Diabetic control in pregnancy and intrauterine growth of the fetus

Glycemic targets in pregnancies affected by diabetes: historical perspective and future directions

The definition of optimal glycemic control in pregnancies affected by diabetes remains enigmatic. Diabetes phenotypes are heterogeneous. Moreover, fetal macrosomia insidiously occurs even with excellent glycemic control. Current blood glucose (BG) targets (FBG ≤95, 1-h post-prandial <140, 2 h <120 mg/dL) have improved perinatal outcomes, but arguably they have not normalized. The conventional management approach has been to replicate a pattern of glycemia in normal pregnancy. Although these patterns are lower than previously appreciated, a randomized controlled trial (RCT) has never compared current vs. lower glucose targets powered on maternal/fetal outcomes. This paper provides historical context to the current targets by reviewing evidence supporting their evolution. Using lower targets (FBG <90, 1 h <122, 2 h <110, mean BG ≤95 mg/dL) may help normalize outcomes, but phenotypic differences (type 1 vs. type 2 vs. gestational diabetes) might require different glycemic goals. There remains a critical need for well-designed RCTs to confirm optimal glycemic control that minimizes both small for and large for gestational age across pregnancies affected by diabetes.

Screening for hyperglycaemia in pregnancy: Consensus and controversy

Policy decisions on whether to implement screening programmes depend on whether the proposed programmes meet a set of criteria laid down by the World Health Organization. Screening for hyperglycaemia in pregnancy (HGP) does not meet all the criteria. However the case for screening has been strengthened by a number of recent developments, including: rising prevalence of HGP because of increasing maternal age and BMI; the results of the Hyperglycaemia and Adverse Pregnancy Outcomes study, showing that adverse effects of HGP are seen over a wider range of plasma glucose levels than previously thought; two large trials which showed the benefits of treating lesser degrees of HGP; trials showing that metformin and glibenclamide were effective and safe alternatives to immediate insulin in those without good control on lifestyle measures alone. However uncertainties remain around the threshold for treatment, and on the best screening strategy.

Gestational diabetes and fetal macrosomia in a multi-ethnic population

We set out to examine maternal and neonatal factors surrounding increased birthweight in a multi-ethnic population having an increased prevalence of diabetes mellitus. Additionally, to document the difference (if any) for such neonates in rates of obstetrical operative intervention at delivery where a specific diagnosis of maternal gestational diabetes mellitus had been made. This was an observational study of unselected mothers giving birth to a neonate of 4000 g or more. Data for this population concerning the results of antenatal screening and diagnostic testing for gestational diabetes mellitus were available as a subset of a larger independent and ongoing database. Odds ratios were used to compare group attributes subset on ethnic, diabetic screening and diabetic diagnostic status. Two ethnic groups showed an increased odds ratio for increased birthweight. A diagnosis of diabetes was associated with a twofold increase in caesarean section rate, and a significant increase in median birthweight when compared with screen positive/ diagnostic negative mothers. A total of 70.4% of mothers were overweight or obese while neonatal ponderal index showed a dependence on birthweight ( r2 = 0.17). We conclude that ethnic status is an important factor in assessing fetal size, as is maternal body mass index. A diagnosis of diabetes mellitus confers an increased risk of operative intervention at delivery. Our approach to the use of birthweight data requires re-assessment.

Fetal growth patterns in fetuses of women with pregestational diabetes mellitus

OBJECTIVE

To assess the effect of glucose control on the rate of growth of fetuses in women with pregestational diabetes mellitus (Types 1 and 2).

METHODS

All pregestational diabetic women booked at Mater Mothers' Hospital, Brisbane, Australia, between 1 January 1994 and 31 December 2002, were included. Pregnancies with congenital fetal anomalies, multiple pregnancies, and pregnancies terminated prior to 20 weeks' gestation were excluded. Dating scans were performed before 14 weeks' gestation and serial scans were performed at 18, 24, 28, 32 and 36 weeks. Fetal parameters, including biparietal diameter, femur length and abdominal circumference, were recorded. The daily growth rates for biparietal diameter, femur length, and fetal abdominal area were calculated and compared with those in a low-risk (non-diabetic) population. The growth rates in fetuses of women with satisfactory diabetic control (HbA1c < 6.5%) and unsatisfactory control (HbA1c > or = 6.5%) in the three trimesters were compared.

