Background Weight gain during pregnancy depends on the maternal prepregnancy weight and height. Inappropriate weight gain has negative consequences, including the health care system and society because of its adverse birth outcomes.

Objective This study aimed to assess the magnitude and factors associated with gestational weight gain in Northwest Ethiopia.

Methods From September 2018 to June 2019, a community-based prospective follow-up study was conducted in Northwest Ethiopia. A total of 422 pregnant women were followed from conception to delivery and the data were collected using a multistage sampling technique. Stata 14 standard edition (SE) software was used for data analysis. Multinomial logistic regression was used to determine the relationship between dependent and independent variables. P value of ≤0.05 was used to determine statistical significance.

Results Majority of the participants had normal weight gain [65.12%, 95% confidence interval (CI): 60.08, 69.85]. Besides this, the rate of inadequate and overadequate weight gain was 21.53% (95% CI: 17.60, 26.05) and 13.35% (95% CI: 10.22, 17.25), respectively. Inadequate weight gain was linked to meal frequency [adjusted odd ratio (AOR): 0.52, 95% CI: 0.28, 0.97], targeted supplementary feeding program (TSFP) enrollment (AOR: 2.47; 95% CI: 1.35, 4.50), parity (AOR: 0.18; 95% CI: 0.05, 0.62), and alcohol consumption history (AOR: 0.47; 95% CI: 0.25, 0.88), whereas overadequate weight gain was associated with residency (AOR: 5.22; 95% CI: 2.43, 11.22) and TSFP status (AOR: 2.22; 95% CI: 1.08, 4.57).

Conclusions This study revealed a notable magnitude of both inadequate and overadequate weight gain. It found that good meal frequency, alcohol consumption, parity, and TSFP enrollment were associated with a reduced risk of inadequate weight gain during pregnancy. In addition, the study identified residence and TSFP enrollment as factors linked to overadequate weight gain during pregnancy.