When is it appropriate to start calculating weight gain after the first trimester?

Weight gain during pregnancy is a significant indicator of maternal and fetal health. The recommended practice is to begin monitoring weight gain after the first trimester, which generally starts at the end of week 12. Starting the assessment at this specific point allows healthcare providers to establish a baseline after initial rapid changes that occur in early pregnancy, when women frequently experience varying degrees of morning sickness and weight fluctuations.

From week 12 onwards, women usually stabilize and may begin to gain weight consistently, aligning with the expected growth of the fetus and corresponding increases in maternal blood volume, breast tissue, and fat stores. Thus, assessing weight gain commencing from week 12 provides a clear and standardized framework for evaluating whether the pregnancy is progressing healthily.