Antenatal haemoglobin A1c centiles: does one size fit all?

Hemoglobin A1c Trajectories During Pregnancy and Adverse Outcomes in Women With Type 2 Diabetes: A Danish National Population-Based Cohort Study

OBJECTIVE

To identify and characterize groups of pregnant women with type 2 diabetes with distinct hemoglobin A1c (HbA1c) trajectories across gestation and to examine the association with adverse obstetric and perinatal outcomes.

RESEARCH DESIGN AND METHODS

This was a retrospective Danish national cohort study including all singleton pregnancies in women with type 2 diabetes, giving birth to a liveborn infant, between 2004 and 2019. HbA1c trajectories were identified using latent class linear mixed-model analysis. Associations with adverse outcomes were examined with logistic regression models.

RESULTS

A total of 1,129 pregnancies were included. Three HbA1c trajectory groups were identified and named according to the glycemic control in early pregnancy (good, 59%; moderate, 32%; and poor, 9%). According to the model, all groups attained an estimated HbA1c <6.5% (48 mmol/mol) during pregnancy, with no differences between groups in the 3rd trimester. Women with poor glycemic control in early pregnancy had lower odds of having an infant with large-for-gestational-age (LGA) birth weight (adjusted odds ratio [aOR] 0.57, 95% CI 0.40-0.83), and higher odds of having an infant with small-for-gestational age (SGA) birth weight (aOR 2.49, 95% CI 2.00-3.10) and congenital malformation (CM) (aOR 4.60 95% CI 3.39-6.26) compared with women with good glycemic control. There was no evidence of a difference in odds of preeclampsia, preterm birth, and caesarean section between groups.

CONCLUSIONS

Women with poor glycemic control in early pregnancy have lower odds of having an infant with LGA birth weight, but higher odds of having an infant with SGA birth weight and CM.

Preconception hemoglobin A1c in healthy women is not associated with fecundability or pregnancy loss

Objective

To examine the relationship of preconception hemoglobin A1c, a marker of cumulative exposure to glucose over the preceding 2–3 months, with time to pregnancy, pregnancy loss, and live birth among fecund women without diagnosed diabetes or other medical diseases.

Design

A secondary analysis of a prospective cohort of women participating in the Effects of Aspirin in Gestation and Reproduction (EAGeR) trial.

Setting

Four US academic medical centers.

Patient(s)

A total of 1,194 healthy women aged 18–40 years with a history of one or two pregnancy losses attempting spontaneous conception were observed for up to six cycles while attempting pregnancy and throughout pregnancy if they conceived.

Intervention(s)

Not applicable.

Main Outcome Measure(s)

Time to pregnancy, human chorionic gonadotropin pregnancy, clinical pregnancy, pregnancy loss, and live birth.

Result(s)

Although increasing preconception A1c level was associated with reduced fecundability (fecundability odds ratio [FOR] per unit increase in A1c 0.74; 95% confidence interval [CI] 0.57, 0.96) in unadjusted models and models adjusted for age, race, smoking and treatment arm (FOR 0.79; 95% CI 0.60, 1.04), results were attenuated after further adjustment for body mass index (FOR 0.91; 95% CI 0.68, 1.21). Preconception A1c levels among women without diagnosed diabetes were not associated with live birth or pregnancy loss.

Conclusions(s)

Among healthy women without diagnosed diabetes, we observed no association of A1c with live birth or pregnancy loss. The association between A1c and fecundability was influenced by body mass index, a strong risk factor for both diabetes and infertility. These data support current recommendations that preconception A1c screening should be reserved for patients with risk factors for diabetes.

Clinical Trial Registration Number

ClinicalTrials.gov: NCT00467363.

Midwifery awareness of diabetes in pregnancy screening guidelines in Aotearoa New Zealand

OBJECTIVE

Effective and timely management of gestational diabetes mellitus (GDM) requires early detection. However, screening rates have been shown to be relatively low in New Zealand, despite the introduction of national screening guidelines in 2014 which indicate that all pregnant women should be screened. Thus, the aim of this study was to explore the awareness of the New Zealand Ministry of Health Diabetes in Pregnancy screening guidelines by New Zealand midwives.

DESIGN

A 24-question online survey based upon the New Zealand screening guidelines was distributed via New Zealand midwifery social media groups to explore the awareness of New Zealand midwives with regard to screening for diabetes in pregnancy. Free text comments were also allowed, these were broadly categorized and reviewed.

PARTICIPANTS

174 registered midwives in Aotearoa New Zealand completed the survey.

MEASUREMENTS AND FINDINGS

All participants responded that they routinely offer glycated haemoglobin screening for detection of undiagnosed pre-gestational diabetes, and 92.9% identified that this should occur prior to 20 weeks gestation (as per the national guidelines). However, less than two thirds of midwives thought that all women should be screened for GDM, with 18.2% indicating they would only do this if immediate risk factors were present. There also appeared to be some confusion over the time period for screening for GDM with 22.9% indicating that this should occur later than the guideline-recommended timepoint of 24-28 weeks gestation. Participants who identified as Māori and community-based midwives were most likely to screen for GDM 'only if risk factors were present'. Participants practicing for more than 6 years, those aged 45-54 years, and midwives identifying as Māori were most likely to screen for GDM after 28 weeks (though these did not reach statistical significance).

KEY CONCLUSIONS

The New Zealand Diabetes in Pregnancy screening guidelines do not appear to be well implemented in our sample group, particularly with regard to screening for GDM. This needs to be evaluated in a larger group of midwives, as education around the timeliness and importance of screening for all women may be required.

