Association Between Glycemic Variability, HbA1c, and Large-for-Gestational-Age Neonates in Women With Type 1 Diabetes

Complex Management of Nephrotic Syndrome and Kidney Failure during Pregnancy in a Type 1 Diabetes Patient: A Challenging Case

Pregnancy with chronic kidney disease is challenging, and patients with diabetic nephropathy are at particular risk of a rapid kidney function decline during pregnancy. While indications for the management of pregnant patients with initial diabetic nephropathy are widely available in the literature, data on patients with severe nephrotic syndrome and kidney function impairment are lacking, and the decision on whether and when dialysis should be initiated is not univocal. We report a type 1 diabetes patient who started pregnancy with a severe nephrotic syndrome and shifted from CKD stage 3b to stage 5 during pregnancy. The management was complicated by a fetal heart malformation and by poorly controlled diabetes. The evidence for and against starting dialysis was carefully evaluated, and the choice of strict nephrological and obstetrical monitoring, nutritional management, and diuretic treatment made it possible to avoid dialysis in pregnancy, after ruling out pre-eclampsia. This experience enables examination of some open issues and contributes to the discussion of when to start dialysis in pregnancy.

Glycated albumin and continuous glucose monitoring metrics across pregnancy in women with pre-gestational diabetes

INTRODUCTION

Glycated albumin (GA), a biomarker reflecting short-term glycaemia, may be useful to assess glycaemic control in pregnancy. We examined the association between GA and continuous glucose monitoring (CGM) metrics across gestation.

METHODS

In this prospective cohort study including 40 women with pre-gestational diabetes, blood samples for analysis of GA and glycated haemoglobin A1c (HbA1c) were collected at pregnancy week 12, 20, 24, 28, 32 and 36. In the CGM-group (n = 19), CGM data were collected from first trimester until pregnancy week 36. Receiver operating characteristic (ROC) curves were used to assess the accuracy of GA and HbA1c to detect poor glycaemic control, using CGM metrics as the reference standard. This study was conducted at Stavanger University Hospital, Norway, in 2016-2018.

RESULTS

Glycaemic control improved across gestation with more time spent in target range, coinciding with decreased glycaemic variability and lower mean GA level. There was statistically significant correlation between GA and most CGM metrics. The area under the ROC curves (AUC) for detecting time in range <70% and time above range >25% for the pregnancy glucose target 63-140 mg/dl (3.5-7.8 mmol/L) were 0.78 and 0.82 for GA, whereas AUCs of 0.60 and 0.72 were found for HbA1c, respectively.

CONCLUSIONS

Higher GA levels were associated with less time spent in target range, more time spent in the above range area and increased glycaemic variability. GA was more accurate than HbA1c to detect time above range >25% and time in range <70%.

Glycemic Variability in Type 1 Diabetes Mellitus Pregnancies—Novel Parameters in Predicting Large-for-Gestational-Age Neonates: A Prospective Cohort Study

Pregnancies with type 1 diabetes mellitus (T1DM) have a high incidence of large-for-gestational-age neonates (LGA) despite optimal glycemic control. In recent years, glycemic variability (GV) has emerged as a possible risk factor for LGA, but the results of the conducted studies are unclear. This study analyzed the association between GV and LGA development in pregnancies with T1DM. This was a prospective cohort study of patients with T1DM who used continuous glucose monitoring (CGM) during pregnancy. Patients were followed from the first trimester to birth. GV parameters were calculated for every trimester using the EasyGV calculator. The main outcomes were LGA or no-LGA. Logistic regression analysis was used to assess the association between GV parameters and LGA. In total, 66 patients were included. The incidence of LGA was 36%. The analysis extracted several GV parameters that were significantly associated with the risk of LGA. The J-index was the only significant parameter in every trimester of pregnancy (odds ratios with confidence intervals were 1.33 (1.02, 1.73), 3.18 (1.12, 9.07), and 1.37 (1.03, 1.82), respectively. Increased GV is a risk factor for development of LGA. The J-index is a possible novel GV parameter that may be assessed in all three trimesters of pregnancy together with glycated hemoglobin and time-in-range.

