Establishing trimester- and ethnic group-related reference ranges for fructosamine and HbA1c in non-diabetic pregnant women

Early to mid-pregnancy HbA1c levels and its association with adverse pregnancy outcomes in three low middle-income countries in Asia and Sub-Saharan Africa

BACKGROUND

Hyperglycemia during pregnancy leads to adverse maternal and fetal outcomes. Thus, strict monitoring of blood glucose levels is warranted. This study aims to determine the association of early to mid-pregnancy HbA1c levels with the development of pregnancy complications in women from three countries in South Asia and Sub-Saharan Africa.

METHODS

We performed a secondary analysis of the AMANHI (Alliance for Maternal and Newborn Health Improvement) cohort, which enrolled 10,001 pregnant women between May 2014 and June 2018 across Sylhet-Bangladesh, Karachi-Pakistan, and Pemba Island-Tanzania. HbA1c assays were performed at enrollment (8 to < 20 gestational weeks), and epidemiological data were collected during 2-3 monthly household visits. The women were followed-up till the postpartum period to determine the pregnancy outcomes. Multivariable logistic regression models assessed the association between elevated HbA1c levels and adverse events while controlling for potential confounders.

RESULTS

A total of 9,510 pregnant women were included in the analysis. The mean HbA1c level at enrollment was found to be the highest in Bangladesh (5.31 ± 0.37), followed by Tanzania (5.22 ± 0.49) and then Pakistan (5.07 ± 0.58). We report 339 stillbirths and 9,039 live births. Among the live births were 892 preterm births, 892 deliveries via cesarean section, and 532 LGA babies. In the multivariate pooled analysis, maternal HbA1c levels of ≥ 6.5 were associated with increased risks of stillbirths (aRR = 6.3, 95% CI = 3.4,11.6); preterm births (aRR = 3.5, 95% CI = 1.8-6.7); and Large for Gestational Age (aRR = 5.5, 95% CI = 2.9-10.6).

CONCLUSION

Maternal HbA1c level is an independent risk factor for predicting adverse pregnancy outcomes such as stillbirth, preterm birth, and LGA among women in South Asia and Sub-Saharan Africa. These groups may benefit from early interventional strategies.

Establishing Trimester-Specific Haemoglobin A1c Reference Intervals in Pregnant Women: A retrospective study of healthy South Asian women with normal pregnancy outcomes

Objectives

This study aimed to define trimester-specific haemoglobin A1c (HbA1c) reference intervals in healthy, pregnant South Asian women.

Methods

This retrospective study was conducted at St. Stephen's Hospital, Delhi, India, between January 2011 and December 2016. Healthy pregnant women were compared to a control group of healthy non-pregnant women. Pregnant participants had term deliveries of babies with appropriate gestational weights. The HbA1c levels were calculated in terms of non-parametric 2.5 and 97.5 percentiles for women in first (T1), second (T2) and third (T3) trimester groups. Statistical tests were used to obtain the normal HbA1c reference values and were considered significant when P <0.05.

Results

This study included a total of 1,357 healthy pregnant women and a control group of 67 healthy, non-pregnant women. Pregnant women had a median HbA1c of 4.8% (4-5.5%) or 32 mmol/mol (20-39 mmol/mol); non-pregnant women had a median HbA1c of 5.1% (4-5.7%) or 29 mmol/mol (20-37 mmol/mol; P <0.001). The HbA1c levels for the T1, T2 and T3 groups were 4.9% (4.1-5.5%) or 30 mmol/mol (21-37 mmol/mol), 4.8% (4.5-5.3%) or 29 mmol/mol (20-34 mmol/mol) and 4.8% (3.9-5.6%) or 29 mmol/mol (19-38 mmol/mol), respectively. The HbA1c values were significant when comparing T1 versus T2 (P <0.001), T1 versus T3 (P = 0.002) and T1 versus the non-pregnant group (P = 0.001). However, T2 versus T3 was not significant (P = 0.111).

