|Methods||Randomised: method of randomisation is mentioned as central computer randomisation.|
Double blind: yes. It was mentioned that participants and study co-ordinator were both blinded. Data analyst was also blinded until end of data analysis.
Follow-up is described: done on weeks 20, 25, 32 and 4 weeks after expected delivery. 8.6% of participants in decaffeinated group and 4.9% of participants in the caffeinated group dropped out before giving birth.
|Participants||Overall 1207 pregnant women were randomised. 10 participants were excluded (due to erroneous serial number, participating twice and second pregnancy); 568 women were randomised to caffeinated instant coffee and 629 to decaffeinated instant coffee. Then, a total of 1153 women with a live born singleton were included in the analysis of birthweight and length of gestation. Of these, 8.60% (54/629) randomised to the decaffeinated group and 4.90% (28/568) randomised to the caffeinated group dropped out of the study before giving birth. |
Inclusion criteria: Danish-speaking women at less than 20 weeks' gestation who drank 3 cups of coffee per day.
Those with history of low birthweight baby (< 2500 g), preterm deliveries, kidney disease, epilepsy, diabetes, or metabolic disorders were excluded from the study.
|Interventions||Taking 3 cups of decaffeinated instant coffee (an average of 62 mg/day) versus the same quantity of caffeinated instant coffee.|
|Outcomes||Mean birthweight and length of gestational age were considered as the main outcomes. Length, head circumference, abdominal circumference, placenta weight, and Apgar score were secondary outcomes; these are not referenced in this review as they did not fit our objective.|
|Notes||This study was done between April 1996 and April 1998 in the Department of Obstetrics, Aarhus University Hospital, Denmark.|
|Risk of bias|
|Bias||Authors' judgement||Support for judgement|
|Random sequence generation (selection bias)||Low risk||Women randomised to receive decaffeinated or caffeinated coffee.|
|Allocation concealment (selection bias)||Low risk||Completed using computerised randomisation.|
|Blinding of participants and personnel (performance bias) |
|Low risk||Project co-ordinator and participants were blinded to the type of coffee.|
|Blinding of outcome assessment (detection bias) |
|Unclear risk||Not reported.|
|Incomplete outcome data (attrition bias) |
|Low risk||Only 8.60% (54/629) participants from the decaffeinated group and 4.90% (28/568) from the caffeinated group dropped out of the study.|
|Selective reporting (reporting bias)||Unclear risk||Not clear.|
|Other bias||Unclear risk||There are many other sources of dietary caffeine (tea, chocolate, etc) which were not measured in the study. Women in the decaffeinated coffee group could have increased their caffeine intake from other sources.|