Figure 1

Percentage of women moving house during pregnancy by year of delivery. The solid line up to 1999 shows mobility when cases with a missing address at delivery are excluded from the analysis; the dotted lines show mobility under the assumption that cases with missing address at delivery had not moved (lower line), or that cases with missing address at delivery were twice as likely to have moved (upper line). From 1999, due to changes in data entry, cases with the same address at booking and delivery were a) assumed not to have moved or b) re-classified to represent missing data (47%) and excluded from the analysis.