Background <p>Current recommendations for adequate gestational weight gain (GWG) are based on body mass index (BMI) classes proposed by the WHO. However, for Asian populations alternative BMI classifications have been suggested. This study aims to explore the associations between GWG and pregnancy outcomes using WHO, Asian and Indonesian BMI cutoffs.</p> Methods <p>A prospective longitudinal study was conducted in the Parepare district, Indonesia. Of 1216 pregnant women enrolled, 953 mother-child dyads had complete newborn data. BMI was categorized into: underweight, normal weight, overweight, and obesity according to WHO, Asian and Indonesian BMI cutoffs. IOM criteria were used to determine GWG adequacy. Adverse pregnancy outcomes were: small for gestational age, preterm birth and low birth weight. For all three BMI classifications, logistic regression analyses were performed to examine the association between GWG and pregnancy outcomes. Additionally, we conducted a goodness of fit test to compare the model performance for each BMI classification method.</p> Results <p>The prevalence of underweight was 11.4% regardless of BMI classification. The prevalence of overweight was 22.2%, 33.3%, and 11.8%, whereas the prevalence of obesity was 6.8%, 14.4%, and 17.3% using the WHO, Asian and Indonesian cutoffs, respectively. Across all BMI classifications, a considerable proportion of women who were classified as underweight (&gt; 70%) or normal weight (&gt; 69%) exhibited inadequate GWG. The Asian BMI classification had the highest proportion of excessive GWG (15.2%).</p> Conclusion <p>Gestational weight gain classes based on Asian BMI cutoffs corresponded better with adverse pregnancy outcomes than WHO or Indonesian BMI cutoffs. We hypothesize that implementing the Asian BMI classification may better identify risks for adverse pregnancy outcomes, enabling more accurate and timely interventions targeting (pre)pregnancy to improve outcomes for mother and child.</p>