RESULTS

A total of 174 diabetic pregnancies were included and a total of 997 ultrasound scans were performed. The growth rates for fetuses of mothers with diabetes mellitus were significantly higher than for those in the low-risk population. The z-scores for biparietal diameter, femur length, and fetal abdominal area were 0.18, 0.59 and 1.44, respectively. Fetuses of diabetic mothers with high HbA1c in the first trimester had significantly greater fetal abdominal area growth rate than those with normal HbA1c (fetal abdominal area z-score of 1.7 vs. 0.75, P = 0.009). Although the fetal abdominal area z-scores in fetuses of diabetic mothers with high HbA1c in the second or third trimesters were also higher than those with normal HbA1c levels, the differences did not reach statistical significance. Maternal obesity did not influence the fetal growth rate.

CONCLUSION

The rate of growth of fetuses of diabetic mothers differs from that of the normal population. Growth acceleration persists until the late third trimester. Moreover, periconceptional glucose control appears to have a significant effect on accelerated growth of the fetal abdominal area.

Can ultrasound fetal biometry predict fetal hyperinsulinaemia at delivery in pregnancy complicated by maternal diabetes?

OBJECTIVE

The aim of this study was to determine whether there is an association between ultrasound fetal biometry and amniotic fluid insulin levels at delivery in women with pre-existing diabetes or impaired glucose tolerance in pregnancy.

STUDY DESIGN

This retrospective cohort study identified 93 women who had amniotic fluid insulin levels measured at time of delivery. Standardised estimated fetal weight and fetal growth velocity were calculated from serial third trimester fetal ultrasound measurements.

RESULTS

Women with pre-existing diabetes had significantly greater mean growth velocity [1.39 (95% CI: 0.43-2.23) versus 0.39 (95% CI: -01.7-0.95); p=0.04], significantly greater mean estimated fetal weight (EFW) Z score prior to delivery [2.36 (95% CI: 1.82-2.9) versus 1.38 (95% CI: 1.02-1.74); p=0.002] and greater mean birthweight centile [82 (95% CI: 0.74-0.89) versus 67 (95% CI: 58-76); p=0.02] than those with GDM/IGT. Amniotic fluid insulin levels demonstrated a similar significant difference between the pre-existing and GDM/IGT groups [20.5 (95% CI: 12.9-28.1) versus 8.5 (95% CI: 5.4-11.7); p=0.001]. An association between fetal growth and size and amniotic fluid insulin was observed in women with pre-existing diabetes. Positive likelihood ratios were 1.67 and 2.08, respectively, for the prediction of liquor insulin greater than the 95th centile in women with pre-existing diabetes.

CONCLUSION

Ultrasound measures of fetal size and growth used in this study are not sufficiently accurate to predict those infants likely to be at risk from the adverse effects of fetal hyperinsulinaemia.

Diabetes mellitus in pregnancy in an African population

OBJECTIVES

To compare the pregnancy outcome among diabetic and non-diabetic Nigerian women.

METHODS

A retrospective case record review of 200 pregnant diabetic patients and control was carried out over a 10-year period (1990-1999) at the Maternity unit of the University of Nigeria Teaching Hospital Enugu, Nigeria.

RESULTS

The prevalence of diabetes mellitus among pregnant mothers was 1.7%. Pre-gestational diabetes mellitus accounted for 39% of cases while gestational diabetes was responsible for 61% of them. Late antenatal booking and poor control of diabetes mellitus were common features, while maternal and fetal morbidity was high. Hypertension, vulvovaginitis, premature labor, polyhydramnios and ketoacidosis were significantly higher among diabetic mothers than controls. The perinatal mortality was also higher among diabetics than controls (12.5% vs. 3.5%) with stillbirth being the major contributor. Patients with gestational diabetes were at increased risk of fetal macrosomia than controls (28.7% vs. 5.5%). The overall cesarean section rate was high (36%) among diabetics with previous cesarean section and cephalopelvic disproportion being the commonest indications.

CONCLUSIONS

Health education and provision of modern affordable methods of management of diagnosed cases such as uristix and hemastix will improve maternal and fetal outcome in pregnant diabetics in Africa.

Gestational Diabetes:

Many clinicians in the United States routinely screen all pregnant women in their practices for gestational diabetes. Recently, the US Preventive Services Task Force re-emphasized that such screening is not supported by rigorous scientific evidence. Recommendations for diagnosis and management are based on an even scantier scientific foundation. Although this review questions several aspects of current dogma, it, too, is based on the frequently flawed existing data. It is surprising how, in spite of an abundance of published information on the subject, we continue to be ignorant of the real benefits of the widespread practice of screening and treating for gestational diabetes. The authors hope that the results of a randomized clinical trial, now in progress, will help to resolve some of the controversies surrounding gestational diabetes.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to describe the controversy surrounding the significance of gestational diabetes, to break down the data regarding the efficacy of screening for gestational diabetes, and to outline potential treatment options for gestational diabetes.

