EAL

VN: Micronutrients in Pregnancy (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine if maternal calcium intakes and circulating micronutrients (red cell folate, plasma ferritin, vitamin B12 and vitamin C), during pregnancy, are related to the bone mass in their offspring.

Inclusion Criteria:

Subjects were from the Pune Maternal Nutrition Study
Women from six rural villages (total population 35,000) were recruited
Initially, 2,675 women were eligible for the study: 2,466 agreed to participate and 1,102 became pregnant
Sonography completed at 15-18 weeks' gestation, in order to confirm pregnancy
After exclusions, 797 pregnant women were enrolled in study between June 1994 and April 1996
Following national policy guidelines, all pregnant women enrolled in study were provided 100 tablets of iron (60mg) and folic acid (500 micrograms) at 18 weeks' gestation.

Exclusion Criteria:

Women who experienced abortions
Major fetal anomalies detected on ultrasound
Multiple pregnancies
Terminations of pregnancy
Pregnancies detected later than 21 weeks.

Description of Study Protocol:

Recruitment

Subjects were from the Pune Maternal Nutrition Study
Women were from six rural villages (total population 35,000) were recruited
Initially, 2,675 women were eligible for the study: 2,466 agreed to participate and 1,102 became pregnant
After exclusions, 797 pregnant women were enrolled in study between June 1994 and April 1996.

Design

Anthropometry measurements, measured pre-pregnancy:

Weight
Height
Skinfold measures (biceps, triceps, subscapular and suprailiiac skinfold thickness)
Fat mass was calculated
Height of husband also noted.

Dietary intakes (between 18-24 weeks' gestation):

24-hour food recall; estimated energy, protein, carbohydrate and fats
Food frequency questionnaire of 111 foods in 17 categories on an eight-point scale
Estimated calcium intakes from the food frequency questionnaire.

Physical activitity levels, determined from a questionnaire

Biochemical (maternal) fasting measures (between 18-24 weeks' gestation):

Erythrocyte folate
Plasma ferritin
Vitamin B12
Vitamin C
Merhylmalonic acid
Homocysteine.

Measurements of newborns:

Birth weight
Placental weight
Crown-heel length.

At six years' follow-up of children:

Weight
Height
Examined for rickets.

DXA scans on both parents and children (six years post-natally)

Bone mineral content (BMC) determined
Bone mineral density (BMD) determined.

Statistical Analysis

Pearson correlation coefficients used to assess associations between potential determinants and DXA measurements
Multiple linear and logistic regression and ANOVA models were used to assess whether associations were independent of potential confounding factors.

Data Collection Summary:

Timing of Measurements

Maternal pre-pregnancy anthropometrics
At 18-24 weeks' gestation:

Dietary intakes
Physical workload
Biochemical indices.

At birth:

Newborns' anthropometrics.

At six years post-natal:

DXA tests on parents and children.

Dependent Variables

Variable One: Bone mineral density
Variable Two: Bone mineral content.

Independent Variables

Maternal diet
Anthropometrics
Biochemical indices.

Description of Actual Data Sample:

Initial N

2,466 women agreed to participate in the study
1,102 women became pregnant
After exclusion, 797 women enrolled in study
770 (12 had aborted, 14 had late terminations, one died)
762 live births (eight were still births), which formed the sample for the study.

Attrition (Final N)

695 children
39 had died at six years' follow-up
Four had no parental data.

Age

Median age: 6.2 years; 53% were boys, 47% were girls.

Ethnicity

Population from rural India.

Location

From rural India.

Summary of Results:

Children

Standard deviation scores
- Mean weight
  - Boys: -2.16
  - Girls: -2.32
- Mean height
  - Boys: -1.24
  - Girls: -1.37
- Mean body mass index
  - Boys: -2.06
  - Girls: -2.12
Children’s age, socioeconomic status, weight and height were positively related to all bone outcomes (P<0.01 for all)
The children’s birth weight, birth length and placental weight were positively associated with all bone outcomes (P<0.001 for all)
There were no differences between children born pre-term and those born full-term
Children who were exclusively breast fed for a longer duration had lower spine bone mineral density.

Mother’s Diet

Mother’s energy, protein and calcium intakes were low, compared with Indian Council of Medical Research recommended daily allowance for pregnant women
Median intakes in Pune (at 18 weeks and 28 weeks):
- 1,726kcal; 1,637kcal
- 45g protein; 42g protein
- 274mg calcium; 268mg calcium.
One-third of women never ate any meat, fish or eggs. A further quarter consumed them less than once a week.
Higher socioeconomic status was associated with higher intakes of milk and calcium (P<0.001 for both).

Mother’s Data and Bone Outcomes

More than 60% of women had low vitamin B12 concentrations (<150pmol per L). Approximately 50% of the women had low ferritin status (<12ng per ml) and 66% had low vitamin C concentrations (<23micromol per L). Only one woman had low folate status (<283nmol per L).
The following maternal nutritional variables were positively related to bone outcomes in the children
- Pre-pregnant fat mass
- Frequency of intake of milk, milk products, pulses, fruit, all calcium-rich foods at 18 and 28 weeks.
Maternal parity, tobacco use and physical workload score at 28 weeks were negatively related to the children’s bone outcomes
Maternal energy, protein, fat and carbohydrate intakes, plasma ferritin, plasma vitamin C, plasma vitamin B12, MMA and tHcy concentrations were unrelated to bone outcomes in the children
A total of 419 mothers had at least one child since the birth of the study child. All maternal bone outcomes were positively related to the interval and inversely related to the number of children born since the birth of the last child (P<0.01 for both).

Other Data

In Multiple Regression Analysis, larger parental bone mineral content (both parents), lower maternal parity, higher maternal intakes of milk and milk products at 28 weeks gestation and longer birth length independently predicted higher total body or spine bone mineral content in the child
Both parents’ bone mineral density, maternal milk and milk product intakes at 28 weeks and maternal folate status at 28 weeks were independent predictors of the child’s total or spine bone minieral density
Parents’ heights and DXA measurements were positively correlated with bone outcomes in the children.

Author Conclusion:

Modifiable maternal nutritional factors may influence bone health in the offspring
Fathers play a role in determining their child's bone mass, possibly through genetic mechanisms or through shared environment.

Funding Source:

Government:

Medical Research Council (UK)

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

Strengths

Large study
97% of follow up of offspring
Data supports importance of both genetic (maternal and paternal) and environmental factors, in relation to bone mineral acrual during childhood.

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)	Yes
	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)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	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
	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
	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.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	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
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
	1.3.	Were the target population and setting specified?	Yes
	2.	Was the selection of study subjects/patients free from bias?	???
2.	Was the selection of study subjects/patients free from bias?		???
	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?	???
	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?	???
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
	3.	Were study groups comparable?	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)	Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	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
	3.4.	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.)	???
	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.)	???
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	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.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	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
	4.2.	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
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
	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?	???
5.	Was blinding used to prevent introduction of bias?		???
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	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.)	???
	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.)	???
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	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
	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?	Yes
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	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
	6.2.	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?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	Yes
	6.6.	Were extra or unplanned treatments described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	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
	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.	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
	7.1.	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
	7.2.	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
	7.3.	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
	7.4.	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
	7.5.	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
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	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.	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
	8.1.	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
	8.2.	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
	8.3.	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
	8.4.	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)?	Yes
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	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
	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.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	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.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes