GDM: Weight Management (2008)
To answer the following 2 questions:
- After adjusting for prepregnancy BMI and weight gain during pregnancy, do maternal and neonatal morbidity differ among women with gestational compared with pregestational DM?
- To what degree do maternal obesity and excess weight gain contribute to the development of adverse outcomes among women with DM during pregnancy?
- All consecutive women with DM and a singleton pregnancy who delivered at the hospital between May 1, 1993 and August 31, 1998. If a women delivered more than once during this time, her first pregnancy was selected.
- Women diagnosed with either pregestational DM (i.e. type 1 and type 2 DM) or gestational DM, according to estabalished criteria.
Recruitment
Since May 1993, data were collected on all women who delivered at the hospital, regardless of maternal health, mode of delivery, or perinatal outcome.
Design
Prospective cohort study.
Blinding used (if applicable)
Neither the nurses nor physicians in the study were blinded to the patients' DM subtype, past medical and obstetrical history, or fetal status.
Intervention (if applicable)
No active intervention.
Authors stated that dietary counselling and capillary blood sugar testing were typically offered to women diagnosed with GDM, with addition of insulin therapy for those whose 2-hr PC sugars remained >7.0-8.0 mmol/l.
Levels of glycemic control were not measured in this study.
Statistical Analysis
- Multiple logistic regression to examine the association between DM type and each study outcome adjusting for specific covariates, as defined a priori (see Control Variables).
- Baseline characteristics comparing between groups: 2-sample t-test for continuous variables or the chi-square test for categorical data. P<0.05 was set as the significance level.
Timing of Measurements
- All data were prospectively entered into an on-site computer by the attending nurse, generally within a few hours of delivery.
- To complete the data set, two authors reviewed the standard antenatal sheets of all women included in the study. Additional information on pre-pregnancy weight (kg), height (cm), and net weight gain during pregnancy, and calculated pre-pregnancy BMI were collected. The correct DM classification was also verified. If the antenatal records were not available through the hospital chart, then the primary care obstetrician or family physician was contacted for these data.
Dependent Variables
- For mothers:
- A diagnosis of shoulder dystocia
- A composite of either shoulder dystocia or cephalopelvic disproportion
- All-cause Caesarean section, as well as Caesarean delivery with and without labor
- A composite of either all-cause Caesarian or forceps delivery
- Development of a second, third or fourth degree vaginal tear
- Hypertensive disorders of pregnancy: Development of either gestational hypertension (HTN) or pre-eclampsia
- For baby:
- Admission to the NICU, regardless of cause or duration
- Large for gestational age birthweight (LGA: a birthweight > 2 SD above the 50th percentile weight for gestational age
- Preterm delivery before 32 or 37 weeks gestation
Independent Variables
- DM type: pregestational vs. gestational DM
Control Variables
Maternal covariates included:
- Maternal age (1 yr increments)
- Parity
- Pre-pregnancy BMI
- Net weight gain during pregnancy (5 kg increments)
- History of chronic HTN
- History of preterm delivery before 37 weeks
- History of neonatal death or still-birth
- History of previous Caesarian section or uterine surgery
- Fetal presentation (vertex vs. breech) was only included in the analyses of Cesarean delivery outcome.
In the analyses of neonatal outcome, the presence of placenta previa, gestational age at deliver and maternal receipt of betamethasone for fetal lung maturity were included solely in NICU admission.
Initial N: 624 (428 women with GDM; 196 women with pregestational DM and singleton pregnancies)
Attrition (final N): 624 - complete data were available on all women, with the exception of BMI, for which height was not measured in 67 (16%) women with GDM and in 21(11%) with pregestational DM
Age: GDM women = 33.1 yr; Pregestational DM women = 31.5 yr (p<0.001 between groups)
Ethnicity: No data
Other relevant demographics:
No significant difference in % primigravidae, prior C-section, prior preterm delivery, previous stillbirth or neonatal death, or mean neonatal birthweight at current delivery between GDM and pregestational DM women.
