- Click here for explanation of classification scheme.

To investigate the maternal demographic and metabolic factors contributing to the growth of fetal and fat body mass in women whose degree of glucose intolerance is less than that defining gestational diabetes in comparison with women with normal glucose metabolism.

 

• Caucasian
• Singleton pregnancies without congenital malformations
• Gestational age confirmed by first trimester ultrasound
• Absence of gestational diabetes based on the criteria of Carpenter and Coustan
• Two or more previous deliveries
• Pregestational BMI between 19 and 25 kg/m² 
• Absence of tobacco use
• Absence of previous gestational diabetes
• The study protocol was approved by the hospital institutional review board and written consent was obtained from each subject before participation in the study protocol.

• On the basis of GCT results, the 189 selected women were separated into 2 groups. Group 1 comprised 66 women with an abnormal GCT value (plasma glucose level > 135 mg/dL after 1 h) followed by negative 100-g GTT. Group 2 comprised 123 women with a normal GCT value.

   

Among the 39 women excluded, 25 decided to discontinue the study protocol, 5 did not deliver at the clinic, and 9 had spontaneous preterm delivery.

 

Recruitment 

In the period between January 1999 and December 2001, a population of pregnant women was screened for gestational diabetes between the 24^th and 28^th week of pregnancy with a 50-g, 1-h oral glucose challenge test (GCT) at the Perinatal Medicine Unit of the University of Florence.

Design Prospective Cohort

Blinding used The sonographers did not know to which group the women belonged.

Intervention:  not applicable  

Statistical Analysis 

• Continuous variables were compared with either Student’s t or Mann-Whitney U test.
• Categorical variables were tested with either X² or Fisher’s exact test.
• Multivariate logistic regression analysis established best-fit equations for fetal sonographic measurements of fat and lean body mass. A P <0.05 was considered statistically significant.
• Statistical analysis was performed by Stata statistical software release 5.0 (Stata, College Station, TX)

Timing of Measurements

• Measurements were obtained before meals, 1 and 2 h after meals, and every 2 h in the afternoon and during the night.
• After each visit, an ultrasound scan was performed, and the 24-h capillary glucose profile obtained by the subjects at home were performed.

Dependent Variables

• GCT and glucose tolerance test (GTT) - plasma glucose determinations were performed in the clinical laboratory of the hospital with the glucose oxidase method, using an automated system (Aeroset; Abbott laboratories, Abbott Park, Il) with inter-and intra-assay coefficients of variation (CVs) of 0.8%.
• Following the GCT, subjects were seen 3-week intervals in the period between 24 and 38 weeks.
• Women were asked to have three main meals at 8:00 A.M, noon, and 8:00 P.M, and to perform a 24-h glucose profile on the day preceding the ultrasound scan using a memory based reflectance meter (one Touch Profile; Lifescan, Milpitas, CA) with tested precision and accuracy (CV 3.0-4.0% and coefficient correlation 0.981, respectively) without modifying their lifestyle or following any dietary restriction. Measurements were obtained before meals, 1 and 2 h after meals, and every 2 h in the afternoon and during the night.
• After each visit, an ultrasound scan was performed, and the 24-h capillary glucose profile obtained by the subjects at home were performed. Ultrasound scans were performed using a commercially available, unmodified Teknos Esaote ultrasound machine (Easote, Genoa, Italy) with a 3.5 MHz transducer.
• Established techniques Bernstein and colleagues to measure the fat and lean body mass areas on axial ultrasound images of the mid-upper arm, the mid-upper leg, and the anterior abdominal wall thickness.
• At least two measurements (except for 4 observations for anterior abdominal wall thickness).  were made for each parameter at each observation. The mean value of each set of observations was used in the analysis. 848 Ultrasonographic examination and 848 24-h glucose profiles examination (mean number per subject 4.5, range 3-6 for both). Two operators performed the ultra sound examinations.
• The intra- and interobserver reproducibility of the measurements were tested in 20 different images. Precision was assessed as the coefficients of variation (CV) of previous measurements.

Body Location	Intraobserver CV (%)	Interobserver CV (%)
anterior abdominal wall thickness	2.2	5.2
subscapular thickness	2.5	6.1
lean body areas of the thigh	1.9	3.9
lean body areas of  the arm	2.3	5.6
fat body areas of thigh	2.9	5.9
fat body areas of arm	4.4	7.3

 Independent Variables

• Maternal age (years)
• Parity (n)
• Prepregnancy BMI (kg/m²)
• Maternal weight gain (kg)
• 1-h GCT value (mg/dL)
• Maternal blood glucose values (mg/dL)
• Preprandial
• 1-h postprandial
• 2-h postprandial
• Compliance (%)
• Gestational age at delivery (weeks)
• Neonatal sex (% boys)
• Birth weight (g)
• AGA
• LGA - large for gestational age when birth weight was  > 90^th  percentile based on standard growth of population
• SGA - small for gestational age when birth weight was < 10^th percentile based on standard growth of population.
• Ponderal index (units)- ratio between 100 times the weight in grams and the cube of length in centimeters.

Control Variables

 

 

Initial N: 228 subjects were recruited for the study. From the recruitment population, 189 women who had uneventful pregnancies, did not receive drugs known to affect glucose metabolism (e.g., steroids and Beta 2-sympathomimetics) through gestation, and delivered term (37-42 weeks completed) live-born infants.  

Attrition (final N):  as above

Age: See Table 1

Ethnicity: Caucasian

Other relevant demographics:

Anthropometrics

Location:The Department of Gynecology, Perinatology and Human Reproduction, University of Florence, Florence, Italy.

No differences were found in regard to the maternal characteristics between the study sub-group and the 39 excluded women.

Table 1 –Maternal and neonatal characteristics 

	Group 1	Group 2	P
n	66	123	-
Maternal age (years)	32.5(26-39)	33.5(26-39)	NS
Parity (n)	1(0-2)	1 (0-2)	NS
Prepregnancy BMI (kg/m2 )	22.1 (19.8-25.3)	22.7 (19-25)	NS
Maternal weight gain (kg)	11.1 (8-14)	11.5 (9-5)	NS
1-h GCT value (mg/dl)	156.3+ 19.1	112.3 + 19.4	<0.0001
Maternal blood glucose values(mg/dl)	-	-	-
Preprandial	76.9+ 11.12	61.3 +13.4	<0.003
1-h postprandial	120.9 +  12.8	97.5 + 11.2	<0.001
2-h postprandial	100.5 + 10.8	86.2 +11.7	<0.002
Compliance (%)*	94.3 + 2.3	93.6 + 2.6	NS
Gestational age at delivery (weeks)	39.2 + 1.6	39.8 + 1.4	NS
Neonatal sex (% boys)	34(51.5)	61(49.6)	NS
Birth weight (g)	3,561.8 + 351.3	3,382.2+ 348.2	<0.04
AGA	47(71.2)	104(84.6)	<0.04
LGA	16(24.3)	10(8.1)	<0.004
SGA	3(4.5)	9(7.3)	NS
Ponderal index (units)	2.71 + 0.21	2.53 + 0.12	<0.01

Data are median (range), means + SD, or n (%). *Patient compliance with self-monitoring of blood glucose was defined as the percentage of the 30 glucose measurements prescribed by the protocol during the 4 weeks before delivery that were actually performed . AGA, appropriate for gestational age; LGA, large for gestational age; SGA, small for gestational age.

The proportions of variance for which each of the independent variables (fetal body composition) were responsible is shown in Table 2.

Table 2 – Stepwise, regression analysis: factors correlating with fetal body composition

Dependent and independent variables	R2	Delta R2
-	-	-
Lean body mass	-	-
Head Circumference	-	-
Gestational age	0.70	-
(Gestational age) 2	0.87	0.17
Neonatal sex	0.92	0.05
Femur length	-	-
Gestational age	0.90	-
(Gestational age) 2	0.95	0.05
Mid-upper arm central area	-	-
Gestational age	0.65	-
(Gestational age) 2	0.70	0.05
Neonatal sex	0.77	0.07
Mid-thigh central area	-	-
Gestational age	0.60	-
(Gestational age) 2	0.73	0.13
Neonatal sex	0.78	0.05
2-h postprandial	0.82	0.04
Fat body mass	-	-
Anterior abdominal thickness	-	-
Group	0.48	-
(Gestational age) 2	0.52	0.04
1-h postprandial	0.67	0.15
Subscapular thickness	-	-
Group	0.40	-
(Gestational age) 2	0.44	0.04
1-h postprandial	0.55	0.11
Prepregnancy BMI	0.58	0.03
Mid-upper arm area	-	-
Group	0.45	-
(Gestational age) 2	0.48	0.03
1-h postprandial	0.60	0.12
2-h postprandial	0.62	0.02
Mid-thigh area	-	-
Group	0.45	-
(Gestational age) 2	0.49	0.04
1-h postprandial	0.61	0.05
2-h postprandial	0.64	0.03

Other Findings

• With respect to all parameters used to evaluate fetal lean body mass, no differences were observed between groups 1 and 2.
• The factors that were significantly associated head circumference were gestational age and sex (male)
• Gestational age was the only independently associated factor for femur length.
• For the central lean area of the mid-upper arm, independently associated factors were gestational age and sex.
• For the central lean areas of the mid-thigh, independently associated factors were gestational age, sex (male), and maternal 2-h postprandial glucose values.
• With respect to fetal fat body mass, the growth of the anterior abdominal wall thickness was significantly greater in group 1 than in group 2 from the 26^th week to the end of pregnancy. The factors that were significantly associated with this measurement were gestational age and maternal 1-h postprandial glucose values.
• The growth of the subscapular thickness was significantly greater in group 1 from the 26^th week to the end of pregnancy. The factors that were significantly and independently associated with this measurement were gestational age, maternal 1-h postprandial glucose values, and prepregnancy BMI.
• The growth of the mid-upper arm subcutaneous was significantly greater in group 1 from the 25^th week to the end of pregnancy. The factors that were significantly and independently associated with this measurement were gestational age and 1- and 2- h postprandial values.
• The growth of the mid-thigh subcutaneous area was significantly greater in group 1 from the 25^th week to the end of the pregnancy. The factors that were significantly and independently associayed with this measurement were gestational age, 1-h postprandial glucose values, and prepregnancy BMI.

 

• Study suggested the possibility of using sonographically determined fetal fat and lean body mass measurements as indicated by body composition.
• The assessment of the noted parameters, achievable in a noninvasive and reproducible fashion in pregnancies complicated by glucose intolerance, might enable the real-time detection of fetal overgrowth and disproportion, thus opening the possibility of exploring interventions that would limit fetal fat accretion, birth weight, and potential resulting morbidity.

Limitations:

• The results need confirmation and verification in glucose intolerant pregnant women to legitimize possible clinical use.
• The lack fat mass measurement in the neonate does not allow comparison between sonographic findings and those obtained postnatally.
• Standard curves lean and fat mass should be defined in a large normal population.

Analytical longitudinal surveys refer to what epidemiologists term prospective or cohort studies. A Cohort Study is a study in which patients who presently have a certain condition and/or receive a particular treatment are followed over time and compared with another group who are not affected by the condition under investigation. Studies of this kind provide a better opportunity than one time cross sectional studies to examine whether certain behaviors do in fact lead to (or cause) the disease.

The limitations and critique of the study, as stated by the authors appear to be very appropriate.