The number of weeks the fetus is in pelvis varies from person to person. Generally, the fetus will be in pelvis around 38 weeks of gestation for first-time mothers and a little later for menstruating mothers, mostly at the time of birth. At around 37 weeks of gestation, the doctor will make an initial assessment of whether the baby can be delivered vaginally based on the size of the fetus, the size of the pelvis, and how the fetus is pelvic. If the fetus is large in relation to the pelvis, it will not be easy to enter the pelvis and deliver vaginally. If the pelvis is normal in size and the fetus generally weighs no more than 4500g, it can be delivered vaginally after a full assessment by the obstetrician. In addition, fetuses over 4000g should not be delivered vaginally for too long, preferably no longer than 24 hours. If the fetus is spontaneously delivered around 38 weeks of gestation, the chance of vaginal trial of labor is higher, and most of the fetuses will be delivered spontaneously around 40 weeks of gestation.