Postpartum oral glucose tolerance tests in mothers of macarosomic infants: inadequacy of current antenatal test criteria in detecting prediabetic state

Postpartum metabolic function in women delivering a macrosomic infant in the absence of gestational diabetes mellitus

OBJECTIVE

Gestational diabetes mellitus (GDM) is associated with fetal macrosomia and maternal postpartum dysglycemia, insulin resistance, and β-cell dysfunction. Indeed, in practice, a prior pregnancy that resulted in a large-for-gestational-age (LGA) delivery is often considered presumptive evidence of GDM, whether or not it was diagnosed at the time. If this clinical assumption is correct, however, we would expect these women to exhibit postpartum metabolic dysfunction. Thus, to test this hypothesis, we assessed metabolic function during and after pregnancy in a cohort of women stratified according to the presence/absence of GDM and LGA delivery, respectively.

RESEARCH DESIGN AND METHODS

A total of 562 women underwent metabolic characterization, including oral glucose tolerance test (OGTT), in late pregnancy and at 3 months' postpartum. The women were stratified into three groups: those with neither GDM nor LGA delivery (nonGDM, n = 364), those without GDM but with LGA delivery (nonGDM-LGA, n = 46), and those with GDM (n = 152).

RESULTS

On logistic regression, GDM predicted postpartum glucose intolerance (OR 4.1 [95% CI 2.5-6.8]; P < 0.0001), whereas nonGDM-LGA did not (P = 0.65). At 3 months' postpartum, the mean adjusted levels of fasting glucose and area under the glucose curve on the OGTT were significantly higher in the GDM women compared with either nonGDM or nonGDM-LGA (all P < 0.05), with no differences between the latter two groups. In a similar manner, mean adjusted insulin sensitivity (Matsuda index) and β-cell function (Insulin Secretion-Sensitivity Index-2) were lower in GDM women compared with either nonGDM or nonGDM-LGA (all P < 0.05), again with no differences between the latter two groups.

CONCLUSIONS

Women with nonGDM-LGA do not exhibit postpartum metabolic dysfunction, arguing against the assumption of undiagnosed GDM in these patients.

Insulin resistance in Hispanic large-for-gestational-age neonates at birth

CONTENT

Intrauterine exposure to maternal diabetes and large size at birth are known risk factors for the subsequent development of insulin resistance and metabolic syndrome. Although Hispanic youth have been shown to have a high prevalence of metabolic syndrome, it is unknown whether metabolic abnormalities and a predisposition for glucose intolerance are present at birth.

OBJECTIVE

The objective of the study was to determine whether abnormalities in insulin sensitivity exist at or soon after birth in large-for-gestational-age neonates born to Hispanic women with and without gestational diabetes. DESIGN/PATIENTS/SETTING: Forty-two term Hispanic neonates were enrolled for cross-sectional studies at 24-48 h after birth and included nine large-for-gestational-age neonates delivered of women with gestational diabetes (large-for-gestational-age-IDM), 12 large-for-gestational-age but not IDM neonates, 11 poorly grown (at the fifth to 10th percentile), and 10 appropriate-for-gestational-age neonates. Insulin sensitivity and secretion were measured by shortened fasting iv glucose tolerance test.

MAIN OUTCOME MEASURE

Insulin sensitivity index was measured within 48 h of birth.

RESULTS

Neonates were studied at 36 +/- 11 h postnatally, and all groups were euglycemic at the time of study. However, insulin sensitivity was significantly lower (P < 0.05, ANOVA) in large-for-gestational-age-IDM [3.0 +/- 0.7 (sem) mU/liter.min] and large-for-gestational-age-non-IDM (2.2 +/- 0.4 mU/liter.min) cohorts in comparison with poorly grown (5.0 +/- 0.7 mU/liter.min) and appropriate-for-gestational-age controls (5.4 +/- 0.8 mU/liter.min). Insulin secretion did not differ between groups.

CONCLUSIONS

Reduced insulin sensitivity is present soon after birth in Hispanic large-for-gestational-age neonates born to mothers with and without gestational diabetes, demonstrating the onset of insulin resistance before birth and evidence of altered fetal programming.

False-Positive 1-Hour Glucose Challenge Test and Adverse Perinatal Outcomes

OBJECTIVE

To determine whether a false-positive 1-hour glucose challenge test (GCT) is associated with perinatal complications.

METHODS

We performed a retrospective cohort study of 1825 eligible pregnant women among a cohort of 1998 patients. Patients were screened for gestational diabetes mellitus (GDM) with the 1-hour 50-g GCT at 24-28 gestational weeks. A false-positive GCT was defined as a result greater than or equal to 135 mg/dL followed by a normal 3-hour glucose tolerance test (GTT). We compared the negative GCT and false-positive GCT cohorts for a composite perinatal outcome variable that included fetal macrosomia, antenatal death, shoulder dystocia, chorioamnionitis, preeclampsia, intensive care nursery admission, and postpartum endometritis. Secondary outcomes included cesarean delivery and each component variable of the composite. Unadjusted, stratified, and multiple logistic regression analyses were used to investigate the association between a false-positive GCT and the development of perinatal complications.

RESULTS

We identified 164 patients with a false-positive GCT and 50 patients with GDM. The false-positive GCT cohort on average was older, of higher parity, had a higher body mass index, and more frequently had chronic hypertension, sickle cell trait, and elevated midtrimester human chorionic gonadotropin levels. The false-positive GCT cohort more frequently had adverse perinatal outcomes, including the composite perinatal outcome (odds ratio [OR] 5.96, 95% confidence interval[CI]1.47,24.16), macrosomia greater than 4500 g (OR 3.66, 95% CI 1.30, 10.32), antenatal death (OR 4.61, 95% CI 0.77, 27.48), shoulder dystocia (OR 2.85, 95% CI 1.25, 6.51), endometritis (OR 2.18, 95% CI 1.03, 4.63), and cesarean delivery (OR 1.76, 95% CI 0.99, 3.14).

CONCLUSION

A false-positive GCT is an independent risk factor for adverse perinatal outcomes.

Neonatal echocardiograms of macrosomic neonates

OBJECTIVE

To compare echocardiograms of macrosomic and healthy full term neonates whose weight was appropriate for gestational age (AGA).

METHODS

Echocardiography was performed on 9 healthy full term AGA neonates and 15 macrosomic neonates. A data base was generated from valid echocardiographic measurements on each infant.

RESULTS

Macrosomic infants were heavier than control infants and had a greater body surface area, but their mean cardiac dimensions were similar. The mean LVES volume was smaller than that of the control group when expressed as a fraction of individual LVED values (0.61 +/- 0.04 vs 0.64 +/- 0.02; p = 0.02). When comparing IVS/PW, it was observed that the ratio was up to and including 1.33 in the control group, while the upper limit of the ratio of the nondiabetic macrosomic infants was 1.6. The shortening fraction (SF%) was increased in comparison to infants of normal weight (40.67% +/- 3.34 vs 36.00% +/- 1.89; p = 0.0009). The thickened IVS did not elevate SF% by decreasing LVES; the macrosomic infants had a smaller LVES mean volume.

CONCLUSION

IVS/PW ratio of macrosomic infants fell outside of the normal range. Macrosomic neonates were found to have an increased SF% secondary to a proportionally smaller LVES volume, regardless of IVS thickness.