Although natural childbirth offers numerous benefits, some pregnant women are unsuitable for vaginal delivery, and the likelihood of a successful vaginal birth is not high. I. "Obstetric Factors" These are situations where vaginal delivery is inadvisable solely due to the physiological conditions of the fetus and mother. Such cases include: 1. Macrosomia A fetus weighing 4000g or more, or with a biparietal diameter exceeding 9.5cm, is classified as macrosomic.A large fetus increases the likelihood of surgical delivery, which may cause brachial plexus injury, clavicle fracture, intracranial hemorrhage, shoulder dystocia, neonatal asphyxia, or even death.For the mother, severe lacerations of the soft birth canal, uterine rupture, coccyx fractures, urinary incontinence, fecal incontinence, and other complications increase the likelihood of surgical delivery and heighten infection risks. Weak uterine contractions and prolonged labor may lead to postpartum hemorrhage. Damage to pelvic floor tissues can result in uterine prolapse later on.
2. Fetal Malpresentation
Generally refers to an abnormal fetal position within the uterus after 30 weeks of gestation, more common in mothers with lax abdominal walls and multiparous women. Malpresentations include breech, transverse, occipito-posterior, and face presentations. Breech presentation is most frequent, while transverse presentation poses the greatest risk to both mother and baby.Abnormal fetal position can cause secondary uterine contraction weakness, prolonging labor and often necessitating surgical delivery. This increases the risk of soft birth canal injuries, postpartum hemorrhage, and infection. Prolonged compression of the soft birth canal by the fetal head may result in ischemic necrosis and detachment, forming genital tract fistulas. If obstructed labor occurs and is not promptly managed, uterine rupture may ensue, threatening the mother's life.Prolonged second stage of labor and increased need for operative delivery may cause prolonged compression of the fetal head, potentially leading to intracranial hemorrhage, neonatal distress, and asphyxia. Facial compression can deform the infant's face, causing cyanosis and swelling of the skin, particularly noticeable around the lips. This impairs sucking ability and, in severe cases, may cause laryngeal edema affecting swallowing and breathing.
3. Maternal Pelvic Narrowing or Tilting
Pelvic narrowing or tilting refers to abnormally short pelvic dimensions or structural abnormalities, resulting in a pelvic cavity smaller than the space required for the presenting part to pass through. This obstructs descent of the presenting part, hindering smooth labor progression.Narrowing at the pelvic inlet plane often leads to malpresentation, frequently causing secondary uterine inertia that prolongs or halts labor. Narrowing at the mid-pelvic plane impedes fetal head internal rotation, causing prolonged head entrapment within the birth canal. This compression of soft tissues results in local ischemia, edema, necrosis, and tissue sloughing, potentially forming postpartum genital tract fistulas. Premature rupture of membranes and operative delivery increase infection risks.Severe obstructed labor, if not promptly managed, can lead to threatened uterine rupture or even uterine rupture, threatening the mother's life. For the baby, it causes fetal distress or even death; prolonged labor, pressure on the fetal head, and ischemia/hypoxia increase the risk of intracranial hemorrhage; narrow birth canal and increased likelihood of operative delivery heighten the risk of neonatal birth injuries and infections.
These conditions can be identified through examinations prior to natural delivery. Physicians will then advise the mother that vaginal delivery is inadvisable, necessitating a cesarean section.
II. Medical Conditions
Certain uncommon medical conditions in pregnant women may contraindicate natural delivery. These include:
4. Pregnancy Complicated by Heart Disease
This represents a severe obstetric complication and remains a primary cause of maternal mortality, with an incidence rate of 0.5–1.5%.Pregnancy enlarges the uterus and increases blood volume, placing additional strain on the heart. During labor, uterine and skeletal muscle contractions drive large volumes of blood toward the heart. Postpartum increases in circulating blood volume can easily trigger heart failure in compromised cardiac function. Simultaneously, prolonged chronic hypoxia may cause intrauterine growth restriction and fetal distress.Whether a heart disease patient can safely navigate pregnancy and delivery depends on cardiac function, necessitating high vigilance for this condition.
Pregnant women with such conditions should select an appropriate delivery method in advance. For those with Class I–II heart failure, a small fetus, normal fetal position, and favorable cervical conditions, vaginal delivery under close monitoring may be considered.Elective cesarean section is recommended for cases with a small fetus, unfavorable birth canal conditions, or heart function stages III–IV.On the basis of liver failure, postpartum hemorrhage caused by coagulation disorders, gastrointestinal bleeding, and infections serve as triggers, ultimately leading to hepatic encephalopathy and hepatorenal syndrome. This is one of the primary causes of maternal mortality. Viral hepatitis during pregnancy can infect the fetus through vertical transmission, with particularly high rates of mother-to-child transmission for hepatitis B. Viral hepatitis is closely associated with the onset of Down syndrome.Viral hepatitis during early pregnancy approximately doubles the incidence of fetal malformations. Rates of miscarriage, preterm birth, stillbirth, and neonatal mortality are significantly elevated.
6. Idiopathic Thrombocytopenic Purpura
This condition represents a common obstetric complication involving hematological disorders. Pre-pregnancy manifestations typically include menorrhagia and gingival bleeding.
For fetuses diagnosed with thrombocytopenia during late pregnancy, vaginal delivery is contraindicated to reduce the risk of neonatal intracranial hemorrhage; cesarean section is recommended.
7. Hyperthyroidism
In cases of worsening hyperthyroidism during late pregnancy, cesarean section should be the primary delivery method after active treatment of the underlying condition to prevent thyroid crisis.
8. Severe Genital Infections
Conditions such as genital warts may cause birth canal obstruction and pose a risk of neonatal infection during delivery, making cesarean section the preferred option.
9. Gestational Diabetes Mellitus
Approximately 5% of pregnant women develop gestational diabetes, with the primary risk being macrosomia (large baby). This increases the likelihood of requiring forceps or vacuum extraction during vaginal delivery.