Conclusion

Compared to non-pregnant women, HbA1c levels were lower in pregnant women, despite women in the T2 and T3 groups having a higher body mass index than the women in the T1 and non-pregnant groups. Further research is recommended to understand the factors responsible and validate these findings.

Early pregnancy triglycerides and not fructosamine are associated with birth weight (with foetal sexual dimorphism)

BACKGROUND

We evaluated whether maternal triglycerides (TGs) or fructosamine (measured in early pregnancy) predominantly contribute to birth weight (BW), in a foetal sexual dimorphism.

METHODS

Analysis of data from the Amsterdam Born Children and their Development cohort study (total n = 3514). Maternal nonfasting TGs and fructosamine were determined in early gestation (median 13 weeks). Multivariable linear regression analysis was used to determine whether maternal TGs or fructosamine was associated with BW-small for gestational age (SGA)-large for gestational age (LGA) and whether it was sex-dependent.

RESULTS

With each 1 mmol/L increase in TGs, BW increased significantly by 81.7 g. This increase was larger with boys (107.3 g; 95% CI 66-148) than girls (60.5 g; 95% CI 23.6-97.4). No association was found with fructosamine. When including different covariates (gestational age at blood sampling, total duration of pregnancy, maternal height, age, parity, ethnicity, educational level, smoking, alcohol, and pre-pregnancy BMI), 29% of the variance in BW can be explained. Adding fructosamine to this model gave no added value in predicting BW, in contrast to adding TGs (R² raised from 0.292 to 0.299, p < .001). The odds of a newborn LGA with higher maternal TG were increased (OR 1.6, 95% CI 1.3-2.0), in contrast to fructosamine.

CONCLUSIONS

Maternal TGs were more dominant (compared to fructosamine) in its association with BW (measured in early physiological pregnancy) and more prominently present when carrying a male foetus. These remarkable observations warrant more future research, especially in obese patients at risk for gestational diabetes.

Relationship of anthropometric measurements with glycated hemoglobin and 1-h blood glucose after 50 g glucose challenge test in pregnant women: A longitudinal cohort study in Southern Thailand

AIMS

To assess correlations of anthropometric measurements with glycated hemoglobin (HbA1c) and 1-h blood glucose after a 50 g glucose challenge test during the first and late second trimesters and explore their relationships of anthropometric measurements with neonatal birth weight.

METHODS

A longitudinal study was conducted among pregnant Thai women with gestational age ≤14 weeks. Anthropometric measurements, using body mass index, body compositions, and circumferences, and skinfold thickness, were measured at four-time points: ≤14, 18-22, 24-28, and 30-34 weeks of gestation. HbA1c and 1-h blood glucose were examined at ≤14 and 24-28 weeks. Neonatal birth weight was recorded.

RESULTS

Of 312 women, HbA1c was more correlated with anthropometric measurements during pregnancy than 1-h blood glucose. At 24-28 weeks, women with high/very high body fat percentage were more likely to have higher HbA1c. Women with high subscapular skinfold thickness were more likely to have higher 1-h blood glucose at ≤14 and 24-28 weeks. High hip circumference significantly increased neonatal birth weights.

CONCLUSION

Anthropometric measurements were longitudinally correlated with HbA1c and 1-h blood glucose, higher in the late second than first trimesters, as well as neonatal birth weight. The mechanisms to explain the relationship of different anthropometric measurements are required to be further studied.

Performance of early pregnancy HbA1c for predicting gestational diabetes mellitus and adverse pregnancy outcomes in obese European women

AIMS

To investigate the performance of early pregnancy HbA_1c for predicting gestational diabetes mellitus (GDM) and adverse pregnancy outcomes in obese women.

