Amniotic fluid glucose concentration

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.

Correlation of amniotic fluid glucose concentration and intraamniotic infection in patients with preterm labor or premature rupture of membranes

Amniotic fluid glucose concentration has previously been suggested as a rapid and sensitive test for diagnosing intraamniotic infection. In this study, 204 patients less than or equal to 34 weeks estimated gestational age with preterm labor or premature rupture of membranes underwent amniocentesis to detect subclinical intraamniotic infection. Amniotic fluid was cultured for aerobic and anaerobic bacteria, as well as for Mycoplasma species. Amniotic fluid glucose levels were significantly lower in patients with positive amniotic fluid cultures than in patients with negative cultures (median, 10 mg/dl; range, 1 to 62 mg/dl vs median, 31 mg/dl; range, 2 to 126 mg/dl, respectively; p less than 0.001). In terms of predicting amniotic fluid culture results, an amniotic fluid glucose concentration of less than or equal to 16 mg/dl had a sensitivity of 79%, specificity of 94%, positive predictive value of 87%, and negative predictive value of 90%. The determination of amniotic fluid glucose concentration is useful in detecting subclinical intraamniotic infection in patients less than or equal to 34 weeks estimated gestational age with preterm labor or premature rupture of membranes.

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.

Phosphoenolpyruvate carboxykinase activity in human amniotic fluid

Amniotic fluid samples obtained from normal pregnancies during gestation were used to quantitate the levels of phosphoenolpyruvate carboxykinase (PEPCK) activity. It is concluded that: (1) PEPCK activity was highest in the amniotic fluid cells of midtrimester pregnancies as compared to those of pregnancies close to term; (2) the activity of PEPCK seen in the amniotic fluid supernatant was about one fourth to one half of that seen in the amniotic cells; (3) the amniotic fluid supernatant PEPCK activity fluctuated very little during the entire gestation.

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.

Amniotic fluid glucose in pregnancies complicated by diabetes

Amniotic fluid glucose (AF glu) was studied in 92 pregnancies complicated by maternal diabetes. An inverse relation between AF glu and gestational age was found: [AF glu (mg. per diciliter) = 160.9 -- 3.51 (weeks gestation); r = -0.47]. A direct relation between AF glu and severity of maternal diabetes was observed: mean AF glu (mg. per deciliter) = 24.6 +/- S.D. 12.3 in Class A, 41.2 +/- 25.5 in Class AD and 57.5 +/- 36.5 in Classes B-D. A positive correlation of AF glu with osmolality was observed [AF Osm (mOsm. per kilogram) = 250.7 + 0.22 AF glu; r = +0.50], but this relation was remarkable inconsistent in individual patients. Neither individual nor serial AF glu levels were of any prognostic value in predicting fetal condition or perinatal outcome.