Associations of maternal pre-pregnancy obesity and excess pregnancy weight gains with adverse pregnancy outcomes and length of hospital stay

BACKGROUND It is relatively less known whether pre-pregnancy obesity and excess gestational weight gain (GWG) are associated with caesarean delivery, pregnancy complications, preterm birth, birth and placenta weights and increased length of postnatal hospital stay. METHODS We used a population-based cohort of 6632 women who gave birth in Brisbane, Australia, between 1981 and 1983. The independent associations of pre-pregnancy obesity, GWG and institute of medicine (IOM) categories of combined pre-pregnancy BMI and GWG with outcomes were examined using multivariable regression (for continuous outcomes) and multivariable multinomial regression (for categorical outcomes) models. RESULTS We found women who were obese prior to pregnancy and women who gained excess weight during pregnancy were at greater risk for a pregnancy complications (OR: 2.10; 1.74, 2.54; age adjusted model), caesarean section (OR 1.29; 1.09, 1.54), higher birth weight difference (206.45 gm; 178.82, 234.08) and greater placental weight difference (41.16 gm; 33.83, 48.49) and longer length of hospital stay. We also found that mothers who gained inadequate weight or were underweight before pregnancy were at greater risk of preterm birth (2.27; 1.71, 3.00), lower risk of pregnancy complications (0.58; 0.44, 0.77) and had lower birth (-190.63;-221.05,-160.20) and placental (-37.16; -45.23,-29.09) weights. Results indicate that all associations remain consistent after adjustment for a range of potential confounding factors with the exception of the association between pre-pregnancy obesity and hospital stay. CONCLUSIONS Pre-pregnancy obesity or excessive GWG are associated with greater risk of pregnancy complications, caesarean delivery and greater birth and placenta weight. Excess GWG is associated with a longer stay in hospital after delivery, independent of pre-pregnancy BMI, pregnancy complications and caesarean delivery. In addition to pre-pregnancy obesity, it is vital that clinical practice considers excess GWG as another indicator of adverse pregnancy outcomes.