METHODS

Post hoc analysis using data from the Vitamin D And Lifestyle Intervention for GDM prevention trials conducted across 9 European countries (2012-2014). Pregnant women (BMI ≥ 29 kg/m²) underwent a baseline HbA_1c and oral glucose tolerance tests at < 20 weeks, 24-28 weeks, and 35-37 weeks. Women with GDM were referred for treatment.

RESULTS

Among the 869 women tested, the prevalence of GDM was 25.9% before 20 weeks, with a further 8.6% at 24-28 weeks. The areas under the curves for HbA_1c at the two time points were 0.55 (0.50-0.59) and 0.54 (0.47-0.61), respectively. An early HbA_1c ≥ 5.7% (39 mmol/mol) (N = 111) showed low sensitivity (18.2%) with 89.1% specificity for GDM before 20 weeks, at 24-28 weeks (sensitivity of 8.0% and specificity of 88.6% after excluding early GDM), and throughout gestation (sensitivity of 15.9% and specificity of 89.4%). The ≥ 5.7% (39 mmol/mol) threshold was significantly associated with concurrent GDM before 20 weeks (adjusted OR (aOR) 2.77(1.39-5.51)) and throughout gestation (aOR 1.72 (1.02-2.89)), but not adverse pregnancy outcomes.

CONCLUSIONS

Early pregnancy HbA_1c is of limited use for predicting either GDM or adverse outcomes in overweight/obese European women.

Association of first-trimester HbA1c levels with adverse pregnancy outcomes in different ethnic groups

AIM

To determine, in a multi-ethnic cohort, the association of first-trimester HbA1c levels with the development of pregnancy complications.

METHODS

A prospective study between April 2013-October 2016. Participants were stratified in five ethnic groups. Women had an HbA1c measurement added to their first antenatal bloods. Primary outcome was macrosomia and secondary outcomes included preeclampsia and large-for-gestational age (LGA). A multivariate logistic regression analysis was performed to adjust for potential confounders in determining the association between different HbA1c cut-off points and obstetric outcomes on each ethnic group.

RESULTS

1,882 pregnancies were included. Analysis was limited to the three main ethnic groups: Caucasian (54.3%), South-Central Asian (19%) and Latin-American (12.2%). There was no association between HbA1c levels and obstetric outcomes among Caucasians. In Latin-Americans, an HbA1c ≥ 5.8% (40 mmol/mol) was associated with higher risk of macrosomia, whereas an HbA1c ≥ 5.9% (41 mmol/mol) was associated with LGA. In South-Central Asian, an HbA1c ≥ 5.7% (39 mmol/mol) was associated with increased risk of macrosomia and a continuous graded relationship between HbA1c levels and preeclampsia and LGA was detected starting at HbA1c levels of 5.4% (36 mmol/mol).

CONCLUSION

First-trimester HbA1c levels perform as a suitable predictor of pregnancy complications in South-Central Asian and Latin-American women whereas in Caucasian no significant associations were found.

Impact of overt diabetes diagnosed in pregnancy in a multi-ethnic cohort in Spain

Overt diabetes (ODM) is defined as women without diabetes meeting the criteria for diabetes at the first antenatal visit. The risk of obstetric complications increases linearly with maternal glycemia and poorer maternal-fetal outcomes than in gestational diabetes (GDM) may be expected. Studies focusing on ODM pregnancy outcomes are lacking. We aimed to analyze maternal characteristics and pregnancy outcomes in ODM women compared with those with GDM. A retrospective cohort study of women giving birth between January 2010 and April 2013 was conducted. Participants with pre-gestational diabetes were excluded. All women underwent screening for GDM at the 24th-28th weeks of gestation or at the first prenatal visit in those with risk factors. HbA1c and a fasting glucose were measured in GDM women to rule out ODM. Of the 5,633 women included, 572 (10%) were diagnosed with GDM and 50 (0.88%) with ODM. Almost 95% of ODM women were from ethnic minorities. After adjustment for confounding factors, ODM women showed increased rates of premature birth (23.1% vs. 6.7%, p < .001), emergent cesarean section (41.0% vs. 19.5%, p = .049), preeclampsia (22% vs. 3.7%, p < .001) and large-for-gestational-age babies (40.0% vs. 14.8%, p = .008) compared with GDM. In conclusion, ODM is associated with poorer obstetric outcomes than GDM and affects mainly women from ethnic minorities.