The ultrasound assessment of adipose tissue deposition in fetuses of "well controlled" insulin-dependent diabetic pregnancies

OBJECTIVE

To assess differences in adipose deposition in fetuses from normal pregnancies and women with diabetes.

RESEARCH DESIGN AND METHODS

The study group consisted of 15 well controlled insulin-dependent women with diabetes and 16 controls with a normal glucose. Ultrasound measurements were taken of subcuticular tissue thickness at the abdominal and suprascapular level at 31 and 37 weeks gestation. Triceps and subscapular skinfold thickness were also measured at birth.

RESULTS

Gestational age at delivery and birthweights were not significantly different. At 31 weeks, fasting glucose levels were 5.0 +/- 1 mmol/l for diabetic vs. 3.3 +/- 0.3 mmol/l for controls (P < 0.01), post-prandial 5.6 +/- 0.4 vs. 5.1 +/- 0.3 mmol/l (P < 0.01). At 37 weeks, they were 4.6 +/- 0.2 mmol/l vs. 3.8 +/- 1.1 mmol/l (P < 0.01) and 6.0 +/- 0.6 mmol/l vs. 5.3 +/- 0.3 mmol/l (P < 0.01). Abdominal and suprascapular subcuticular thickness were 4.4 +/- 0.1 mm vs. 3.7 +/- 0.1 mm (P < 0.05) and 4.3 +/- 0.2 mm vs. 3.5 +/- 0.2 mm (P < 0.05) at 31; 5.6 +/- 0.2 mm vs. 4.8 +/- 0.1 mm (P < 0.05) and 5.4 +/- 0.2 mm vs. 4.4 +/- 0.1 mm (P < 0.05) at 37 weeks. At birth, triceps and suprascapular skinfolds were 4.7 +/- 0.1 mm vs. 4.1 +/- 0.1 mm (P < 0.05) and 4.7 +/- 0.2 mm vs. 3.8 +/- 0.1 mm (P < 0.01).

CONCLUSION

Adipose tissue disposition is increased in fetuses of women with well-controlled diabetes. This may be a reflection of higher maternal glucose levels in these women and may explain why even well-controlled diabetic pregnancies are at risk of macrosomia.

Fetal growth spurt and pregestational diabetic pregnancy

OBJECTIVE

To assess the timing of fetal growth spurt among pre-existing diabetic pregnancies (types 1 and 2) and its relationship with diabetic control. To correlate fetal growth acceleration with factors that might influence fetal growth.

RESEARCH DESIGN AND METHODS

This retrospective study involved all pregestational diabetic pregnancies delivered at a tertiary obstetric hospital in Australia between 1 January 1994 and 31 December 1999. Pregnancies with major congenital fetal anomalies, multiple pregnancies, small-for-gestational-age pregnancies (<10th centile), and those that were terminated before 20 weeks were excluded. In this cohort, pregnancies delivered at term had at least four ultrasound scans performed. The first scans were performed before 14 weeks of gestation and were regarded as dating scans. Abdominal circumference measurements were retrieved from the ultrasound reports. The z-scores for abdominal circumferences, according to the gestational age, were calculated. The gestations when the ultrasound scans were performed were stratified at four weekly intervals beginning at 18 weeks and continuing through the rest of the study. Majority of these diabetic pregnancies had ultrasound scans performed at 18, 28, 32, and 36 weeks. The abdominal circumference z-scores for pregnancies with large-for-gestational-age (LGA) babies (>90th centile for gestation) were compared with babies with normal birth weights.

RESULTS

A total of 101 diabetic pregnancies were included. Diabetic mothers, who had LGA babies, had significantly higher prepregnancy body weight and BMI (P < 0.05). There were no differences in maternal age or parity among the two groups. There were also no differences in the first-, second-, and third-trimester HbA(1c) levels between the two groups. The abdominal circumference z-scores were significantly higher for LGA babies from 18 weeks and thereafter. The differences increased progressively as the gestation advanced. Maximum difference was noted in the third trimester (30-38 weeks).

CONCLUSIONS

Fetal growth acceleration in LGA fetuses of diabetic mothers starts in the second trimester, from as early as 18 weeks. In this study, glucose control did not appear to have a direct effect on the incidence of LGA babies, and such observation might result from the effects of other confounding factors.

Effect of fetal hyperinsulinism on oral glucose tolerance test results in patients with gestational diabetes mellitus

OBJECTIVE

This study was undertaken to evaluate the impact of the fetoplacental glucose steal phenomenon on the results of oral glucose tolerance testing in pregnancies complicated by gestational diabetes mellitus with fetal hyperinsulinism.

