Amniotic fluid glucose in pregnancies complicated by diabetes

Amniotic fluid glucose at the time of genetic amniocentesis: correlation with duration of pregnancy and birthweight

OBJECTIVE

To test whether amniotic fluid (AF) glucose levels in 15-18 weeks of pregnancy can predict birthweight and duration of pregnancy.

STUDY DESIGN

In this prospective study, 66 non-diabetic pregnant women underwent amniocentesis between 15 and 18 weeks of pregnancy and glucose levels were measured immediately by using the enzymatic method of hexocinase. They were all followed up and delivered in our department and neognological parameters were recorded.

RESULTS

AF glucose values ranged from 12 to 69mg/dl (mean 44.2mg/dl, S.D. 11.6mg/dl). No linear relationship was found between AF glucose and either birthweight or duration of pregnancy.

CONCLUSION

AF glucose values between 15 and 18 weeks of pregnancy did not correlate with either birthweight or duration of pregnancy. A single measurement of this value cannot be used for the prediction of the factors studied.

Vitamin D3 metabolites in amniotic fluid in relation with maternal and fetal sera in term pregnancies

The concentration of 25-hydroxyvitamin D3 (25(OH)D3), 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) were determined in amniotic fluid, fetal cord serum and maternal serum in 26 cases of elective cesarean sections at term. All the women had a normal pregnancy and did not get any vitamin D fortified preparations. The samples were collected during December 1982-April 1983, at 37-40 weeks of pregnancy. The respective levels (+/- S.D.) of 25(OH)D3, 24,25(OH)2D3 and 1,25(OH)2D3 in maternal serum were: 18.03 +/- 10.8 ng/ml, 1.473 +/- 1.562 ng/ml and 36 +/- 21.5 pg/ml; in fetal cord serum: 13.15 +/- 8.3 ng/ml, 0.9 +/- 0.76 ng/ml and 29.2 +/- 18.55 pg/ml and in amniotic fluid: 0.732 +/- 0.508 ng/ml, 0.212 +/- 0.104 ng/ml and 14.3 +/- 10.0 pg/ml. The levels of the three metabolites in maternal and fetal cord serum were not statistically different. There was a statistically significant correlation between maternal and fetal serum levels of 25(OH)D3 and 24,25(OH)2D3 (r = 0.79, p less than 0.01 and r = 0.743, p less than 0.01 respectively). No significant correlation was found in 1,25(OH)2D3 levels between maternal and fetal cord sera. This lack of correlation may well be in agreement with the recent findings of Kouppala, et al. who demonstrated that the fetus contributes to its own pool of 1,25(OH)2D3. A significant difference was found between maternal serum and amniotic fluid levels of the three metabolites. A statistically significant difference was also found between fetal serum levels of 25(OH)D3 and 24,25(OH)2D3 and amniotic fluid levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluoride concentration in amniotic fluid and fetal cord and maternal plasma

Fluoride concentrations were determined in plasma of 50 pregnant women, 44 samples of amniotic fluid and fetal cord blood of 29 fetuses at various stages of normal pregnancies, from an area with a relatively low water fluoride (less than 0.5 ppm) content. The mean concentrations of fluoride from maternal plasma, cord plasma and amniotic fluid (+/- S.D.) were 0.033 +/- 0.003, 0.028 +/- 0.005 and 0.017 +/- 0.003 ppm, respectively. Maternal and fetal plasma fluoride concentrations did not differ significantly. In the older age group fetal cord plasma fluoride concentration was significantly lower than maternal plasma levels (0.012 +/- 0.08 ppm vs. 0.023 +/- 0.001, respectively; p less than 0.05). Amniotic fluid fluoride levels were significantly higher at term than in midtrimester pregnancy, 0.017 +/- 0.0018 vs. 0.010 +/- 0.009 ppm (P less than 0.05), respectively. This higher concentration may imply higher fetal urinary excretion of fluoride at term due to the lower sequestration of fluoride as the process of bone calcification is more complete.

