As is usually the case, there are several reasons:
• Mother's build - as a rule, the slimmer the woman, the earlier pregnancy becomes noticeable;
• Elasticity of the abdominal wall muscles - a trained abs stretches worse, because of this, some athletic mothers begin to look pregnant later;
• Posterior flexion of the uterus is a physiological feature in which the uterus is positioned slightly differently than most - tilted back toward the rectum rather than forward toward the abdominal wall. Because of this, its increase becomes noticeable later;
• Twins - a woman carrying twins will, of course, have a larger belly than a woman pregnant with one baby, so it will begin to visually increase earlier.