RT Journal Article SR Electronic T1 PP.25 Interpregnancy Changes in Maternal Weight and Body Mass Index JF Archives of Disease in Childhood - Fetal and Neonatal Edition JO Arch Dis Child Fetal Neonatal Ed FD BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health SP A88 OP A89 DO 10.1136/archdischild-2013-303966.305 VO 98 IS Suppl 1 A1 Crosby, DA A1 Collins, M A1 O’Dwyer, V A1 O’Higgins, A A1 Farah, N A1 Turner, MJ YR 2013 UL http://fn.bmj.com/content/98/Suppl_1/A88.3.abstract AB Objective This longitudinal study examined changes in maternal weight and Body Mass Index (BMI) in the early pregnancy between a woman’s first and second baby. Methods We studied women more than 18 years old with a singleton pregnancy who delivered their first baby weighing ≥ 500 grammes in 2009 and who re-attended for antenatal care with a subsequent ongoing pregnancy before January 1st 2012. Maternal weight and height were measured accurately before 18 weeks gestation in both pregnancies and BMI was calculated. Results Of the 3284 primigravidas, the mean weight at the first antenatal visit was 66.4 kg (SD 12.7). The mean BMI was 24.5 kg/m2 (SD 4.6), and 11.3% (n = 370) were obese. Of these 3284 women, 1220(37.1%) re-attended for antenatal care before 2012 after confirmation of an ongoing pregnancy. Of the 1220 women who re-attended, 788 (64.6%) had gained weight (mean 4.6 kg SD 3.9), 402(33.0%) had lost weight (mean 3.0 kgs SD 2.9) and 30 (2.4%) had maintained their weight. As a result, 20.2% (n = 247) were now in a higher BMI category and 4.8% (n = 58) had become obese; 5.8% (n = 71) were in a lower BMI category and 1.2% (n = 15) were no longer obese. These early pregnancy weight changes were influenced by maternal age, but not by the duration of the interpregnancy interval. Conclusion As two thirds of women gain weight in the short-term after delivery of their first baby, we recommend that the advice women get before and during pregnancy needs to be reinforced postpartum.