- Click here for explanation of classification scheme.

This article tests the hypothesis that women with impaired glucose tolerance (IGT) have the same pregnancy outcomes as those of their counterparts with normal glucose tolerance.

 

• Women with a venous serum glucose level > 7.8 mmol/l
• Ethics approval was obtained from the Standing Committee for Research into Human at Monash University, and informed consent was obtained from all women who participated in the study.

 

• Women < 18 years of age
• Women with multiple pregnancies
• Women with maternal-fetal ABO incompatibility (titer >1:30) 
• Women diagnosed with prepregnancy diabetes
• Women under long-term medical treatment that may affect glucose metabolism
• Women who lived in rural districts or chose home delivery of baby. 

Recruitment details were not provided

Design Cohort

Blinding used (if applicable):  not applicable

Intervention : 48 women accepted a trial for diabetes care in pregnancy and received treatment; details provided in subsequent journal article.

Statistical Analysis 

• The Statistical Analysis System (SAS) was used to analyze the data.
• Wilcoxon’s rank sums test was used to test differences between two means of skewed and non-normal sampling distributions.
• The X² test was used to test differences between two proportions (rates) and the Fisher’s exact test for contingency tables (2x2) with a small expected cell count(>20% of cells<5%).
• Multiple logistic regression modeling was used to obtain estimates of odds ratio (OR) while controlling for conventional confounding factors as well as hospital levels to which women were admitted for delivery.

Timing of Measurements: All blood specimens obtained the laboratory staff were separated and determined within 1 h after sampling.

Dependent Variables

Diagnostic Criteria:

• The initial screening consisted of a 50-g 1-h glucose test and was carried out at 26-30 gestational weeks. Women with a serum glucose > 7.8 mmol/l were followed up with a 75-g 2-h oral glucose tolerance test. The World Health Organization’s diagnostic criteria for GDM was  used.
• All blood samples for the OGTT were processed at the Tianjin Institute for Women’s Health.
• A glucose oxidase (GOD) method was used to determine serum glucose levels
• Venous blood was collected in nonfluoride plain tubes (Dusheng Plastic Product Company, Cangzhou, China) and allowed clotting at room temperature.
• After clotting, serum was obtained by separation of the blood at 3,000 rpm/min.
• Serum was used for glucose determination.
• Glucose Liquid Reagent( Zhongsheng High-Tech Bioengineering Company, Bejing, China) and a semiautomatic biochemical analyzer were used to determine serum glucose.
• The wave-length was at 546 nm(Hg), and the reaction temperature was set at 37 degrees C.
• The readings of light absorption of the standard (A_standard )and the sample (A _sample) were recorded from the semiautomatic biochemical analyzer.
• Glucose concentration in the sample was calculated according to the following formula: C (mmol/l)= (A _sample/ A _{standard     X}     C _standard.
• The mean routine coefficient of variance (RC/V) was 3.14% (SD 0.82, range 2.04-4.37%).
• All participating ACBUs collected serum samples and used the GOD method.
• A standardized procedure was implemented in all participating ACBU laboratories.

Independent predictors for pregnancy outcome:

• EPH syndrome -IGT status(IGT vs. control)
• P-ROM -IGT status(IGT vs. control)
• Breech presentation-stature, IGT status(IGT vs. control)
• Preterm birth-prepregnancy BMI(kg/m²), -IGT status(IGT vs. control)
• Birth weight > 90^th percentile, IGT status (IGT vs. control); weight gain in pregnancy (kg); gestational weeks at delivery.

Pregnancy outcome:

• Preeclampsia and eclampsia
• Vertex presentation
• Caesarean delivery – Cephalopelvic disproportion, breech, foetal distress, postdates, others
• Birth trauma or dystocia
• Fetal male gender
• Low birth weight <2,500 g)
• Apgar score at 1 min < 7
• Hypoglycemia
• Pneumonia
• Perinatal death 

Independent Variables: collected from hospital medical records

• Age (years)
• Stature (cm) was measured at the initial screening using a standardized procedure and recorded to the nearest 0.1 cm.
• Pregravid body weight (kg)
• Pregravid BMI (kg/m²) was used to measure overweight and obesity.
• Household monthly income per person
• SBP at initial screening (mmHg)
• DBP at initial screening (mmHg)
• SBP at admission for delivery (mmHg)
• DBP at admission for delivery (mmHg)
• Body weight at admission for delivery (kg)
• Weight gain in pregnancy (kg) was obtained by subtracting body weight at delivery from the self-reported pregravid body weight
• Gestational weeks at delivery
• Parity before delivery (0,1)

Control Variables

Initial N: Of the 150 who completed data collection, 48 women accepted a trial for diabetes care in pregnancy and received treatment; 102 women opted for conventional care and received no treatment.