Anthropometrics
| GDM (n=428) | Pregestational DM (n=196) | |
|
BMI<20 BMI 20-24.9 BMI 25-29.9 BMI >= 30 |
33 (9%) 138 (38%) 106 (29%) 84 (23%) |
10 (6%) 80 (46%) 46 (16%) 39 (22%) |
Note: BMI data were unavailable in 67 (16%) women with GDM and in 21 (11%) with pregestational DM
Location: Canada
I. Rates and adjusted odds ratios (OR) for delivery and maternal health outcomes among women with pre-gestational and gestational diabetes mellitus
|
Maternal characteristic
|
Shoulder dystocia
|
All-cause Caesarian
|
AlI-cause Caesarian
|
Second, third or fourth
|
Hypertensive disorders
|
|||||
|
|
or cephalopelvic
|
delivery
|
or forceps delivery
|
degree vaginal tear
|
of pregnancy
|
|||||
|
|
disproportion
|
|
|
|
|
|||||
|
Rate (%) OR* (95% CI)
|
Rate (%) OR* (95% CI)
|
Rate (%) OR* (95% CI)
|
Rate (%) OR* (95% CI)
|
Rate(%) OR* (95% CI)
|
||||||
|
DM type
|
|
|
|
|
|
|
|
|
|
|
|
Gestational
|
14.2
|
1
|
34.1
|
1
|
40.6
|
1
|
23.5
|
1
|
8.9
|
1
|
|
Pregestational
|
25.5
|
2.2
(1.3-3.6)
|
60.2
|
3.6
(2.3-5.6)
|
66.3
|
3.3
(2.1-5.1)
|
18.4
|
0.8
(0.5-1.3)
|
20.4
|
3.0
(1.7-5.4)
|
|
Pre-pregnancy
|
|
|
|
|
|
|
|
|
|
|
|
20.0
|
14.0
|
1
|
30.2
|
1
|
41.9
|
1
|
25.6
|
1
|
4.6
|
1
|
|
20.0-24.9
|
21.1
|
1.5
(0.6-3.8)
|
39.0
|
1.2
(0.5-2.8)
|
45.4
|
0.9
(0.4-2.0)
|
21
|
0.7
(0.3-1.6)
|
10.6
|
1.8
(0.4-8.1)
|
|
25.0-29.9
|
16.4
|
1.3
(0.5-3.5)
|
43.4
|
1.3
(0.6-3.3)
|
50.7
|
1.1
(0.5-2.5)
|
27.0
|
1.3
(0.6-2.9)
|
13.2
|
2.6
(0.6-11.8)
|
|
>= 30
|
15.4
|
1.2
(0.4-3.4)
|
55.3
|
3.5
(1.4-8.6)
|
58.5
|
2.3
(1.0-5.4)
|
14.6
|
0.4
(0.2-1.1
|
17.1
|
4.1
(0.9-18.9)
|
|
Weight gain (5 kg increments)
|
-
|
1.1
(0.9-1.3)
|
-
|
1.2
(1.0-1.4)
|
-
|
1.2
(1.0-1.4)
|
-
|
0.9
(0.8-1.1)
|
-
|
1.4
(1.2-1.7)
|
*adjusted odds ratios for all control variables
II. Rates and adjusted odds ratios for neonatal outcomes among women with pregestational and gestational diabetes mellitus
|
Maternal characteristic
|
NICU admission
|
LGA
|
Preterm birth
|
Preterm birth
|
||||
|
|
|
|
< 32 wk
|
< 37 wk
|
||||
|
Rate (%) OR* (95% CI)
|
Rate (%) OR* (95% CI)
|
Rate (%) OR* (95% CI)
|
Rate (%) OR* (95% CI)
|
|||||
|
DM type
|
|
|
|
|
|
|
|
|
|
Gestational
|
45.8
|
1
|
15.9
|
1
|
4.7
|
1
|
19.2
|
1
|
|
Pregestational
|
83.7
|
4.0 (2.3-6.8)
|
37.2
|
3.5 (2.2-5.6)
|
7.1
|
2.1 (0.8-5.1)
|
43.4
|
3.8 (2.5-5.9)
|
|
Pre-pregnancy
|
|
|
|
|
|
|
|
|
|
20.0
|
39.5
|
1
|
9.3
|
1
|
4.6
|
1
|
7.0
|
1
|
|