STUDY DESIGN

This was an analysis of the cases of 34 patients with two consecutive abnormal oral glucose tolerance test results and amniotic fluid insulin measurement before institution of insulin therapy. Patients were divided into groups on the basis of normal versus elevated amniotic fluid insulin concentrations.

RESULTS

Oral glucose tolerance tests were done at a mean (+/-SD) of 24.9 +/- 5.7 and 30.7 +/- 3.2 weeks' gestation, and amniotic fluid insulin measurements were done at 31.1 +/- 3.2 weeks' gestation. In 13 women with gestational diabetes mellitus with normal amniotic fluid insulin concentration, maternal postload blood glucose levels at 1 hour increased by 12 mg/dL (168 vs 180 mg/dL; 9.3 vs 10.0 mmol/L; P = .0006) during the course of 6 weeks. In contrast, in 21 women with gestational diabetes mellitus with elevated amniotic fluid insulin levels (>7 microU/mL; >42 pmol/L), 1-hour postload blood glucose levels decreased by 22 mg/dL (201 vs 179 mg/dL; 11.2 vs 9.9 mmol/L; P = .002) during the same period. The higher the amniotic fluid insulin level, the larger the decrease (R = 0.504; P =.02). Although low amniotic fluid insulin levels were correlated significantly with 1-hour glucose levels of the first and second oral glucose tolerance tests, high insulin levels were no longer correlated with the second oral glucose tolerance test.

CONCLUSION

Exaggerated fetal glucose siphoning may provide misleading oral glucose tolerance test results in pregnancies complicated by fetal hyperinsulinism by blunting maternal postload glucose peaks. Consequently, oral glucose tolerance test results in a pregnancy complicated by gestational diabetes mellitus with a fetus that already has hyperinsulinemia may erroneously be considered normal.

Factors affecting fetal weight distribution in women with type I diabetes

OBJECTIVE

To identify factors independently affecting fetal weight in women with type I diabetes.

DESIGN

Prospectively recorded data in consecutive women with type I diabetes, between 1975-1992.

SETTING

Simpson Memorial Maternity Hospital, Edinburgh. Population Three hundred and two pregnancies with type I diabetes identified before pregnancy, with antenatal care and delivery in the Simpson Memorial Maternity Hospital, a singleton pregnancy, and the same diabetic physician.

METHODS

Normal ranges for birthweight were established for the total hospital population. All cases and the total population had pregnancy dating by ultrasound. The relation between standardised birthweight and explanatory variables was investigated using correlation analysis, t tests and chi2 tests as appropriate, and subsequently using multiple linear regression.

RESULTS

Standardised birthweight in cases, compared with the reference population, showed a unimodal, approximately normal distribution, markedly shifted to the right (mean + 1.26 SD). The most predictive variable was glycated haemoglobin concentration at 27-33 weeks, which explained 6.3% of the birthweight variance, while smoking explained 2.7% and maternal weight 2.0%. There was a trend towards a negative relationship with glycated haemoglobin concentration at 6-12 weeks. Smoking and glycated haemoglobin concentration were strongly intercorrelated.

CONCLUSIONS

Most of the variance in standardised birthweight remains unexplained, but glycated haemoglobin concentration at 27-33 weeks is the most powerful explanatory variable. Possible reasons why there is not a stronger relationship between markers of maternal glycaemia and birthweight are discussed.

Amniotic fluid insulin levels identify the fetus at risk of neonatal hypoglycaemia

AIMS

To investigate the use of amniotic fluid insulin (AFI) as a predictor of neonatal morbidity in the macrosomic newborn of the diabetic mother, in view of the fact that raised AFI levels are a marker for fetal hyperinsulinaemia.

METHODS

AFI was measured by radioimmunoassay in a group of pregnant diabetic women (n = 63) with normal (n = 41) or accelerated fetal growth (n = 22).

RESULTS

Using log transformed data, liquor insulin was found to be significantly higher in pregnant women with Type 1 and Type 2 diabetes mellitus (17.6 mU/l; 95% confidence interval (CI) 11.7-26.4) compared with women with gestational diabetes mellitus (GDM) (8.2 mU/l; 95% CI 4.8-13.8, P = 0.02) or impaired glucose tolerance (IGT) (6.2mU/l; 95% CI 4.9-8.0, P = 0.0001). In the group with macrosomic fetuses (birth weight > 90th centile for gestational age), there was a significantly higher incidence of elective Caesarean section (CS) and emergency CS (12/22) compared to those with appropriate for gestational age (AGA) fetal weights (birth weight > 10th and < 90th centiles for gestational age) (9/41, P = 0.009). There was no significant correlation between raised AFI and macrosomia except in the Type 1 diabetic women, in whom the AGA group mean was 13.2 mU/l (95% CI 7.4-23.3), and 34.6mU/l (95% CI 17.5-68.4 P = 0.022) in macrosomia. In the latter group, hypoglycaemia requiring treatment was significantly more common in the macrosomic hyperinsulinaemic neonates (8/13), compared to normoinsulinaemic neonates in the same group (0/9, P = 0.005).