Changes in biochemical tests in pregnancy and their clinical significance

Interpretation of laboratory investigations relies on reference intervals. Physiological changes in pregnancy may result in significant changes in normal values for many biochemical assays, and as such results may be misinterpreted as abnormal or mask a pathological state. The aims of this review are as follows: 1. To review the major physiological changes in biochemical tests in normal pregnancy. 2. To outline where these physiological changes are important in interpreting laboratory investigations in pregnancy. 3. To document the most common causes of abnormalities in biochemical tests in pregnancy, as well as important pregnancy-specific causes.

Reference intervals for hemoglobin A1c (HbA1c) in healthy Mexican pregnant women: a cross-sectional study

BACKGROUND

The reference intervals for hemoglobin A1c (HbA1c) in pregnant Mexican women without diabetes are not well defined. The study aims to determine the reference intervals for HbA1c at each trimester in healthy Mexican pregnant women.

METHODS

This cross-sectional study included healthy Mexican pregnant women in trimester 1 (T1), 6-13.6 weeks of gestation (WG), trimester 2 (T2), 14-27 WG, and trimester 3 (T3), ≥27-36 WG, with a maternal age > 18 years, and pregestational body mass index (BMI) ranging between 18.5-24.9 kg/m2. Women with gestational diabetes mellitus, pregestational diabetes, anemia, a pregestational BMI < 18.5 or ≥ 25 kg/m2, and any hematologic, hepatic, immunological, renal, or cardiac disease were excluded. HbA1c was measured using high-performance liquid chromatography based on the National Glycohemoglobin Standardization Program-certified PDQ Primus guidelines. The HbA1c reference intervals were calculated in terms of the 2.5th to the 97.5th percentiles.

RESULTS

We analyzed the HbA1c values of 725 women (T1 n = 84, T2 n = 448, and T3 n = 193). The characteristics of the participants were expressed as mean ± standard deviation and included: maternal age (28.2 ± 6.7 years), pregestational weight (54.8 ± 5.9 Kg), pregestational BMI (22.2 ± 1.7 Kg/m2), and glucose values using a 75 g-2 h oral glucose tolerance test; fasting 4.5 ± 0.3 mmol/L (81.5 ± 5.5 mg/dL), 1 h 6.4 ± 1.5 mmol/L (115.3 ± 26.6 mg/dL), and 2 h 5.7 ± 1.1 mmol/L (103.5 ± 19.6 mg/dL). Reference intervals for HbA1c, expressed as median and 2.5th to 97.5th percentile for each trimester were: T1: 5.1 (4.5-5.6%), T2: 5.0 (4.4-5.5%), and T3: 5.1 (4.5-5.6%).

CONCLUSIONS

The reference range of HbA1C in healthy Mexican pregnant women during pregnancy was 4.4% to 5.6%. We suggest as upper limits of HbA1c value ≤5.6%, 5.5%, and 5.7% for T1, T2, and T3, respectively among Mexican pregnant women.

Glycosylated haemoglobin for screening and diagnosis of gestational diabetes mellitus

OBJECTIVES

The oral glucose tolerance test (OGTT) is a cumbersome test that is time consuming, labour intensive and often poorly tolerated by pregnant women. To date, glycosylated haemoglobin (HbA1c) is the most accepted measure of chronic glycaemia outside of pregnancy. HbA1c is an uncomplicated test, less time consuming, does not require any specific patient preparation and is considered straightforward compared with the OGTT. Therefore, we prospectively tested the utility of the HbA1c when used as a screening tool in pregnancy for gestational diabetes mellitus (GDM).

