1. It has something to do with the body of the expectant mother.
Some expectant mothers are very thin, and the fetus grows faster in the mother's stomach. If the head is bigger, the pressure on the expectant mother's abdomen will increase, causing the navel to protrude outward. If the expectant mother's navel is not well developed, the abdominal pressure will become greater, which will also lead to the navel protruding outward.
2. Related to fetal position
For expectant mothers with low fetal position, unless the fetus is very large, the navel generally does not protrude outward. Expectant mothers with high fetal position will generally have their navel protruding outwards, even those with small bellies will have their navel protruding outwards in the third trimester.
3. It is related to the pressure of the expectant mother's abdomen.
If the expectant mother's abdominal pressure suddenly increases, the navel will protrude outward, but after a period of rest, the navel will return to normal. Don't worry too much about this situation, generally it won't have any impact on the fetus.
4. It is related to the tightness of the expectant mother's skin.
Generally speaking, if the expectant mother's skin is tight, then there is generally no phenomenon that the navel protrudes outward. If the expectant mother's skin is slack, most of her navel will protrude after her stomach has obviously grown up for five months.
The above is the difference between a pregnant woman's navel protruding and concave. No matter whether the navel is concave or convex, as long as she is in good health and the fetus is normal, there is no need to be too nervous.