Therefore, participants are potentially of a higher socioeconomic status than the general population.
Members of the NCT are likely to have an interest in health, and may be more likely to actively seek health information than other pregnant women.
Participants who were recruited via the online questionnaire are likely to have had an interest in the research.
They also had to have Internet access to participate, which may mean they are not representative of the population.
In future research, recruitment via the NHS would be preferable.
Some participant characteristics differed from the wider pregnant population.