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Placenta praevia (placenta previa AE) is an obstetric complication in which the placenta is attached to the uterine wall close to or covering the cervix.
ANTEPARTUM HAEMORRHAGE INTRODUCTION • Antepartum haemorrhage (APH) is defined as any vaginal bleeding occurring during pregnancy, starting from 20 weeks gestation until delivery of the fetus. • APH remains one of the leading causes of maternal mortality throughout the world. It may also have and adverse effect on the fetal and neonatal outcome. • In many cases the bleeding in APH is unavoidable, and if severe an urgent intervention will be life saving both to the mother and the fetus. CAUSES OF ANTEPARTUM HAEMORRHAGE OBSTETRIC CAUSES: • I. Maternal (placental site causes): – Bleeding is due to premature separation of the placenta. They are the most worrying causes as both the mother and her fetus are in danger, it includes: • Placenta praevia (bleeding from separation of an abnormally situated placenta). • Placental abruption (bleeding from separation of a normally situated placenta). • II. Fetal (rupture vasa praevia): – Vasa praevia (velamentous insertion of the cord with rupture of fetal vessels). • LOCAL GYNAECOLOGICAL CAUSES (extra-placental site): – Local causes are less worrying. They are due to local gynecological condition including: • Cervicitis and cervical erosion. • Benign cervical polyp or rarely malignant cervical carcinoma. • Severe vaginal infections or rarely vaginal trauma. PLACENTA PRAEVIA DEFINITION and INCIDENCE • Placenta praevia (PP) is a placenta that is encroaching on the lower uterine segment. It may be located over or very near the internal os. • Placenta praevia is relatively rare (1/300 to 1/500 pregnancies), however it may be the cause of one of the most serious and life threatening obstetric emergencies. • Placenta praevia may be associated with mild or severe bleeding which may be provoked or spontaneous. Such bleeding is from maternal and not fetal circulation, and is more likely to compromise the mother before it affects fetal condition CLASSIFICATION OF THE DEGREES OF PLACENTA PRAEVIA • Total placenta praevia (complete): The placenta completely covers the internal os. • Partial placenta praevia (incomplete): The placenta partially covers the internal os. • Marginal placenta praevia: The edge of the placenta is at the margin of the internal os. • Low lying placenta (PP lateralis): The placental encroaches on the lower uterine segment but its edge does not reach the internal os. (it is of little clinical significance). • N.B.: the nearer the placenta to the internal os, the more is the liability for earlier separation leading to more severe bleeding attacks, and liability to preterm termination of pregnancy. • N.B.: PP marginalis posterior is more dangerous than marginalis anterior because: • It encroaches on the true conjugate delaying engagement of the head. • Engagement of the head will compress the intact part of the placenta against the sacrum causing fetal asphyxia while leaving the lower separated part of placenta uncompressed leading to uncontrolled bleeding. AETIOLOGY AND RISK FACTORS • Advancing maternal age (>35 years). • Multiparity (para five or greater). • Prior caesarian delivery: the incidence increases with the number of previous C.S. • Multifetal pregnancy: the incidence reaches up to 40% in twin pregnancy. • Other causes of large placentae: as placenta membranacaea or multiple lobes (as bipartite). MECHANISM OF BLEEDING • During the 2nd half of pregnancy the lower uterine segment is progressively passively and painlessly stretching and elongating but the inelastic placenta cannot stretch in a similar pattern, so inevitable separation occurs (shearing effect) leading to unavoidable bleeding. PATHOLOGY OF PLACENTA PRAEVIA • The lower uterine segment: It is thin, vascular, and friable thus more liable to laceration. • The placenta: – Extends to the lower uterine segment, may reach or cover the internal os. – Higher incidence of placenta accreta, due to poor decidual reaction in the lower segment. • The umbilical cord: there is higher incidence of velamentous insertion and vasa praevia. CLINICAL DIAGNOSIS OF PLACENTA PRAEVIA • Clinical Symptoms of APH due to PP: • Vaginal bleeding in placenta praevia is characterized by being: – Causeless (unless it follows intercourse or vaginal examination). – Painless (unless it is associated with labour pains) – Recurrent (unless pregnancy is terminated with the first attack). – Bleeding is always revealed and bright red in colour. Clinical Signs in APH due to PP: • General signs related to bleeding: – The general condition is proportionate to amount of bleeding. – Anaemia is present if bleeding is severe or recurrent. – No signs of toxaemia of pregnancy as in some cases of placental abruption (see later). – Signs of hypovolaemic shock, if present, include: – Drowsiness, delirium or loss of consciousness. – Pallor, tachypnia, hypotension, and tachycardia (rapid and rising pulse). • N.B.: In APH due to PP, signs of hypovolaemic shock correlate with the severity of bleeding (amount of blood lost), the rate of blood loss (duration of bleeding), and the previous general condition of the patient (haemoglobin level and anaemia). Abdominal Examination in PP: • The abdomen and uterus are lax and not tender, so fetal parts and movements are easily felt. • Fundal level corresponds to the period of amenorrhea. • Malpresentations are common, and there is usually delayed engagement of the presenting part in the last weeks of pregnancy. • Fetal heart sounds (FHS) are usually audible and regular, except if severe bleeding compromises the fetal condition. Pelvic vaginal Examination: • Vaginal examination (PV) in PP is generally contra-indicated, as it may provoke an uncontrollable attack of bleeding due to placental separation. – Indications of PV examination: Only when active management is decided. – Aim of PV examination: To obtain the following data: • The degree of cervical effacement and dilatation, and the condition of the membranes. • The type and station of the presenting part and assessment of pelvic adequacy. • The degree of PP if present (placenta is felt as tough spongy mass by the index finger while a blood clot is friable). Precautions during vaginal examination if indicated: • It should NOT be done at home or even in hospital outpatient or emergency room. • It should be done ONLY in the operating theater under complete aseptic conditions. • Anaesthesia should be ready and blood transfusion is readily available • The settings for performing an immediate caesarean section are prepared Ultrasound diagnosis of PP: • Ultrasonography (US) is the gold standard in the diagnosis of placenta praeviae (PP). Placental localization can be easily made by US at the middle of the second trimester. By beginning of the third trimester partial and complete types of PP can be easily excluded during any attack of vaginal bleeding. • US, is also the gold standard in the differentiation between APH due to PP from that due to placental abruption. • Other additional US benefits include accurate estimation of fetal gestational age, amniotic fluid volume evaluation, assessment of fetal well being, and exclusion of major fetal anomalies. • Laboratory Investigations: – Complete blood picture (CBC), to detect anaemia necessitating blood transfusion. – Urine analysis: to exclude albuminuria associated with preeclampsia (PE). • DIFFERENTIAL DIAGNOSIS of APH due to PP: • Other causes of APH (placental abruption, vasa praevia, and local gynecologic causes). • Other causes of bleeding as severe hypertension and thrombocytopenic purpura, etc... MANAGEMENT OF APH due to PP: • Factors affecting the management of APH secondary to PP: – The severity of bleeding and its effect on the patient's general condition. – The duration of gestational age and its effect on fetal lung maturity. • The main lines of management in Placenta Praevia are: – Expectant (conservative) Management (continuation of pregnancy) – Active management (termination of pregnancy) Expectant Management • The aim of conservative (expectant) management is to allow pregnancy to continue until either fetal maturity is achieved, or labor pains start spontaneously. • Indications of expectant management: – Pregnancy < 37 weeks, with mild bleeding and absent labour pains. – Patient is in good general condition – Fetus is living and with no associated gross fetal anomalies. Lines of expectant management: • Complete bed rest, diet and vitamin support. • Correction of anaemia, if present, by oral or parentral iron therapy. • Localization of the placenta by US, to exclude placental abruption. • Laboratory investigations to check on the bleeding and coagulation profiles. • After complete cessation of bleeding, a local gynaecologic examination could be performed (speculum examination) to exclude local organic lesion. ACTIVE MANAGEMENT (TERMINATION OF PREGNANCY) • The aim of active management is the immediate termination of pregnancy whenever the fetus is mature or the bleeding is so severe compromising maternal and fetal health. • Indications of active management: – Any bleeding > 37 weeks gestation (even if mild or moderate). – Any severe bleeding irrespective of gestation age. – Patient with hypovolaemic shock or in poor general condition – Labour pains have already started. – Recurrent and persistent mild to moderate bleeding during expectant management. – Fetus is dead or with major fetal anomalies incompatible with life. Caesarean Section: • Indications specific to Placenta praevia: – Total (complete), or partial (incomplete), or marginal posterior types of PP. – Severe bleeding or patient in shock. – Moderate bleeding and cervix is closed. – Continuous bleeding during trial for vaginal delivery. – Fetal distress due to severe bleeding during pregnancy or during labour. • Other indications associated with PP: – Elderly primigravida, previous caesarean section, associated malpresentations, any degree of pelvic contraction, associated pregnancy complications as toxaemia or diabetes. Precautions during performing C.S. for Placenta praevia: • Anti-shock measurements including blood transfusion if needed. • The technique is by a lower segment C.S. • After performing the uterine incision the fetus is delivered before the placenta. • IV Oxytocin (syntocinon), ergometrin (methergin), prostaglandins, or mesoprostol (cytotec), can be used single or in combination to assure excellent uterine contractions capable of controlling expected postpartum haemorrhage. • In cases of uncontrollable bleeding with failure of above measures, we may do: – Bilateral ligation of the uterine arteries. – Unilateral or bilateral ligation of the anterior division of internal iliac artery. – Abdominal hysterectomy if above measures fail (or in grand multipara). Trial of vaginal delivery: • Indications: – Absence of any of the previously discussed indications for caesarean section. – PP lateralis or marginalis anterior, with minimal separation and bleeding. – Normal fetal well being (no fetal distress, no IUGR). – Fetus is in a cephalic presentation (best occipitoanterior position). – Favorable local pelvic examination (cervix is ripe, sufficiently dilated, pelvis adequate and head not in a high station) Method: Should be done in the following sequences. • Artificial rupture of membranes (ROM) : – Stops the shearing effect and separation of the placenta from lower segemnt – Allows more rapid descent of the head and compression of the bleeding sinuses. – Stimulates uterine contractions (prostaglandin release). • Intravenous oxytocin (unless contraindicated), in order to augment uterine contractions. • Care of the 3rd stage and puerperium to avoid postpartum haemorrhage and treat anaemia. Complications and effects of PP on pregnancy, labour and puerperium: • Unavoidable haemorrhage causing hypovolaemic shock if severe and anaemia if mild and recurrent. • Abortion, IUGR and IUFD (intrauterine fetal death). • Premature delivery (with all complications of prematurity). • Malpresentations and non-engagement of the presenting part (dysfunctional labour). • Predisposition to presentation and prolapse of cord. • Postpartum haemorrhage due to: – Defective retraction in the lower uterine segment so unable to close the bleeding sinuses. – Inertia of the upper uterine segment due to anaemia. – Retention of parts of the placenta due to abnormal adhesion to lower uterine segment. – Lower uterine segment is thin and vascular so liable to be torn during any manipulation. • Puerperal sepsis (due to anaemia and laceration).
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