Best Practice & Research Clinical Obstetrics & Gynaecology
6Caesarean section in cases of placenta praevia and accreta
Introduction
Placenta praevia and placenta accreta (abnormally invasive placenta) are two obstetric conditions that are closely linked with massive obstetric haemorrhage. Occasionally, they present with some degrees of intrauterine growth restriction. Placenta praevia is located in the lower uterine segment, which could result in inappropriate placental development owing to the particular development of their vessels.1 Placenta accreta is also known as abnormally morbid adherence of placenta or abnormally invasive placenta. This condition includes all degrees of placental invasion within this generic name of placenta accrete.2 Placenta percreta, however, which has the deepest degree of invasion, is usually described separately. Diagnosis for placenta praevia and placenta accreta is usually achieved by ultrasound; nevertheless, other investigations may be necessary when there is doubt or when the precise anatomy of placental invasion is required.3 Placenta accreta has a special type of supplementary circulation through newly formed vessels. The anatomical adhesion among vessels, and placental invasion into the myometrium and the surrounding tissues, pose a great surgical challenge. In these cases, the main objective of the caesarean section is to deliver the baby through a safe area and to avoid uncontrollable bleeding, as massive blood loss could turn into severe shock and coagulopathy in minutes.
Section snippets
General overview and definitions
Placenta praevia is a disorder that happens during pregnancy when the placenta is abnormally placed in the lower uterine segment, which at times covers the cervix. Placenta praevia can be classified according to its position in relation to the internal cervical external orifice into totally occlusive, partially occlusive or marginal. Normally, the placenta should develop relatively high up in the uterus, on the front or back uterine wall but, on some, occasions the placenta will be located in
Risk factors
Knowledge of risk factors is particularly important to distinguish among mild cases or in those that the image analysis is not in agreement with the individual's background. The incidence of placenta praevia is about one in every 250 births, and it is the cause of one-third of all cases of antepartum haemorrhage. Placenta praevia is associated with previous uterine scar, smoking, maternal age over 35 years, grandmultiparity, recurrent miscarriages, low socioeconomic status, infertility
Placenta praevia
Both placenta praevia and accreta are best diagnosed by ultrasound; this method is highly reliable, low cost, and provides clear signs for image interpretation. Ultrasound examination may diagnose placenta praevia and classify them in early stages. Although abdominal ultrasound can determine the placental position in relation to the cervical external orifice, transvaginal ultrasound is now well established as the preferred method for accurate localisation of a low-lying placenta. Because some
Placenta praevia
An initial assessment to determine the status of the mother and fetus is required. Although mothers used to be treated in the hospital from the first bleeding episode until birth, it is considered safe to treat placenta praevia on an outpatient basis if the fetus is at less than 30 weeks of gestation and the mother and the fetus are in good health. Clinical trials support the use of outpatient management for stable individuals.17, 18 The clinical outcomes of cases with placenta previa are
Scheduled surgery
When the placenta covers the lower uterine segment, it may be necessary to cross the placenta to deliver the baby,8 a manoeuvre that usually produces additional haemorrhage. Then, placental detachment could produce further bleeding, as a result of the poor contractility of the lower uterine segment and because of its increased blood supply. If the bleeding is not controlled promptly, the process may aggravate and end in coagulopathy or other severe complications.23 For this reason, a rational
Surgery for placenta accreta
No universal treatment exists for placenta accreta, because its management could be different according to personal or maternal preferences, experience, skills and resources.16 Although, several approaches are available, all of them will want to avoid maternal bleeding during delivery. At present, placenta accrete can be managed in three ways: (1) carry out a hysterectomy; (2) leave the placenta in situ; and (3) resect the invaded tissues with the entire placenta restoring uterine anatomy. Each
Hysterectomy
Hysterectomy, is the most common and historical treatment for placenta accrete. Nevertheless, it is not a simple procedure. Hysterectomy carried out by an unskilled surgeon could end quickly in severe complications or maternal death. The extreme difficulty of dissecting the tissues, presence of thick and friable vessels, and increased blood flow at term, make it almost impossible to carry out a safe hysterectomy without risk of haemodynamic and haemostatic deterioration.16 If resources or a
One-step conservative surgery
Although our primary objective in placenta accreta is to prevent bleeding, the ideal treatment of abnormal placentation should restore the uterine anatomy and ensure a new pregnancy with minimal risk of complications. According to this idea, a completely new approach for abnormal placentation to solve all problems of placenta accreta was originally designed.33 This procedure proposes, at first, the vascular interruption of newly formed vessels and vesical separation of the invaded tissues (like
Conclusion
Placenta praevia and accreta are usually located in the lower segment. Differential diagnosis between these conditions is routinely carried out, but mild or doubtful cases should be explored by multi-planar methods to avoid unexpected complications or unnecessary hysterectomies. Access to pelvic subperitoneal spaces and retrovesical dissection are key to achieving vascular control and haemostatic procedures. Accurate vascular control avoids bleeding and clinical consequences of haemorrhage,
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