Relationship Between Time-in-Range, HbA1c, and the Glucose Management Indicator in Pregnancies Complicated by Type 1 Diabetes

Objective: We aimed to evaluate relationships between time-in-range (TIR 63-140 mg/dL), glycated hemoglobin A1c (HbA1c) level, and the glucose management indicator (GMI) in pregnant women with type 1 diabetes. Research Design and Methods: Continuous glucose monitoring (CGM) data from 27 women with type 1 diabetes were collected prospectively throughout pregnancy. Up to 90-days of CGM data were correlated with point-of-care HbA1c levels measured in the clinic at each trimester. GMI levels were calculated using a published regression formula. Liner models were used to compare TIR, HbA1c, and GMI by each trimester. Results: There was a significant negative correlation between TIR and HbA1c; each 10% increase in TIR was associated with a 0.3% reduction in HbA1c. The correlation between TIR and HbA1c was stronger (r = -0.8) during the second and third trimesters than during the first trimester (r = -0.4). There was good correlation between TIR and GMI during each trimester (r = 0.9 for each trimester). The relationship between GMI and HbA1c especially during second (r = 0.8) and third trimesters (r = 0.8) was strong. Conclusion: In the first trimester, the correlation between HbA1c level and TIR was relatively small, while that of TIR and GMI was very strong, thus GMI may better reflect glycemic control than HbA1c in early pregnancy. Each 10% increase in TIR was associated with a 0.3% reduction in HbA1c throughout pregnancy, which was lower than other published studies in nonpregnant populations reporting a 0.5%-0.8% reduction in HbA1c. Further studies are needed to understand the relationship between TIR and GMI and how GMI may affect maternal and fetal complications. Clinical Trial Registration number: NCT02556554.

Third trimester HbA1c and the association with large-for-gestational-age neonates in women with gestational diabetes

Objective

To evaluate the association between HbA1c levels measured in the third trimester and the risk for large for gestational age (LGA) in neonates of mothers affected by gestational diabetes mellitus (GDM). Secondarily, we aimed to identify an ideal cut-off for increased risk of LGA amongst pregnant women with GDM.

Methods

Observational retrospective review of singleton pregnant women with GDM evaluated in a diabetes and pregnancy clinic of a tertiary and academic hospital. From January/2011 to December/2017, 1,085 pregnant women underwent evaluation due to GDM, of which 665 had an HbA1c test in the third trimester. A logistic regression model was performed to evaluate predictors of LGA. A receiver-operating-characteristic (ROC) curve was used to evaluate the predictive ability of third trimester HbA1c for LGA identification.

Results

A total of 1,085 singleton pregnant women were evaluated during the study period, with a mean age of 32.9 ± 5.3 years. In the multivariate analysis, OGTT at 0 minutes (OR: 1.040; CI 95% 1.006-1.076, p = 0.022) and third trimester HbA1c (OR: 4.680; CI 95% 1.210-18.107, p = 0.025) were associated with LGA newborns. Using a ROC curve to evaluate the predictive ability of third trimester HbA1c for LGA identification, the optimal HbA1c cut-off point was 5.4% where the sensitivity was 77.4% and the specificity was 71.7% (AUC 0.782; p < 0.001).

Conclusion

Few studies in the Mediterranean population have evaluated the role of HbA1c in predicting neonatal complications in women with GDM. A third trimester HbA1c > 5.4% was found to have good sensitivity and specificity for identifying the risk of LGA.

Exploratory Analysis of Glycemic Control and Variability Over Gestation Among Pregnant Women with Type 1 Diabetes

In exploratory analyses, we evaluated glycemic variability (GV) and gestational outcomes in pregnant women (n = 28) with type 1 diabetes (T1D). Gestational age at delivery was higher for women with lower glycemic measures, including estimated HbA1c (eHbA1c) (0.14% decrease in HbA1c per 1-week greater gestational age, P = 0.0035), mean sensor glucose (-3.9 mg/dL P = 0.0039), time spent >140 mg/dL (-3.1%, P = 0.0029), and higher time in range (TIR) of 63-140 mg/dL (3.2%, P = 0.0029). Third trimester measured HbA1c was significantly associated with gestational age at delivery (P = 0.0081). Preeclampsia was associated with less TIR in first (50.5% vs. 69.9%, P = 0.0034) and second trimesters (47.1% vs. 66.7%, P = 0.0025), but not with measured HbA1c. There were significant differences in other markers of GV (continuous overall net glycemic action, high blood glucose index, J-index, mean amplitude of glycemic excursions) with infant birth weight and gestational age at delivery. Thus, multiple markers of glycemia and GV were associated with gestational health outcomes in T1D pregnancies in this pilot study. Clinical Trial Registration number: NCT02556554.

