There is no direct relationship between swollen feet at 39 weeks and whether or not you are in labor. You should only consider that you are in labor if there are signs of labor such as redness, irregular contractions, and water breaking.
Swollen feet at 39 weeks may be caused by physiological factors, or pathological factors, such as hypertensive syndrome of pregnancy, pre-eclampsia, nephritis and other factors.
A large part of the edema in late pregnancy is caused by physiological factors. The enlarged uterus compresses the inferior vena cava, leading to obstruction of venous return, coupled with physiological hypoproteinemia during pregnancy, which in turn produces physiological edema. This kind of edema is generally more limited, you can rest properly, pay attention to observation, strengthen the protein food intake.
If the edema gradually spreads to the legs and thighs, then we should be alert to whether it is caused by disease factors, and we need to regularly test blood pressure, urine protein, liver and kidney function.
Regular checkups are needed during pregnancy, and if you feel unwell, seek medical attention.