The effect of gestational age on amniotic fluid glucose in pregnancy complicated by diabetes mellitus

Amniotic fluid glucose was measured in 189 amniotic fluid samples from 117 well-controlled Class A to F diabetic pregnant women from 32 to 40 weeks' gestation. A simultaneous maternal plasma glucose level was determined at each amniocentesis. Samples were obtained with the mother in the fasting or nonfasting (3.8 hours after breakfast) state. Amniotic fluid glucose correlated significantly with simultaneous maternal glucose (r = 0.562; p = 0.001). A significant downward linear trend of mean amniotic fluid glucose with advancing gestational age was demonstrated (p less than 0.01). No trend of mean simultaneous maternal glucose with gestational age was seen. These results were not affected by maternal prandial status at the time of amniocentesis. It is concluded that amniotic fluid glucose decreases with advancing gestational age in well-controlled diabetic pregnant women independent of maternal glycemic levels. Studies of amniotic fluid glucose and/or its relationship to other metabolic hormones must take this into account.

Significance of amniotic fluid glucose in pregnancy

Amniotic fluid glucose values were measured in 285 women with normal and abnormal pregnancies. A progressive decrease in glucose values was observed with advancing gestation. Complications in pregnancy did not influence the amniotic fluid glucose value for the given gestational age. In patients with diabetes, very high levels were found, but these progressively decreased with advancing gestation. Since abnormal conditions in pregnancy, other than diabetes, do not affect the amniotic fluid glucose level, it seems to be a reliable tool in assessing fetal maturity. Values above 15 mg/100 ml rule out term pregnancies and those below 5 mg/100 ml, prematurity.

Current concepts of amniotic fluid dynamics

Amniotic fluid at term in the human is the product of numerous exchanges with the fetal and indirectly, the maternal compartments. Our current information on the formation, circulation, and removal of this fluid is limited but provides an interesting concept of the steady-state regulation of this space. Further confirmation of this model comes from data describing drug exchange between mother, fetus, and amniotic fluid.

Amniotic epithelium in diabetes mellitus. Light and electron microscopic examination

The epithelium of human amnion was examined under the light and electron microscopes. Morphologically, the amniotic epithelium in diabetes mellitus differs from that of a normal term specimen by the following characteristics: 1. An increase in the number of beta-shaped glycogen granules and lipid droplets; 2. The presence of epithelial areas with dead cells; 3. Thickening of the basal membrane. Areas with dead cells could be identified in the amniotic epithelium of diabetic patients. These were not found in normal term pregnancies nor in other types of high-risk pregnancies, such as non-diabetic hydramnios, rhesus incompatibility, or pretoxaemia/toxaemia. These findings may indicate that the areas are specific to diabetes mellitus.

Changes in amniotic fluid glucose, beta-hydroxy-butyrate, glycerol, and lactate concentration in diabetic pregnancy

Amniotic fluid glucose, beta OH butyrate, glycerol, and lactate concentrations were measured in 75 samples collected in the third trimester of pregnancy from 50 diabetic patients, all but four of whom required insulin. Increases in maternal fasting plasma sugar were accompanied by corresponding increases in amniotic fluid glucose and on occasion increases in amniotic fluid beta OH butyrate. These data correspond to previous reports of placental glucose transfer and in addition, provide statistically significant evidence of placental betaOH butyrate transfer since the hyperglycemic, hyperinsulinemic fetus of a diabetic mother would be a poor primary source for ketogenesis. Relatively poor correlation of elevated fluid levels of these solutes to fetal outcome probably reflects a low incidence of maternal hyperglycemia, ketogenesis. Relatively poor correlation of elevated fluid levels of these solutes to fetal outcome probably reflects a low incidence of maternal hyperglycemia, ketoacidosis, and over-all reduced neonatal morbidity-mortality rates in this group of metabolically well-controlled, predominantly insulin-requiring diabetic patients managed in a regional high-risk perinatal center.

Significance of amniotic fluid glucose in late pregnancy

Glucose levels were estimated in over 150 amniotic fluid samples and were found to fall with advancing gestational age. Significantly lower levels were found in post-term pregnancies and in association with fetal growth retardation. Amniotic fluid glucose estimation was found to be superior to human placental lactogen in distinguishing between normal pregnancies and those complicated by fetal growth retardation. The role of the membranes in influencing the level of amniotic fluid glucose was investigated using in vitro perfusion experiments. The permeability of the membranes to glucose decreased with advancing gestational age.