Continuous Glucose Monitoring Time-in-Range and HbA1c Targets in Pregnant Women with Type 1 Diabetes

The CONCEPTT trial compared real-time Continuous Glucose Monitoring (RT-CGM) to capillary glucose monitoring in pregnant women with type 1 diabetes. We analyzed CGM and glycated hemoglobin (HbA_1c) measures in first (n = 221), second (n = 197), and third (n = 172) trimesters, aiming to examine target glucose attainment and associations with pregnancy outcomes. CGM targets were Time-in-range (TIR) > 70%, Time-above-range (TAR) <25%, and Time-below-range (TBR) < 4%, and HbA_1c targets < 6.5% (National Institute for Health and Care Excellence [NICE]) and HbA_1c < 6.0% in second and third trimesters (American Diabetes Association [ADA]). TIR/TAR/TBR targets were achieved by 7.7/14.5/30.3% participants in first, 10.2/14.2/52.8% in second, and 35.5/37.2/52.9% in third trimesters. CGM target attainment was low but increased during pregnancy and with RT-CGM use. In the adjusted analyses, achieving TBR target was associated with a higher risk of pre-eclampsia and neonatal hypoglycemia. ADA HbA_1c target attainment was low and unchanged during pregnancy (23.5/27.9/23.8%) but increased with RT-CGM use. In the adjusted analyses, HbA_1c target attainment was associated with a lower risk of preterm birth, large-for-gestational age and neonatal hypoglycemia. We conclude that CONCEPTT trial participants had a low rate of CGM and of HbA_1c target attainment. Attainment of CGM and NICE HbA_1c targets increased throughout gestation and all targets (both NICE/ADA HbA_1c and CGM) were more likely to be achieved by RT-CGM users, at 34 weeks' gestation. ADA HbA_1c target achievement was independently associated with better perinatal outcomes, while the independent association of TBR target achievement with increased risk warrants further study. ClinicalTrials.gov Registration Identifier NCT01788527.

Pregnancy outcomes and maternal characteristics in women with pregestational and gestational diabetes: a retrospective study on 206,917 singleton live births

AIMS

To examine risk of adverse pregnancy outcomes, mothers' characteristics and incidence rate over time of pregestational type 1 (T1D), type 2 (T2D) or gestational diabetes (GDM).

METHODS

The study included all singleton live births born from women aged 15-45 year, in Tuscany, Italy from 2010 to 2018. Pregnancy outcomes were retrieved by certificates of care at delivery compiled by midwives. Pregestational diabetes and GDM were identified by regional administrative databases. Time course of pregestational diabetes and GDM across last decade was assessed by Poisson analysis. Logistic regression analysis was used to calculate adjusted odds ratios (OR; 95% CI) for maternal characteristics or neonatal outcomes.

RESULTS

Among 206,917 singleton live births, GDM was diagnosed in 21,613 pregnancies (10.46%) and pregestational diabetes in 979, being T2D more prevalent than T1D (606; 0.29% vs. 373; 0.18%). Pregestational T2D incidence progressively decreased over last decade, T1D remained stable while GDM progressively rose. Pre-pregnancy obesity, preterm deliveries or cesarean sections were common characteristics of pregestational diabetes and GDM. Risk of neonatal distress and neonatal malformations was higher in pregestational T1D. Risk of prior spontaneous abortions was higher in GDM and in pregestational T2D (OR: 4.19; 3.30-5.33), mostly treated with metformin. Risk of neonatal macrosomia was increased only in pregestational diabetes.

CONCLUSIONS

In our population, pregestational T2D was more prevalent than T1D. Neonatal complications were mostly associated with pregestational T1D. Increased risk of previous spontaneous abortions was the hallmark of pregestational T2D. GDM, even if sharing adverse outcomes with pregestational T2D, was unrelated to rise in risk of neonatal macrosomia.