20.0-24.9
|
54.1
|
1.2 (0.5-2.7)
|
24.8
|
2.5 (0.8-7.7)
|
3.2
|
0.6 (0.1-3.3)
|
28.0
|
5.0 (1.4-17.6)
|
|
25.0-29.9
|
61.8
|
1.9 (0.8-4.4)
|
24.3
|
2.6 (0.8-8.2)
|
4.6
|
0.9 (0.2-4.6)
|
28.3
|
5.5 (1.5-19.4)
|
|
>= 30
|
65.0
|
2.4 (1.0-5.9
|
26.0
|
3.3 (1.0-10.6)
|
6.5
|
0.8 (0.4-4.4)
|
27.6
|
5.1 (1.4-18.6)
|
|
Weight gain (5 kg increments)
|
-
|
1.2 (1.0-1.4)
|
-
|
1.3 (1.1-1.6)
|
-
|
0.9 (0.6-1.3)
|
-
|
1.0 (0.8-1.2)
|
*adjusted odds ratios for all control variables
Other findings:
There were 17 (2.7%) congenital defects detected at birth. The number of anomalies that may have resulted in a either spontaneous or therapeutic termination before birth was not available. Five (2.6%) anomalies were seen in the offspring of mothers with pregestational DM, of whom four had type 1 DM. The remaining 12 (2.8) congenital anomalies arose in the offspring of mothers with gestational DM.
The observation that pregestational DM confers a higher risk for obstetrical complications compared to GDM, independent of baseline weight and weight gain. However, this finding may be explained by the other risk factors that were not adjusted in the analyses.
In our population of women with DM, both pregestational and GDM, we found pre-pregnancy obesity to be independently and strongly associated with both LGA and birth before 37 weeks, while net weight gain during pregnancy had a more modest effect.
Two types of DM were compared: GDM vs. pregestational DM (type 1 and type 2).
This study was funded by the Physician's Services Incorporated Foundation, Toronto, Ontario.
There was a systematic review of all studies published between 1985 and May 2000 that included women with either GDM or pregestational DM, and provided data on both LGA and all-cause C-section delivery rate enclosed in this study (I did not present the results here).
Limitations:
- Levels of glycemic control were not measured in this study.
- Did not define or control for maternal ethnicity, which is a known risk factor for the development of both gestational and type 2 DM
- Care takers were not blinded to patients' characteristics
- Did not control for maternal co-morbidity, such as the presence of diabetic nephropathy.
Each of the above factors may have influenced the endocrinologists' and obstetrician' choice regarding timing and mode of delivery, and the prediatricians' decision to admit a newborn to the NICU.
