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Table 2 Characteristics of observational studies included in the review.

From: Effect of maternal calcium intake during pregnancy on children's blood pressure: A systematic review of the literature

 

McGarvey, 1990

Gillman, 2004

Morley, 2004

Country, region

Rhode Island, USA

Massachusetts, USA

Tasmania, Australia

Age at Follow-up

At birth – 1 month – 6 month – 12 month

6 month

9 years

Sample size

212 – 184 – 114 – 70

936

294

Outcome measures

Systolic and diastolic blood pressure

Systolic blood pressure

Systolic and diastolic blood pressure, insulin, fasting glucose, triacylglicerol, cholesterol (total, HDL and LDL)

Average maternal calcium intake during pregnancy (mg/day)

1712

Total:1494 first trimester (FT), 1330 second trimester (ST). From prenatal supplements: 264 (FT), 203 (ST). From food: 1230 (FT), 1128 (ST).

NA

Exposure measurement

Maternal prenatal diet assessed postpartum in hospital by a 116 item semi quantitative food frequency questionnaire.

Maternal diet assessment with a semi quantitative food frequency questionnaire validated in pregnancy during the first trimester and second trimester. Analysis stratified by calcium from food and calcium from prenatal supplements.

Mothers of all live born twins in Tasmania were approached soon after birth. They were asked whether they had taken any nutritional supplements during pregnancy.

Exposure categories, maternal calcium intake in mg

Quartiles (1380, 1722, 2048) and correlation coefficients

Quartiles (Q4 - Q1 = 424 mg) and linear regression

Maternal calcium supplements during pregnancy (yes/no). Calcium content of supplements not stated.

Blinding of exposure status and ascertainment of outcome.

Unknown

Unknown

Unknown

Lost to follow-up or invalid exclusions

Total eligible population not stated. 212 mothers with prenatal dietary data included. Lost to follow-up by age at follow-up (%): 0 13 46 67

2128 total population. 462 missing maternal diet assessment, 232 did not consent, 381 did not attend follow-up visits, 77 outcome missing, 39 missing covariates.

Total eligible population not stated. 463 twin children recruited. 11had co-twin not available for recruitment. 23 pairs left Tasmania. 14 pairs could not be traced and 42 declined to participate.

Adjustment

Cuff size, observer, sleep/activity status. Age in days (At birth), body weight (at 6 and 12 month). Maternal race, parents education and occupation. Dietary potassium and magnesium

Energy intake, BP measurement conditions (cuff size, infant position, appendage used, machine model, infant state, clinic site)

Maternal age and education, twin pair birth order (in family), child age at assessment and sex. Study in twins.

  

Maternal race, education, number of previous pregnancies, marital status, pregnancy body mass index and third trimester systolic blood pressure. Infant age and sex.

 

Comments

 

Study reported two sets of results, for calcium from food and from prenatal supplements.

Study in twins.