A Review on Research Progress in the Application of Glycosylated Hemoglobin and Glycated Albumin in the Screening and Monitoring of Gestational Diabetes

Glycosylated hemoglobin (HbA1C) and glycated albumin (GA) can be used for blood glucose management of a person with diabetes as a result of their convenience and stability. However, there is no corresponding standard for the application of glycosylated hemoglobin and glycosylated albumin in gestational diabetes mellitus (GDM). In this review, we summarize the published research and discuss three aspects of the significance of HBA1C and GA in GDM patients: screening of gestational diabetes mellitus, blood glucose monitoring and the relationship with pregnancy outcome. At present, studies suggest that HBA1C can be used as a screening indicator for pregnant women, but it cannot completely replace OGTT. HbA1C and GA can be used for blood glucose management in patients with GDM to reduce the incidence of GDM complications. However, the application of HBA1C and GA in GDM still needs more research and clinical practice support.

Evaluation of Glycaemic Control, Glucose Variability and Hypoglycaemia on Long-Term Continuous Subcutaneous Infusion vs. Multiple Daily Injections: Observational Study in Pregnancies With Pre-Existing Type 1 Diabetes

INTRODUCTION

We evaluated the effectiveness of long-term continuous subcutaneous insulin infusion (CSII) compared with multiple daily insulin (MDI) injections for glycaemic control and variability, hypoglycaemic episodes and maternal/neonatal outcomes in pregnant women with pre-existing type 1 diabetes (pT1D).

METHODS

Our observational cohort study included 128 consecutive pregnant women with pT1D, who were treated from 1 January 2010 to 31 December 2017. Of 128 participants, 48 were on CSII and 80 were on MDI. Glycaemic control was determined by glycated haemoglobin (HbA1c) (captured in preconception and each trimester of pregnancy). Glucose variability (GV) was expressed as the coefficient of variation (CV) [calculated from self-monitoring of blood glucose (SMBG) values], and hypoglycaemia was defined as glucose values < 3.9 mmol/l. The data on maternal and neonatal outcomes were collected from obstetrical records.

RESULTS

Duration of the treatment was 8.8 ± 5.3 years in the CSII and 12.6 ± 8.0 years in the MDI group. The CSII lowered HbA1c in preconception (7.1 ± 0.1 vs. 7.9 ± 0.2%, p = 0.03) and the first (6.9 ± 0.1 vs. 7.7 ± 0.2%, p = 0.02), second (6.6 ± 0.1 vs. 7.2 ± 0.1%, p = 0.003) and third (6.5 ± 0.1 vs. 6.8 ± 0.1%, p = 0.02) trimesters significantly better than MDI. Significantly lower CV was observed only for fasting glycaemia in the first trimester (17.1 vs 28.4%, p < 0.001) in favour of CSII. Moreover, the CSII group had significantly lower mean hypoglycaemic episodes/week/patient only during the first trimester (2.0 ± 1.7 vs 4.8 ± 1.5, p < 0.01). In early pregnancy, the majority of women on CSII had less hypoglycaemia than on MDI (0-3: 79.1 vs. 29.1%; 4-6: 18.8 vs. 65.8%; ≥ 7: 2.1 vs. 5.1%, p < 0.01, respectively). We found no difference in the incidence of adverse maternal/neonatal outcomes.

CONCLUSIONS

Treatment with CSII resulted in a favourable reduction of HbA1c in the preconception period and each trimester in pregnancy. Moreover, long-term CSII treatment demonstrated more stable metabolic control with less GV of fasting glycaemia and fewer hypoglyacemic episodes only during early pregnancy.

Prepregnancy care in women with type 1 diabetes improves HbA1c and glucose variability without worsening hypoglycaemia time and awareness: Glycaemic variability during prepregnancy care

AIMS

To evaluate the impact of a prepregnancy care (PPC) programme, beyond HbA_1c, on hypoglycaemia awareness and glycaemic variability (GV).

METHODS

Prospective pilot study. We selected women with Type 1 diabetes who initiated a PPC programme with normal hypoglycaemia awareness (n = 24). Hypoglycaemia awareness, hypoglycaemic events and GV derived from masked-continuous glucose monitoring were evaluated in the first visit and within 2 weeks after pregnancy confirmation.

RESULTS

The duration was 16.5 ± 13.0 months. HbA_1c significantly decreased (-0.8 ± 0.7; p < 0.001). The Clarke score increased (0[0-1] vs. 1[0-2] points, p = 0.164), 2 out of 24 were reclassified as having impaired awareness of hypoglycaemia and 2 presented severe hypoglycaemia. GV decreased: standard deviation (p = 0.008), coefficient of variation (p = 0.021), mean amplitude of glycaemic excursions (p = 0.007), average daily risk range (p < 0.001), J-index (p = 0.010), high blood glucose index (HBGI) (p = 0.004), continuous overall net glycaemic action (CONGA) (p = 0.018), mean of daily differences (p = 0.045) and glycaemic risk assessment diabetes equation (p = 0.012). Final HbA_1c was associated with baseline J-index, CONGA and HBGI (β = 0.535, β = 0.466, β = 0.534, respectively; p < 0.05).

CONCLUSIONS

A PPC programme improved HbA_1c as well as GV with no significant impact on hypoglycaemia awareness. Moreover, GV could help to identify women less likely to achieve glycaemic targets. Larger studies are needed to confirm these results.

Continuous glucose monitoring in pregnant women with type 1 diabetes: an observational cohort study of 186 pregnancies

AIMS/HYPOTHESIS

The aim of this study was to analyse patterns of continuous glucose monitoring (CGM) data for associations with large for gestational age (LGA) infants and an adverse neonatal composite outcome (NCO) in pregnancies in women with type 1 diabetes.

METHODS

This was an observational cohort study of 186 pregnant women with type 1 diabetes in Sweden. The interstitial glucose readings from 92 real-time (rt) CGM and 94 intermittently viewed (i) CGM devices were used to calculate mean glucose, SD, CV%, time spent in target range (3.5-7.8 mmol/l), mean amplitude of glucose excursions and also high and low blood glucose indices (HBGI and LBGI, respectively). Electronic records provided information on maternal demographics and neonatal outcomes. Associations between CGM indices and neonatal outcomes were analysed by stepwise logistic regression analysis adjusted for confounders.

RESULTS

The number of infants born LGA was similar in rtCGM and iCGM users (52% vs 53%). In the combined group, elevated mean glucose levels in the second and the third trimester were significantly associated with LGA (OR 1.53, 95% CI 1.12, 2.08, and OR 1.57, 95% CI 1.12, 2.19, respectively). Furthermore, a high percentage of time in target in the second and the third trimester was associated with lower risk of LGA (OR 0.96, 95% CI 0.94, 0.99 and OR 0.97, 95% CI 0.95, 1.00, respectively). The same associations were found for mean glucose and for time in target and the risk of NCO in all trimesters. SD was significantly associated with LGA in the second trimester and with NCO in the third trimester. Glucose patterns did not differ between rtCGM and iCGM users except that rtCGM users had lower LBGI and spent less time below target.

CONCLUSIONS/INTERPRETATION

Higher mean glucose levels, higher SD and less time in target range were associated with increased risk of LGA and NCO. Despite the use of CGM throughout pregnancy, the day-to-day glucose control was not optimal and the incidence of LGA remained high.

Large-for-Gestational-Age Neonates in Type 1 Diabetes and Pregnancy: Contribution of Factors Beyond Hyperglycemia

Despite significant reductions in serious adverse perinatal outcomes for women with type 1 diabetes in pregnancy, the opposite effect has been observed for fetal overgrowth and associated complications, such as neonatal hypoglycemia, shoulder dystocia, and admission to the neonatal intensive care unit. In addition, infants born large for gestational age (LGA) have an increased lifetime risk of obesity, diabetes, and chronic disease. Although exposure to hyperglycemia plays an important role, women who seemingly achieve adequate glycemic control in pregnancy continue to experience a greater risk of excess fetal growth, leading to LGA neonates and macrosomia. We review potential contributors to excess fetal growth in pregnancies complicated by type 1 diabetes. In addition to hyperglycemia, we explore the role of glycemic variability, prepregnancy overweight and obesity, gestational weight gain, and maternal lipid levels. Greater understanding of the stimuli that drive excess fetal growth could lead to targeted management strategies in pregnant women with type 1 diabetes, potentially reducing the incidence of LGA neonates and the inherent risk of acute and long-term complications.

Continuous Glucose Monitoring, Glycemic Variability, and Excessive Fetal Growth in Pregnancies Complicated by Type 1 Diabetes

BACKGROUND

To examine trimester-specific associations among glycemic variability, fetal growth, and birthweight in pregnancies with type 1 diabetes mellitus (Type 1 DM).

