Yu 2008.
| Methods | Randomised controlled trial; 4 x 3 block design with randomisation at individual level. | |
| Participants | 180 pregnant women (45 Indian Asians, 45 Middle Eastern, 45 Black and 45 Caucasian) women at 27 weeks' gestation attending the routine antenatal clinic at St Mary’s Hospital, London, the UK (latitude: 51°30'N north of tropic of Cancer). Exclusion criteria: pre‐existing sarcoidosis, osteomalacia, renal dysfunction and tuberculosis. Pre‐gestational BMI and skin pigmentation (in addition to ethnicity) not reported. The study took place between April 2007 and November 2007. As well, a follow‐up trial of the infants of these trial participants. All of the offspring of the 180 mothers recruited in this trial were eligible and were invited to participate in a follow‐up study when their children were 3 years of age. | |
| Interventions | Participants were randomised in blocks of 15 within each of the 4 ethnic groups to 3 groups; Group 1 (n = 60) received a daily dose of vitamin D (ergocalciferol D2) at 800 IU; Group 2 (n = 60) received a one dose of 200,000 IU of calciferol; Group 3 (n = 60) received no treatment and served as controls. All groups received the intervention for 13 weeks, from start of supplementation to term. Data from groups 1 and 2 were collapsed for this analysis. Health worker cadre: each woman collected her tablets directly from the hospital pharmacy department or her local pharmacy. |
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| Outcomes | Maternal: maternal and cord 25‐hydroxyvitamin D levels at delivery, maternal PTH and corrected calcium levels at delivery, adverse events. Infant: small‐for‐gestational age was defined as birthweight less than the 10th percentile after adjustments for gestation at delivery, infant sex, maternal ethnicity, parity, height and weight. Wheezing episode in the first 3 years of life, measured at 36 to 48 months, use of inhaled bronchodilators in the last 12 months, doctor‐diagnosed rhinitis, any wheezing episode in the preceding 12 months, doctor‐diagnosed asthma, doctor‐diagnosed eczema, doctor‐diagnosed food allergy, positive skin prick test responses, 25‐hydroxyvitamin D levels, bronchodilator responsiveness, exhaled nitric oxide level (in parts per billion), nasal secretions for inflammatory mediators, pulmonary airflow resistance and reactance at a range of frequencies using impulse oscillometry, total number of all wheezing episodes since birth and total number of upper and lower respiratory tract infections since birth, at 36 to 48 months. Laboratory method used for assessment of vitamin D concentrations: not specified. |
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| Notes | Women who did not speak English were only included if a health advocate was able to interpret and a leaflet was provided in their language;
Source of funding: this study was funded by a research grant from the Institute of Obstetrics and Gynaecology Trust, Wolfson and Weston Research Centre for Family Health, Imperial College, Du Cane Road, Hammersmith Hospital, London W12 0NN, UK. Dates of the study and location: April 2007 to November 2007, London, UK. Declarations of interest among primary researchers (or state where this information is not reported by the trial authors): none declared. |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Computer‐generated random number lists were drawn up by an independent researcher, with randomisation in blocks of 15. |
| Allocation concealment (selection bias) | Low risk | The research staff allocating participants used the next available number on entry to the trial, and each woman collected her tablets directly from the hospital pharmacy department or her local pharmacy. |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Study personnel and participants were not blinded to treatment assignment. |
| Blinding of outcome assessment (detection bias) All outcomes | High risk | Study personnel was not blinded to treatment assignment. |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | Only 1 loss to follow‐up on group 3. |
| Selective reporting (reporting bias) | Unclear risk | There is insufficient information to permit judgement. |
| Other bias | Unclear risk | Women were randomised within each ethnic group. It is not clear if the ethnicity can be clearly established as it was self reported. Women who did not speak English were included only if a health advocate was able to interpret and a leaflet was provided in their language (English, Arabic, Bengali and Farsi) although the ability to read was not clearly established. |
β‐hCG: beta human chorionic gonadotropin BMI: body mass index CHW: community health workers ELISA: enzyme‐linked immunosorbent assay GDM: gestational diabetes mellitus GSH: glutathione HDL: high‐density lipoprotein IGF‐I: insulin‐like growth factor IU: international units IUFD: intrauterine fetal death LBW: low birthweight LDL: low‐density lipoprotein mcg: microgram PA: physical activity PTH: parathyroid hormone 25 (OH)D: 25‐hydroxycholecalciferol