Strengths and limitations
PRETERM BIRTH
A strength of our design was the narrow gestational age range for trial visits, which increased the homogeneity of the data by ensuring that participants were at the same physiological stages of pregnancy at the respective visits. Our trial adds to the knowledge of PROs and clinical outcome measures when comparing IV and oral iron treatment in pregnant women, which has not been described in most previous similar trials. An obvious limitation of our trial was the lack of blinding. It is possible that participants had different expectations of the different treatment types, which may have biased PROs, especially. However, effective and feasible blinding would have been challenging, as IV iron is a dark fluid and oral iron frequently leads to dark-coloured stools. Second, the use of generic questionnaires is a limitation. As there are no existing questionnaires validated for pregnant women that evaluate the burden of symptoms possibly related to ID and IDA, we chose generic questionnaires that seemed most appropriate. Another limitation was the lack of power to measure clinical outcomes such as low birth weight and preterm birth. However, a proper power to investigate the effect of treatment on such rare outcomes would have required an unrealistic number of participants to be randomised. Lastly, the diversity of the study population was limited as most women were white.