Table 1 Study characteristics for the NMS (1995–2018)
Year of survey | 1995 | 2006 | 2010 | 2014 | 2018 |
|---|---|---|---|---|---|
Sample source | ONS birth registrations | ONS birth registrations | ONS birth registrations | ONS birth registrations | ONS birth registrations |
Number of women sampled | 3570 | 4800 | 10,000 | 10,002 | 16,000 |
Region | England and Wales | England | England | England | England |
Period of birth | June–July 1995 | March 2006 | October–November 2009 | January 2014 | October 2018 |
Baby age at recruitment | 4 months | 3 months | 3 months | 3 months | 6 months |
Time of initial mail out | November | June | January | April | April |
Modes of response available | Postal | Postal Telephone (interpretation service) | Postal Telephone (interpretation service) Online | Postal Telephone (interpretation service) Online | Postal Telephone (interpretation service) Online |
Incentive | None | None | None | None | Prize draw for £500 gift voucher |
Number or reminders | 0 | 2 | 3 | 3 | 2a |
Timing of reminders (from initial mail-out) | N/A | + 2 weeks: reminder letter + 4 weeks: reminder questionnaire | + 2 weeks: reminder letter + 4 weeks: reminder questionnaire + 8 weeks: reminder letter | + 2 weeks: reminder letter + 4 weeks: reminder questionnaire + 8 weeks: reminder letter | + 3 weeks: reminder questionnaire + 7 weeks: reminder questionnaire |
Length of questionnaire | 44 pages | 28 pages | 28 pages | 28 pages | 16 pages |