SETTINGS

Primary health care. Single tertiary referral centre, Tasmania, Australia.

PARTICIPANTS

A direct comparison between HbA1c levels and the OGTT results in pregnant women, tested concurrently at the 24-28 gestational week, was undertaken. A full profile of 480 pregnant women during the period from September 2012 to July 2014 was completed. Median and mean age of participants was 29 years (range 18-47 years).

INTERVENTIONS

A simultaneous prospective assessment of HbA1c versus standard OGTT in a cohort of consecutive pregnant women presenting to our institute was performed.

RESULTS

The number of women who had GDM according to OGTT criteria was 57, representing 11.9% of the evaluated 480 pregnant women. Using a cut-off value for HbA1c at 5.1% (32 mmol/mol) for detecting GDM showed sensitivity of 61% and specificity of 68% with negative predictive value (NPV) of 93%, versus sensitivity of 27% and specificity of 95% with NPV of 91% when using HbA1c cut-off value of 5.4% (36 mmol/mol).

CONCLUSIONS

Our results suggest that pregnant women with an HbA1c of≥5.4% (36 mmol/mol) should proceed with an OGTT. This may result in a significant reduction in the burden of testing on both patients and testing facility staff and resources. Further investigations are required to integrate and optimise the HbA1c as a single, non-fasting, screening tool for GDM.

TRIAL REGISTRATION NUMBER

ACTRN12611000739910.

Influence of iron metabolism indices on HbA1c in non-diabetic pregnant women with and without iron-deficiency anemia: effect of iron supplementation

AIMS

Condition that influence erythrocyte turnover also affect HbA1c. Although many forms of anemia are associated with lowering of HbA1c, iron-deficiency anemia (IDA) tends to increase HbA1c. In this study, we examined the relationship between HbA1c and erythrocyte indices in non-diabetic pregnancy and assessed the effect of iron supplementation on HbA1c.

MATERIALS AND METHODS

150 women were studied (30 non-diabetic), non-pregnant, non-anemic women in child bearing women with varying parity as controls (Gp 1); 30 non-diabetic, non-anemic pregnant women in first trimester of pregnancy (Gp 2a); 30 non-diabetic, non-anemic pregnant women in second trimester of pregnancy (Gp 2b); 30 non-diabetic, non-anemic pregnant women in third trimester of pregnancy (Gp 2c) and 30 non-diabetic pregnant women with IDA (Gp 2d). HbA1c, OGTT, erythrocyte indices and iron metabolic indices were determined in Gp 2d subjects not supplemented with iron and repeated these indices after 3 months of iron-supplementation.

RESULTS

The mean fasting and postprandial blood glucose levels (79.9±8.0mg/dl, 108.1±14.1mg/dl) in Gp 1 were found to be significantly lower in first trimester among Gp 2a (74.4±5.3mg/dl and 97.2±11.1mg/dl), in second trimester among Gp 2b (76.2±5.2mg/dl and 103.4±7.9mg/dl) followed by increase in IIIrd trimester among Gp 2c (82.3±5.7mg/dl and 112.5±8.5mg/dl) subjects. A significant difference in HbA1c was also observed among the groups (HbA1c 4.7±0.3% in Gp 1; 4.6±0.4% in Gp 2a; 4.5±0.3 in Gp 2b; 4.7±0.3 in Gp 2c). Among Gp 2d subjects, HbA1c was 5.2±0.3% and the level decreased after iron supplementation to 5.1±0.3%. Significant correlation between erythrocyte indices, iron metabolic indices and HbA1c was also observed.

CONCLUSION

We conclude that consideration should be given for performing glucose testing in patients with IDA to ascertain the reliability of HbA1c in the diagnosis of diabetes. HbA1c concentrations in diabetic patients with IDA should be interpreted with caution.

