hypoglycemia was significantly higher in the SMBG group than in the FSL-CGM group. Besides, the neonates in the FSL-CGM group were also less likely to develop neonatal jaundice and be transferred to the neonatal department compared with the SMBG group. Persistent neonatal hypoglycemia can cause permanent damage to the neonatal central nervous system, such as developmental delay, cerebral palsy, cognitive impairment, microcephaly, visual impairment, and intractable epilepsy [30, 31]. Such results further supported the FSL-CGM system used in pregnant women with GDM was better than conventional methods.

It was well known that excessive gestational weight gain also significantly increases the risk of adverse outcomes such as cesarean section, premature rupture of membranes, fetal distress, puerperal infection, macrosomia, neonatal hypoglycemia, neonatal jaundice, and can affect the mother in later life [22]. FSL-CGM provides continuous glucose data without the need for frequent fingerstick measurements, which can help improve glycemic control [32]. Therefore, FSL-CGM may contribute to better management of GWG. By providing real-time glucose data, FSL-CGM allows for more precise adjustments in diet and insulin therapy, which can help prevent excessive weight gain during pregnancy. Additionally, FSL-CGM can enhance patient engagement and adherence to treatment plans [10], which are crucial for managing GWG. This is particularly important in the context of GDM, where patient adherence to glucose monitoring and management strategies can significantly impact pregnancy outcomes. In the present study, we found that the women with GDM in the FSL-CGM group gained significantly less weight than those in the SMBG group. When the participants were further dichotomized as normal weight and overweight/obese at baseline, the GWG in the FSL-CGM group was less than in the SMBG group only in the normal weight subgroup, while the GWG was not significantly different between the two groups in the overweight/obese subgroup. These findings may be attributed to the fact that, for overweight or obese patients, physicians at our center require participation in nutrition clinics and enforce stricter adherence to dietary, lifestyle, and exercise interventions compared to patients with normal weight. This comprehensive, pregnancy-long management system likely contributed to effective weight control, resulting in no significant difference in GWG between the two groups. In contrast, for pregnant women with normal weight at baseline, those using the FSL-CGM system could immediately observe the impact of different foods on their glycemic levels, enabling them to adjust food choices and dietary intake appropriately to achieve suitable GWG during pregnancy.

This research acknowledges several limitations. First, the lack of blinding may have introduced the Hawthorne effect, as participants might have altered their behaviors related to weight gain, nutrition, and exercise. Second, the small sample size of the FSL-CGM group, coupled with the fact that this region is a medically advanced area in China with a relatively low incidence of perinatal complications, may have constrained the ability to achieve statistically significant findings. For example, this study’s incidence rates of shoulder dystocia and polyhydramnios were zero. Lastly, the study lacked follow-up data on neonates postpartum and did not assess the risk of developing type 2 diabetes after childbirth.