IMPLICATIONS FOR PRACTICE

A lack of appropriate or timely screening for GDM may mean that women are not being diagnosed or managed appropriately, which in turn may have implications for both mother and child.

Prediabetes and pregnancy: Early pregnancy HbA1c identifies Australian Aboriginal women with high-risk of gestational diabetes mellitus and adverse perinatal outcomes

AIMS

To assess whether early pregnancy HbA_1c can predict gestational diabetes mellitus (GDM) and adverse birth outcomes in Australian women.

METHODS

Prospective study of 466 women without diabetes, aged ≥16-years at first antenatal presentation. Recruitment was from 27 primary healthcare sites in rural and remote Australia from 9-January 2015 to 31-May 2018. HbA_1c was measured with first antenatal investigations (<20-weeks gestation). Primary outcome measure was predictive value of HbA_1c for GDM, by routine 75 g oral glucose tolerance test (OGTT; ≥24-weeks gestation), and for large-for-gestational-age (LGA) newborn.

RESULTS

Of 396 (129 Aboriginal) women with routine OGTT, 28.8% had GDM (24.0% Aboriginal). HbA_1c ≥5.6% (≥38 mmol/mol) was highly predictive (71.4%, 95% CI; 47.8-88.7%) for GDM in Aboriginal women, and in the total cohort increased risk for LGA newborn (RR 2.04, 95% CI; 1.03-4.01, P = 0.040). There were clear differences between Aboriginal and non-Aboriginal women: 16.3% v 5.2% (P < 0.001) had elevated HbA_1c whereas 12.4% v 29.6% (P < 0.001) developed hyperglycemia during pregnancy.

CONCLUSIONS

Early pregnancy HbA_1c ≥5.6% (≥38 mmol/mol) identifies Aboriginal women with apparent prediabetes and elevated risk of having an LGA newborn. Universal HbA_1c at first antenatal presentation could facilitate earlier management of hyperglycemia and improved perinatal outcome in this high-risk population.

A Florida public health-based endocrine clinic for low-income pregnant women with diabetes

OBJECTIVES

To evaluate pregnancy outcomes of low-income women with diabetes-complicated pregnancies who received care from an embedded, public health-based endocrine specialty clinic (ESC) in Florida.

DESIGN

This program evaluation used retrospective chart data to analyze client characteristics, pre-program and during-program glycemic control, and pregnancy outcomes of women enrolled in a prenatal ESC.

SAMPLE

Ninety-two low-income, pregnant women with type 1/type 2 diabetes or gestational diabetes (GDM) comprised this racially/ethnically diverse sample.

VARIABLES/ANALYSIS

Neonatal outcomes included frequencies of prematurity, hypoglycemia, hyperbilirubinemia, and birth weight-for-gestational-age categories. Differences in maternal HbA1C at program entry and mean HbA1C during ESC care were determined by a Wilcoxon and paired sample t test.

RESULTS

HbA1C levels during ESC care (6.9 ± 1.4) were less than program entry HbA1C levels (7.9 ± 1.8) for women with pregestational diabetes (Z = -3.364, p = .001). Among women with GDM, mean HbA1C values during ESC care (5.5 ± 0.4) did not significantly differ (t(51) = -0.532, p > .05) from program entry HbA1C levels (5.5 ± 0.5), suggestive of glycemic goal achievement. No neonatal hypoglycemia or hyperbilirubinemia cases were observed in both groups. Approximately 11% of births were preterm, and 16% of neonates were large-for-gestational-age.

CONCLUSIONS

A public health-based ESC for low-income pregnant women with diabetes may positively affect pregnancy outcomes.

Longitudinal Changes in the Relationship Between Hemoglobin A1c and Glucose Tolerance Across Pregnancy and Postpartum

OBJECTIVE

To characterize the relationship between hemoglobin A1c (HbA1c) levels and glucose tolerance across pregnancy and postpartum.

DESIGN AND PARTICIPANTS

In a longitudinal study of pregnant women with gestational diabetes risk factors (N = 102), we performed oral glucose tolerance testing (OGTT) and HbA1c measurements at 10-15 weeks of gestation, 24-30 weeks of gestation (N = 73), and 6-24 weeks postpartum (N = 42). Complete blood counts were obtained from clinical records. We calculated HbA1c-estimated average glucose levels and compared them with mean OGTT glucose levels (average of fasting, 1- and 2-hour glucose levels). Linear mixed effects models were used to test for longitudinal changes in measurements.

RESULTS

Mean OGTT glucose increased between 10-15 and 24-30 weeks of gestation (β = 8.1 mg/dL, P = .001), while HbA1c decreased during the same time period (β = -0.13%, P < .001). At 10-15 weeks of gestation and postpartum the discrepancy between mean OGTT glucose and HbA1c-estimated average glucose was minimal (mean [standard deviation]: 1.2 [20.5] mg/dL and 0.16 [18.1] mg/dL). At 24-30 weeks of gestation, the discrepancy widened (13.2 [17.9] mg/dL, β = 12.7 mg/dL, P < .001, compared to 10-15 weeks of gestation, with mean OGTT glucose being higher than HbA1c-estimated average glucose). Lower hemoglobin at 24-30 weeks of gestation was associated with a greater discrepancy (β = 6.4 mg/dL per 1 g/dL lower hemoglobin, P = .03 in an age- and gestational age-adjusted linear regression model).

CONCLUSIONS

HbA1c accurately reflects glycemia in the 1st trimester, but underestimates glucose intolerance in the late 2nd trimester. Lower hemoglobin level is associated with greater underestimation. Accounting for gestational age and maternal hemoglobin may improve the clinical interpretation of HbA1c levels during pregnancy.