METHODS

In this retrospective cohort study of 41 pregnant women with Type 1 DM, we used continuous glucose monitoring (CGM) data to calculate glycemic variability (coefficient of variation of glucose) over a 7-day interval in each trimester. Clinical data, including fetal biometry, birthweight, and perinatal complications, were extracted from medical records.

RESULTS

Women maintained good glycemic control during pregnancy, with mean HbA1c in the first, second, and third trimester 6.5%, 6.1%, and 6.4%, respectively. Sixty-three percent of infants were large for gestational age (LGA). Estimated fetal weight percentile (EFW%ile) and abdominal circumference percentile (AC%ile) increased during pregnancy, consistent with accelerated prenatal growth. Correlations between trimester-specific glycemic variability and EFW, AC, and birthweight were not statistically significant. After maternal age adjustment, glycemic variability was not associated with birthweight for any trimester (adj. β for first trimester: -38.46, 95% CI: -98.58 to 21.66; adj. β for second trimester: -12.20, 95% CI: -51.47 to 27.06; adj. β for third trimester: -26.26, 95% CI: -79.52 to 27.00).

CONCLUSIONS

The occurrence of LGA remains very high in contemporary U.S. women with Type 1 DM, despite the use of CGM and overall good glycemic control. Neither HbA1c nor glycemic variability predicted fetal overgrowth or birthweight. Since LGA is a key driver of maternal and newborn complications in pregnancies with Type 1 DM, our data emphasize the importance of investigating both glucose-dependent and glucose-independent underlying mechanisms.

The Emerging Role of Biomarkers in the Diagnosis of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is a common complication of pregnancy; its rising incidence is a result of increased maternal obesity and older maternal age together with altered diagnostic criteria identifying a greater proportion of pregnant women with GDM. Its consequences are far-reaching, associated with poorer maternal and neonatal outcomes compared to non-GDM pregnancies, and GDM has implications for metabolic health in both mother and offspring. Objective markers to identify women at high risk for the development of GDM are useful to target therapy and potentially prevent its development. Established clinical risk factors for GDM include overweight/obesity, age, ethnicity, and family history of diabetes, though they lack specificity for its development. The addition of biomarkers to predictive models of GDM may improve the ability to identify women at risk of GDM prior to its development. These biomarkers reflect the pathophysiologic mechanisms of GDM involving insulin resistance, chronic inflammation, and altered placental function. In addition, the role of epigenetic changes in GDM pathogenesis highlights the complex interplay between genetic and environmental factors, potentially offering further refinement of the prediction of GDM risk. In this review, we will discuss the clinical challenges associated with the diagnosis of GDM and its current pathophysiologic basis, giving rise to potential biomarkers that may aid in its identification. While not yet validated for clinical use, we explore the possible clinical role of biomarkers in the future. We also explore novel diagnostic tools, including high throughput methodologies, that may have potential future application in the identification of women with GDM.

Controversies and Advances in Gestational Diabetes-An Update in the Era of Continuous Glucose Monitoring

Diabetes in pregnancy, both preexisting type 1 or type 2 and gestational diabetes, is a highly prevalent condition, which has a great impact on maternal and fetal health, with short and long-term implications. Gestational Diabetes Mellitus (GDM) is a condition triggered by metabolic adaptation, which occurs during the second half of pregnancy. There is still a lot of controversy about GDM, from classification and diagnosis to treatment. Recently, there have been some advances in the field as well as recommendations from international societies, such as how to distinguish previous diabetes, even if first recognized during pregnancy, and newer diagnostic criteria, based on pregnancy outcomes, instead of maternal risk of future diabetes. These new recommendations will lead to a higher prevalence of GDM, and important issues are yet to be resolved, such as the cost-utility of this increase in diagnoses as well as the determinants for poor outcomes. The aim of this review is to discuss the advances in diagnosis and classification of GDM, as well as their implications in the field, the issue of hyperglycemia in early pregnancy and the role of hemoglobin A1c (HbA1c) during pregnancy. We have looked into the determinants of the poor outcomes predicted by the diagnosis by way of oral glucose tolerance tests, highlighting the relevance of continuous glucose monitoring tools, as well as other possible pathogenetic factors related to poor pregnancy outcomes.