|
Quality Criteria Checklist: Primary Research
|
|||
| Relevance Questions | |||
| 1. | Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) | N/A | |
| 2. | Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? | Yes | |
| 3. | Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? | Yes | |
| 4. | Is the intervention or procedure feasible? (NA for some epidemiological studies) | N/A | |
| Validity Questions | |||
| 1. | Was the research question clearly stated? | Yes | |
| 1.1. | Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? | Yes | |
| 1.2. | Was (were) the outcome(s) [dependent variable(s)] clearly indicated? | Yes | |
| 1.3. | Were the target population and setting specified? | Yes | |
| 2. | Was the selection of study subjects/patients free from bias? | Yes | |
| 2.1. | Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? | Yes | |
| 2.2. | Were criteria applied equally to all study groups? | Yes | |
| 2.3. | Were health, demographics, and other characteristics of subjects described? | Yes | |
| 2.4. | Were the subjects/patients a representative sample of the relevant population? | Yes | |
| 3. | Were study groups comparable? | Yes | |
| 3.1. | Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) | N/A | |
| 3.2. | Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? | Yes | |
| 3.3. | Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) | Yes | |
| 3.4. | If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? | Yes | |
| 3.5. | If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) | N/A | |
| 3.6. | If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? | N/A | |
| 4. | Was method of handling withdrawals described? | Yes | |
| 4.1. | Were follow-up methods described and the same for all groups? | Yes | |
| 4.2. | Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) | Yes | |
| 4.3. | Were all enrolled subjects/patients (in the original sample) accounted for? | Yes | |
| 4.4. | Were reasons for withdrawals similar across groups? | Yes | |
| 4.5. | If diagnostic test, was decision to perform reference test not dependent on results of test under study? | N/A | |
| 5. | Was blinding used to prevent introduction of bias? | No | |
| 5.1. | In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? | N/A | |
| 5.2. | Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) | No | |
| 5.3. | In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? | No | |
| 5.4. | In case control study, was case definition explicit and case ascertainment not influenced by exposure status? | N/A | |
| 5.5. | In diagnostic study, were test results blinded to patient history and other test results? | N/A | |
| 6. | Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? | No | |
| 6.1. | In RCT or other intervention trial, were protocols described for all regimens studied? | N/A | |
| 6.2. | In observational study, were interventions, study settings, and clinicians/provider described? | Yes | |
| 6.3. | Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? | ??? | |
| 6.4. | Was the amount of exposure and, if relevant, subject/patient compliance measured? | No | |
| 6.5. | Were co-interventions (e.g., ancillary treatments, other therapies) described? | No | |
| 6.6. | Were extra or unplanned treatments described? | No | |
| 6.7. | Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? | N/A | |
| 6.8. | In diagnostic study, were details of test administration and replication sufficient? | N/A | |
| 7. | Were outcomes clearly defined and the measurements valid and reliable? | Yes | |
| 7.1. | Were primary and secondary endpoints described and relevant to the question? | Yes | |
| 7.2. | Were nutrition measures appropriate to question and outcomes of concern? | Yes | |
| 7.3. | Was the period of follow-up long enough for important outcome(s) to occur? | Yes | |
| 7.4. | Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? | Yes | |
| 7.5. | Was the measurement of effect at an appropriate level of precision? | Yes | |
| 7.6. | Were other factors accounted for (measured) that could affect outcomes? | Yes | |
| 7.7. | Were the measurements conducted consistently across groups? | Yes | |
| 8. | Was the statistical analysis appropriate for the study design and type of outcome indicators? | Yes | |
| 8.1. | Were statistical analyses adequately described and the results reported appropriately? | Yes | |
| 8.2. | Were correct statistical tests used and assumptions of test not violated? | Yes | |
| 8.3. | Were statistics reported with levels of significance and/or confidence intervals? | Yes | |
| 8.4. | Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? | N/A | |
| 8.5. | Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? | No | |
| 8.6. | Was clinical significance as well as statistical significance reported? | Yes | |
| 8.7. | If negative findings, was a power calculation reported to address type 2 error? | N/A | |
| 9. | Are conclusions supported by results with biases and limitations taken into consideration? | Yes | |
| 9.1. | Is there a discussion of findings? | Yes | |
| 9.2. | Are biases and study limitations identified and discussed? | Yes | |
| 10. | Is bias due to study's funding or sponsorship unlikely? | Yes | |
| 10.1. | Were sources of funding and investigators' affiliations described? | Yes | |
| 10.2. | Was the study free from apparent conflict of interest? | Yes | |