| 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 | Â | Study reported two sets of results, for calcium from food and from prenatal supplements. | Study in twins. |