CONCLUSIONS

Identification of the hyperinsulinaemic fetus before delivery might allow the intensification of maternal insulin therapy leading to a reduction in incidence and severity of diabetic fetopathy. Pregnancy with a normoinsulinaemic fetus could be allowed to continue to the onset of spontaneous labour, which might result in a lower CS rate.

Amniotic fluid insulin testing in gestational diabetes: safety and acceptance of amniocentesis

OBJECTIVES

We analyzed the safety and patient acceptance of amniotic fluid insulin measurements by third-trimester amniocentesis in women with gestational diabetes mellitus.

STUDY DESIGN

We studied the rate of early uterine contractions, need for tocolysis, premature rupture of membranes, mode of delivery, length of gestation, and fetal weight and length at birth in 194 women with gestational diabetes mellitus who underwent third-trimester amniocentesis and 268 controls. Patient acceptance of amniocentesis was assessed prospectively with a visual rating scale and a semistructured interview comparing 50 women with gestational diabetes mellitus to 50 women undergoing second-trimester amniocentesis for fetal karyotyping.

RESULTS

Only the length of gestation differed significantly but without clinical relevance (39.5 +/- 1.9 vs 40.0 +/- 2.0, P = .006) between women with gestational diabetes mellitus who had amniocentesis and controls. Patient acceptance was equally high both for second-trimester and third-trimester amniocentesis.

CONCLUSIONS

Third-trimester amniocentesis for measuring amniotic fluid insulin is safe and well accepted by the patients. This is important information both for treating and counseling women with gestational diabetes mellitus.

Cord blood insulin to assess the quality of treatment in diabetic pregnancies

According to the Pedersen hypothesis, fetal hyperinsulinism is the major cause for adverse neonatal outcome. We investigated associations between insulin levels in cord blood and fetal complications. Three groups of 21 insulin-dependent diabetic patients with different insulin levels in cord blood were matched according to White Classes. Insulin levels in cord blood of < 20 microU/ml were considered normal (controls), 20-50 microU/ml intermediate group, and > 50 microU/ml high (cases). The mean (+/-S.D.) insulin level in cord blood in the three groups was 10.7+/-5.6, 28.6+/-8.1, and 104.0+/-61.0 microU/ml, respectively. Controls and cases showed significant differences in birth weight > 90th percentile (9.5% vs. 76.2%), premature birth < 37 weeks (4.8% vs. 71.4%), caesarean delivery (28.6% vs. 66.4%), hypoglycaemia of the neonate (14.3% vs. 61.9%), cushingoid appearance (4.8% vs. 42.9%) and respiratory distress syndrome (0% vs. 33.3%). The results of the intermediate group were between the controls and the cases. Insulin levels in cord blood > 20 microU/ml represent a continuum of increasing diabetogenic fetopathy. We consider neonates with insulin levels in cord blood < 20 microU/ml as metabolically healthy, those with 20-50 microU/ml as having mild fetopathy, and those with > 50 microU/ml as having marked fetopathy, respectively.

Gestational and pre-gestational diabetes: comparison of maternal and fetal characteristics and outcome

OBJECTIVE

To determine the incidence of antenatal and intrapartum maternal and fetal complications of gestational diabetes mellitus (GDM) and compare them with pre-gestational diabetes mellitus (pre-GDM) and non-diabetic pregnancies in our population.

STUDY DESIGN

Nine-hundred and seventy-two women with gestational diabetes mellitus and 71 women with pre-gestational diabetes mellitus, and their offspring (delivered in our hospital between January 1991 and April 1994) were studied. Maternal and fetal prenatal and intrapartum complications were analyzed.

RESULTS

The incidence of GDM was 9.8%. The maternal complications included higher incidences of cesarean section and perineal lacerations in GDM and pre-GDM patients than in the non-diabetic pregnancies, and higher rates of macrosomia and hypoglycemic episodes in their offspring.

CONCLUSION

The incidence of maternal, fetal and neonatal complications in GDM is similar to pre-GDM patients and their offspring. Both GDM and pre-GDM pregnancies and the offspring should, therefore, be monitored and managed identically.