The most natural way to deliver a baby is vaginally. With the advancement of medicine, doctors may recommend cesarean section for certain life-threatening pregnancies, but it does not mean that cesarean section is the shortcut to delivery that the medical profession promotes. Vaginal delivery has always been advocated in both foreign and domestic perinatal medicine, and cesarean delivery without medical indications should be eliminated. Do you know what the four major factors are that determine your labor? They include labor force (contractions), birth canal (pelvis), fetal size, and psychological factors. The purpose of perinatal care is to detect any abnormalities in these factors and to manage and improve them within the limits allowed. At 36-37 weeks of gestation, you will know the best way to deliver your baby. Usually, at 36-37 weeks of gestation, your health care provider will tell you the best way to deliver your baby, because by this time, the fetus is almost mature, the weight is relatively close to the birth weight, the pelvis has been measured, and after almost 9 months of care, your doctor will be able to adequately evaluate your physical condition to tolerate a vaginal delivery. At the same time, the good results of your health care will help you not to be too anxious about the pregnancy and delivery. It is time to wait quietly for the signal of your baby’s birth. Pelvic measurements to understand the condition of your birth canal During the middle and late stages of pregnancy, your doctor will know the shape and size of your pelvis, measured both externally and internally, the latter being more accurate than the former, but usually a combination of external and internal measurements is needed. We present below the normal values of pelvic measurement related indicators. External measurements: The indicators reflecting the transverse diameter of the pelvic inlet are the inter-iliac spine diameter (normal value is 23-26 cm) and the inter-iliac crest diameter (normal value is 25-28 cm). The indicators reflecting the anterior-posterior diameter of the pelvic entrance are the sacro-pubic outer diameter (normal value is 18-20 cm), and the indicators reflecting the exit plane are the sciatic tuberosity interdiameter (normal value is 8.5-9.5 cm) and the posterior sagittal diameter of the exit (normal value is 8-9 cm). When the sum of the posterior sagittal diameter of the exit and the sciatic tuberosity interdiameter value is >15 cm, it indicates that the pelvic exit stenosis is not obvious. In addition, there is the pubic arch angle (normal value is 90°, less than 80° is abnormal). Internal measurements: the diagonal diameter (normal value is 12.5-13 cm, this value minus 1.5-2 cm is the length of the anterior-posterior diameter of the pelvic inlet, also known as the true union diameter), which reflects the anterior-posterior diameter of the pelvic inlet; the indicators of the middle pelvis are the sciatic interspinous diameter (normal value is about 10 cm) and the width of the sciatic notch (normal value is about 5.5-6 cm). If you are in good health, your pelvis is normal, your baby is a good size, and there is no significant cephalopelvic disproportion, your doctor will recommend a vaginal delivery. However, the force of labor (also known as contractions) cannot be predicted well before delivery, and the true turn of the fetus along the birth canal under the action of contractions can only be known after delivery by regular observation of the labor process. Therefore, it is possible to change the delivery method temporarily during labor for the safety of mother and fetus due to abnormal labor or fetal intolerance (e.g. fetal distress), but this is not the common perception of suffering from a “second chance”. During labor, if contractions are weak, the doctor may break the membranes manually to bring the fetal head closer and compress the cervix to promote contractions, or use intravenous low-concentration indocin to strengthen contractions, or use sedatives or contraction inhibitors to slow contractions if they are uncoordinated or too strong. In addition, the mother’s vital signs as well as the baby’s fetal heart rate and amniotic fluid properties are monitored regularly. The concept of induction of labor is to induce labor before delivery, when the mother and fetus are unfit to continue the pregnancy due to some conditions, and when vaginal delivery is available, medications (such as low-concentration contraction drips, prostaglandin preparations, etc.) or good cervical scoring can be used, or manual rupture of membranes can be performed to induce contractions into spontaneous labor. Most of the inductions are successful.