HbA1c in pregnancy

During pregnancy, the glucose levels vary according to the hormonal changes and the metabolic needs necessary to maintain fetal nutrition but strict glycemic control is essential to minimize the maternal and fetal morbidity and mortality of pregnancies complicated by diabetes. Although considered the "gold standard" for diagnosis, measurement of glucose in the blood is subject to several limitations, many of which are not widely appreciated. Measurement of A1c for diagnosis is appealing as with one number, a total, integrated view of glycemia over time is derived though it has some inherent limitations. Thus, supplementation with HbA1c, as is common outside pregnancy, seems appropriate. Before pregnancy, the target for metabolic control in women with diabetes is HbA1c values near the normal range. However, the upper normal range of HbA1c during normal pregnancy is only sparsely investigated with different methods though recently a number of papers have been published regarding the determination of reference ranges for HbA1c in pregnancy. These changes may have clinical implications for the assessment and management of glycemic control in diabetic pregnancy and calls for establishment of separate reference limits of HbA1c levels in different trimesters as compared to general population.

Is there a relationship between mean blood glucose and glycated hemoglobin?

Measurement of hemoglobin A1c (HbA1c) is considered the gold standard for monitoring chronic glycemia of diabetes patients. Hemoglobin A1c indicates an average of blood glucose levels over the past 3 months. Its close association with the risk for the development of long-term complications is well established. However, HbA1c does not inform patients about blood glucose values on a daily basis; therefore, frequent measurements of blood glucose levels are necessary for the day-to-day management of diabetes. Clinicians understand what HbA1c means and how it relates to glucose, but this is not the case with patients. Therefore, the translation of the HbA1c results into something more familiar to patients seemed a necessity. The scope of this article is to review the literature to search for enough scientific evidence to support the idea of a close relationship between HbA1c and mean blood glucose (MBG), and to justify the translation of HbA1c into something that reflects the MBG. Most studies confirm a close relationship between HbA1c and MBG, although different studies result in different linear equations. Factors affecting this relationship may limit the usefulness and applicability of a unique mathematical equation to all diabetes populations.

Reference intervals for hemoglobin A1c in pregnant women: data from an Italian multicenter study

BACKGROUND

The reference intervals for hemoglobin A1c (Hb A1c) in pregnant women without diabetes are not well defined, and few examples of reference intervals established by networks of different laboratories are available.

METHODS

Five Italian Diabetic Care Units were involved in the study. Data were collected from 445 pregnant women without diabetes, selected on the basis of glucose challenge test results, and from 384 nonpregnant control women. The Hb A1c measurements were performed with HPLC systems aligned to the Diabetes Control and Complications Trial. Plasma glucose measurements were also performed locally. Both Hb A1c and glucose measurements were harmonized by running appropriate external quality assessment schemes. The reference intervals were calculated in terms of nonparametric 2.5th to 97.5th percentiles with 0.90 confidence intervals.

RESULTS

The Hb A1c measurements were reproducible (CV = 2.0%) and accurate [mean (SE) difference from the target values, -0.10 (0.06)%]. Glucose measurements were also reproducible (mean CV = 3.2%) and accurate [difference from the target values, -0.01 (0.04) mmol/L]. To calculate common reference intervals, we merged the data collected in the different centers. The Hb A1c reference intervals were 4.0%-5.5% for pregnant nondiabetic women and 4.8%-6.2% for nonpregnant controls.

CONCLUSIONS

Healthy pregnant women have lower Hb A1c concentrations than nonpregnant women. The reference intervals for Hb A1c in pregnant women should therefore be lower than those currently in use.

Determination of a diabetes control and complications trial-aligned HbA(1c) reference range in pregnancy

A diabetes control and complications trial (DCCT)-aligned 95% inter-fractile reference range for glycated haemoglobin in non-diabetic pregnancy was determined as 4.1-5.9% (n=493; two-sided 90% confidence intervals around the lower and upper limits are 4.0-4.2% and 5.8-6.0%, respectively).