Volume 200, Issue 5 , Pages e43-e44, May 2009
Correlation of glucose concentrations in maternal serum and amniotic fluid in high-risk pregnancies
Article Outline
Objective
We sought to determine whether a correlation exists between maternal serum glucose and amniotic fluid glucose in high-risk pregnancies.
Study Design
We conducted a prospective cross-sectional study of 60 patients, between 15 and 38 weeks' gestation, undergoing amniocentesis between March 2006 and April 2007. Participants underwent amniocentesis with evaluation of amniotic fluid glucose and maternal finger stick glucose. Data were collected on maternal demographics, gestational age, presence of diabetes or chorioamnionitis, use of betamethasone, and body mass index. Statistical analyses included Spearman ρ correlations.
Results
A positive correlation was found between maternal serum glucose and amniotic fluid glucose (r = 0.401, P < .01), and amniotic fluid index and diabetes (r = 0.367, P < .05). An inverse correlation was found between amniotic fluid glucose and chorioamnionitis (r = -0.499, P < .01).
Conclusion
Maternal hyperglycemia directly influences amniotic fluid glucose levels and may result in an elevated amniotic fluid glucose value.
Key words: amniotic fluid, chorioamnionitis, serum glucose
Background and Objective
Previous studies have shown that the mean amniotic fluid glucose concentration increases slightly between the 14th and 17th week of pregnancy followed by a decrease in the third trimester.1, 2 Researchers have suggested that changes in maternal serum concentrations influence the amniotic fluid glucose concentration.3, 4 However, to the best of our knowledge, no studies have provided a correlation of maternal serum glucose and finger stick fluid glucose outside of pregnancies complicated by diabetes.
Our goal was to determine whether there is a correlation between maternal finger stick glucose and amniotic fluid glucose in high-risk pregnancies. We hypothesized that there is a positive correlation between maternal serum glucose and amniotic fluid glucose levels.
Materials and Methods
We designed a prospective cross-sectional study open to patients undergoing an amniocentesis for genetic, fetal lung maturity, and/or chorioamnionitis analysis during their hospitalization on our antepartum obstetric department between March 2006 and April 2007. Institutional review board approval was acquired prior to initiation of the study and informed consent was obtained from each participant.
All amniocenteses were performed by a sterile transabdominal approach under ultrasound guidance and amniotic fluid glucose level was determined via analysis in our chemistry laboratory and expressed as mg/dL. Maternal glucose can be measured as venous or capillary blood and diagnostic criteria frequently provide equivalence estimates for these 2 methods. Capillary glucose meters are regulated and accurate to within ±10% of a reference laboratory glucose value. In 2007, Karon et al5 found no significant differences between median capillary blood and laboratory glucose levels when using the Accu-chek Inform glucometer (Roche, Mannheim, Germany).
Maternal finger stick blood sugar values were obtained by a registered nurse or patient care assistant within 1 hour of the amniocentesis by using a glucometer (Accu-chek Inform; Roche). A diagnosis of diabetes was determined based on patient diabetes prior to pregnancy or gestational diabetes secondary to 2 abnormal values on a 100-g glucose tolerance test. Chorioamnionitis was defined as maternal temperature (≥ 100.4°F), fundal tenderness, fetal tachycardia with signs of premature rupture of membranes and/or preterm labor, or amniotic fluid glucose < 15 mg/dL with a positive gram stain result; a single parameter is not diagnostic of chorioamnionitis. Prior to the amniocentesis, amniotic fluid index was determined via a 4-quadrant analysis.
Statistical analyses were performed using software (SPSS, Version 15.0; SPSS Inc, Chicago, IL). Spearman ρ correlations were computed for glucose concentrations and considered statistically significant when P < .05.
Results
In all, 60 patients participated in the study, 18 (29%) were diabetic and 8 (13%) had chorioamnionitis. Median gestational age at amniocentesis was 33.71 ± 6.41 weeks and gravidity was 2.00 ± 2.01. Average maternal age was 26.42 ± 7.44 years and body mass index was 31.02 ± 7.02 kg/m2. Amniotic fluid index, finger stick glucose, and amniotic glucose values are shown in the Figure. Among all participants, a positive correlation was found between glucose concentration in maternal serum and amniotic fluid (r = 0.401, P < .01). Specifically, as maternal serum glucose values increased, the amniotic fluid glucose value increased. A correlation did not exist between maternal serum glucose and amniotic fluid index.
