Research Needs in Pregnant and Lactating Populations
Identifying and studying additional biomarkers of energy and nutrient
intake will advance validation efforts and lead to a better understanding
of the biases and sources of measurement error in dietary assessment instruments
in pregnant or lactating populations. Currently very limited information
is available on systematic measurement error, including both group-specific
bias and person-specific bias in these populations for the 24HR (24-Hour
Recall), FR (Food
Record) or FFQ (Food
Frequency Questionnaire) instruments. Although difficult and expensive,
large-scale studies of free-living pregnant women at various stages of
pregnancy using biomarkers, such as the DLW (Doubly
Labeled Water) method for measurement of TEE (Total
Energy Expenditure), paired with the various dietary assessment instruments
would be helpful. Similar studies with lactating women at various postpartum
stages would be useful. Research is needed to identify other pregnancy
or lactation-specific laboratory indices for nutritional evaluation. Research
is also needed to identify sensitive, noninvasive, and specific biomarkers
of functional reproductive outcomes (12).
Yang and Erickson reviewed surveys of folic acid status in non-pregnant
or lactating women of reproductive age and have examined the relationship
of blood folate concentrations to reported supplement and food intake.
They found significant reporting error in supplement use. Similar studies
in pregnant or lactating women are needed (63).
Certainly the methods research priority recommendations from the "Future
Directions for the Integrated CSFII-NHANES" 2002 workshop (9;64)
can be applied to pregnant or lactating women. Among the recommendations
are:
- Determine ways to identify and remove bias associated
with under- and over-reporting of food, beverage, and supplement intake
in 24HR interviews;
- Further develop and pilot test propensity questionnaires
(frequency-type questionnaires) to augment information collected in 24HRs
and estimate the proportion of users of infrequently consumed foods;
- Develop and validate improved methods for assessing dietary
supplement use; and
- Determine the best way to assess severity of inadequacy
and excess nutrient intake (9;64).
In a longitudinal survey, the optimal timing and frequency of dietary assessment
in pregnant and lactating women should be examined. The impact of social
desirability bias, body-mass index, and maternal weight gain on self-reports
of food, beverage, and supplement intake at various stages of pregnancy
and lactation have not been well studied. Further work is needed on the
most appropriate instruments for low-literacy populations, various ethnic
groups, and adolescent pregnancies. Validation of automated or web-based
dietary assessment methods is needed.
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