Attrition (final N):  as above

Age: See Table 1

Ethnicity: not mentioned

Other relevant demographics:  see Results

Anthropometrics

Location: Tianjin Antenatal Care Network, China

 

Women with IGT had a significantly higher SBP and DBP than those of NGT. Weight gain in pregnancy and gestational age at delivery were similar in the two groups (Table 1).

Table 1- Population characteristics between women with IGT and NGT

Characteristics	NGT (N=302)	IGT (N=102)	P*
Age (years)	26.5 + 2.95	28.0 + 3.68	0.0004
Stature (cm)	161.3 + 4.58	160.5 + 5.60	0.1018
Pregravid body weight (kg)	56.0 + 7.14	58.2 + 9.62	0.1260
Pregravid BMI(kg/m2)	21.5 + 2.57	22.6 + 3.49	0.0146
Household monthly income per person(RMB:Yuan)	645 +  479.5 (n=299)	590 + 272.3	0.7571
SBP at initial screening (mmHg)	106 + 8.8	107 + 11.6	0.7356
DBP at initial screening (mmHg)	70 + 6.8	69 + 8.1	0.6295
SBP at the admission for delivery (mmHg)	112 + 11.2 (n=298)	117 + 17.2 (n=101)	0.0259
DBP at the admission for delivery (mmHg)	74 +  8.6 (n=298)	77 + 10.6 (n=101)	0.0294
Body weight at admission for delivery(kg)	71.4 +  8.95 (n=290)	73.0 + 10.95 (n=83)	0.2215
Weight gain in pregnancy (kg)	15.4 +  5.60 (n=290)	15.4 + 6.48 (n=83)	0.6977
Gestational weeks at delivery	39.8 + 1.54	39.4 + 1.57	0.0936
Parity before delivery	-	-	0.5078¶
0	97.35% (294/302)	96.08%(98/102)	-
1	2.65%(8/302)	3.92% (4/102)	-

Data are means + SD values otherwise indicated. *Derived from Wilcoxon’s rank sums test; ¶ derived from Fisher’s exact test.

Women with IGT were more likely to develop edema proteinuria hypertension (EPH) syndrome than those of NGT (19.6 vs. 6.62%, P=0.0001).The significance level greatly reduced after controlling for maternal age, pregravid BMI, hospital levels and other confounding factors (OR 2.10; 95% CI 0.89-4.94, P=0.0889)(Table 2).

Women with IGT also had a significantly higher rate of premature rupture of membranes (P-ROM) than those with NGT (13.7 vs. 1.99%, P<0.0001)(Table 2).

Overall caesarean delivery rates were similar in the two groups, but the breech-specific caesarean delivery rate was significantly higher in the IGT group. Higher birth weight (> 90^th percentile or 4,000 g, 95^th percentile or 4,200 g) occurred more frequently in women with OGT than in the NGT group. The differences persisted after adjusting for maternal age, pregravid BMI, infant’s sex, EPH syndrome, weight gain, hospital levels, and gestational age at delivery (OR 2.42; 95% CI 1.07-5.46)(Table 2).

Table 2- Pregnancy outcomes in women with IGT and NGT

-	NGT (N=302)	IGT (N=102)	-
Variables	%(n)	%(n)	P§
-	-	-	-
EPH syndrome*	6.62(20)	19.6(20)	0.0001
Mild or moderate	6.62(20)	16.7(17)	0.0024
Preeclampsia and eclampsia	0.00(0)	2.94(3)	0.0157||
P-ROM	1.99(6)	13.7(14)	<0.0001
Breech presentation	3.31(10)	10.8(11)	0.0033
Vertex presentation	96.4(291)	89.2(91)	0.0060
Preterm birth (<37 gestational weeks)	1.32(4)	7.84(8)	0.0026||
Caesarean delivery	65.9(199)	73.5(75)	0.1535
Cephalopelvic disproportion	33.4(101)	23.5(24)	0.0611
Breech	3.64(11)	8.82(9)	0.0370
Fetal distress	13.6(41)	11.8(12)	0.6394
Postdates	1.96(2)	0.00(0)	0.0633||
Others	22.9(69)	46.1(47)	<0.0001
Birth trauma or dystocia	0.00(0)	0.00(0)	-
Fetal male gender	52.3(158)	54.9(56)	0.6512
Birthweight> 90th percentile	13.3(40)	21.6(22)	0.0437
Birthweight> 95th percentile	5.96(18)	12.8(13)	0.0260
Low birth weight(<2,500g)	1.66(5)	1.96(2)	1.0000||
Apgar score at  1min < 7	0.99(3)	1.96(2)	0.6039||
Hypoglycemia¶	0.33(1)	0.98(1)	0.4417||
Pneumonia	0.00(0)	1.96(2)	0.0633||
Perinatal death♦	0.66(2)	1.96(2)	0.2654||

