Ectively, was 22.3 and 21.8 ,29 30 and 24 ,28 32.9 and 31.3 ,26 and 17.4 and 14.3 ,27 but 22.4 and 26.9 in another study.30 No differences in mobility rates were observed by type of birth defect among cases.29,33,34 In another study, infants born to movers had birth weights 47.5 g lower than Bayer 41-4109 site non-movers.38 Children whose mothers moved during pregnancy were 44 (12?5 ) more likely to be partially immunized and 42 (-15?34 ) more likely to be unimmunized than those who last moved >3 years before birth.39 Mothers’ health was assessed through studies of self-rated health and body mass index (BMI). The percentage of mothers who moved during pregnancy was 24.4 for BMI <18.5 (underweight), 18.7 for BMI 18.5?4.9 (normal), 12.6 for BMI 25?9.9 (overweight), and 17.1 for BMI 30 (obese).27 Other factors Several other factors were examined in relation to residential mobility during pregnancy in a few studies. Mothers who never breastfed were fpsyg.2015.00360 22 (7?0 ) more likely to move than those who breastfed 6 months.35 The likelihood of moving for mothers in urban environments compared with those in rural areas was 30.3 versus 29.1 26 and 12 versus 10 .31 Mobility rates for mothers living by the Texas border were 26 , with a rate of 31.1 for those not living by the border.26 Similar mobility was observed based on medication use during pregnancy (12 for users and non-users), exposure to pesticides or chemicals at work or home (yes 10 , no 13 ), and complications or illness during pregnancy (yes 8 , no 13 ).31 Renters were 3.12 (2.75?.55) times more likely to move than home owners.35 Of those in English-speaking homes, 19.29 moved compared with 16.88 for others.36 Mothers who were active during pregnancy moved at similar rates (11 ) as those with little to moderate activity (13 ).31 Similar rates of moving were observed based on season of birth.33,34 Impact of residential mobility on assessment of environmental exposures Some studies reported the distance between residences, as moves over larger distances are more likely to impact exposure assessments than shorter moves. Median distances in several studies were <10 km, although mean distances were often influenced by extreme observations. Hodgson et al.32 found a median distance of 1.4 km (mean 9.7 km) for moves between first prenatal visit and delivery for pregnancies resulting in birth defects. In a study of 141 subjects with birth defects and 591 subjects without, the median distance moved between conception and delivery was 6.9 km (mean 188.9 km, range 0.2?,346 km).28 On the basis of 912 cases with birth defects and 412 controls, median distance moved was 4.2 km (mean 16.7, range 0?81.8 km).27 Miller et al.29 found that for movers in the control group with known distances, 19.0 went <4.8 km, with 28.6 moving 4.8 to <13 km, 25.4 moving 13 to <39 km, and 27.0 moving 39 km. The percentage of movers that stayed within the same county was 52.1 .