FIGURE.
High-risk pregnancy group
Comparison of chorioamnionitis and diabetic amniotic fluid and fingerstick glucose levels
Rinala. Correlation of glucose concentrations in maternal serum and amniotic fluid in high-risk pregnancies. Am J Obstet Gynecol 2009.
Of the 18 patients with diabetes, a moderately positive correlation was found between diabetes and amniotic fluid glucose (r = 0.284, P < .05) and between diabetes and amniotic fluid index (r = 0.367, P < .05). We found an inverse relationship between amniotic fluid glucose value and the presence of chorioamnionitis (r = -0.499, P < .01). As the amniotic fluid glucose level declined, the risk of chorioamnionitis increased.
Comment
Our study design enabled us to evaluate amniotic glucose values between 15 and 38 weeks' gestation with respect to maternal serum finger stick glucose within 1 hour of obtaining amniotic fluid. We confirmed our hypothesis that a positive correlation exists between maternal serum glucose and amniotic glucose. Our findings support those of Dashe et al,3 who suggested that changes in maternal serum concentrations influence the amniotic glucose concentration, but our study specifically elucidates the relationship between maternal serum and amniotic glucose concentrations in patients with diabetes. In 1993, Romero et al6 showed that low levels of amniotic fluid glucose (< 15 mg/dL) are 96% specific for chorioamnionitis. We also found that low levels of amniotic fluid glucose were positively correlated to chorioamnionitis.
Our study is of clinical importance as it shows that amniotic fluid glucose is independent of the amniotic fluid index. Therefore, the amniotic fluid glucose value is a reliable measure at the 5th or 95th percentile of amniotic fluid index. In addition, the amniotic fluid glucose of normal range (ie, > 15 mg/dL) may be falsely normal in the face of maternal hyperglycemia. For example, patient No. 35 with gestational diabetes treated with insulin (A2GDM), preterm rupture of membranes, and chorioamnionitis at 33 weeks' gestation had an amniotic fluid glucose value of 61 mg/dL with a serum glucose of 216 mg/dL.
Limitations of the study included an inconsistent amount of time between the amniocentesis and procurement of the maternal finger stick glucose values (although, at most, the finger stick glucose was obtained 1 hour after the amniocentesis). In addition, there was no standardization between oral intake and time of obtaining our glucose values. Finally, our study included women carrying multiple fetuses; only the twin of interest (eg, presenting and preterm rupture of membranes) underwent amniocentesis, yet no research has been conclusive on amniotic fluid concentration and distribution between the fetuses. There is a potential for skewed amniotic fluid glucose values in multiple gestation pregnancies, however, in the 10 participants of our study with multiple gestations, we observed no difference. In spite of these limitations, our study extends and confirms previous research findings. Further research is needed to establish acceptable levels of maternal serum glucose and amniotic fluid glucose to decrease the potential for false-negative amniotic fluid glucose values in patients with chorioamnionitis.
References
- . Amniotic fluid glucose values in normal and abnormal pregnancies. Obstet Gynecol. 1985;65:333–339
- . Maternal, fetal, and amniotic fluid levels of glucose, insulin, and growth hormone. Obstet Gynecol. 1973;41:323–331
- . Correlation between amniotic fluid glucose concentration and amniotic fluid volume in pregnancy complicated by diabetes. Obstet Gynecol. 2000;182:901–904
- . Levels of amniotic fluid insulin and profiles of maternal blood glucose in pregnant women with diabetes type-1. Early Hum Dev. 1997;49:97–105
- Accuracy of Roche Accu-chek inform whole blood capillary, arterial, and venous glucose values in patients receiving intensive intravenous insulin therapy after cardiac surgery. Am J Clin Pathol. 2007;127:919–926
- The diagnostic and prognostic value of amniotic fluid white blood cell count, glucose, interleukin-6, and gram stain in patients with preterm labor and intact membranes. Am J Obstet Gynecol. 1993;169:839–851
Supported in full by the Good Samaritan Hospital Medical Education Research Fund.
PII: S0002-9378(08)02069-3
doi:10.1016/j.ajog.2008.10.046
© 2009 Mosby, Inc. All rights reserved.
Volume 200, Issue 5 , Pages e43-e44, May 2009