*Mild EPH syndrome is SBP/DPB>173/12kaPa (130/90 mmHG), or with an increase in blood pressure of 4/2kPA (30/15 mmHG) compared with basal blood pressure, that may be accompanied with moderate proteinuria and edema. Moderate EPH syndrome: increase in blood pressure, SBP/DPB>21.3/14.6kaPa (160/110) proteinuria with +, or accompanied with edema or mild symptoms. Severe EPH syndrome includes pre-eclampsia and eclampsia; ¶capillary blood glucose level<1.7 mmol/L: ♦ fetal/neonatal death from 28 gestational weeks to 7 days after birth; § X² test.        || Fisher’s exact test.

Weight gain and gestational weeks at delivery were independent predictors of high birth weight (90^th percentile). Breech presentation was significantly more common in women with IGT than those of NGT (10.8 vs. 3.31%, P=0.0033)(Table 3)..

After controlling for age, stature, pregravid BMI, pregnancy weight gain, hospital levels, and EPH syndrome, women with IGT were 10.07 times (95% CI 2.90-34.93) more likely to have P-ROM than their normal counterparts (Table 3).

Table 3 Independent predictors for pregnancy outcomes 

Variables	OR	95% CI	P
EPH syndrome*	-	-	-
IGT status (IGT vs. control)	2.10	0.89-4.94	0.0889
P-ROM¶	-	-	-
IGT status (IGT vs. control)	10.07	2.90-34.93	0.0003
Breech presentation ¶	-	-	-
Stature (cm)	1.12	1.03-1.23	0.0128
IGT status (IGT vs. control)	3.47	1.11-10.84	0.0323
Preterm birth ¶	-	-	-
Prepregnancy BMI (kg/m2 )	1.28	1.06-1.55	0.0124
IGT status (IGT vs. control)	6.42	1.46-28.34	0.0140
Birth weight > 90th percentile ♦	-	-	-
IGT status (IGT vs. control)	2.42	1.07-5.46	0.0329
Weight gain in pregnancy (kg)	1.16	1.09-1.24	<0.0001
Gestational weeks at delivery	1.24	1.00-1.54	0.0498

* Controlling for age (years), household monthly income  per person (RMB: Yuan), educational attainment(1. junior high school or less; 2. senior high school; 3. college; 4. university), stature (cm), prepregnacy BMI (kg/m² ), weight gain in pregnancy(kg), parity, and hospital levels (secondary vs. tertiary); ¶ controlling for EPH syndrome and above factors except for parity; ♦ controlling for above all factors, plus gestational weeks at delivery, infant’s sex(1.male; 2.female), and parity.

Other Findings

 

 

• The presence of IGT in pregnancy is predictive of poor pregnancy outcomes.
• Women with IGT were at increased risk for premature rupture of membranes (odds ratio [OR] 10.07; 95% CI 2.90-34.93); preterm birth (6.42; 1.46-28.34); breech presentation (3.47; 1.11-10.84); and high birth weight (90^th percentile 4,000g) (2.42; 1.07-5.46); adjusting for maternal age, pregravid BMI, hospital levels, and other controlling factors.

Limitations:

• Technical, as well as logistic, difficulties were potential barriers to scientific data collection that is considered fundamental to future policy decisions.
• Despite careful planning in hospital selection to obtain a representative NGT sample, the researchers found that the sampling distribution for age, BMI, blood pressure(SBP and DBP), and gestational weeks at the initial screening for the 302 control subjects shifted to the right-hand side of the general obstetric population of Tianjin City. The bias appeared systematic and was in part removed through statistical adjustments.
• As a comparison group, a higher rather than a lower reading on age, BMI, blood pressure, and gestational weeks at the initial screening was likely to contribute to an underestimation of poor pregnancy outcomes that were reported.
• Missing medical records, in particular maternal body weight when admitted for delivery (IGT: 19 and NGT: 12), may also contribute to a reduced predictive power and further underestimate poor perinatal outcomes. 

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.