Placenta Previa

Obstetrics

Clinicals - History

Fact Explanation
Introduction Placenta Previa is an obstetric complication where the placenta is inserted to the lower uterine segment partially or as a whole which can result in antepartum hemorrhage. Introduction
Placenta Previa is an obstetric complication where the placenta is inserted to the lower uterine segment partially or as a whole which can result in antepartum hemorrhage.
Painless per vaginal bleeding in the second/third trimester. This is the common presentation of the placenta previa. So a clinical suspicion should be raised when a women after 20 weeks of gestation presents with painless vaginal bleeding Painless per vaginal bleeding in the second/third trimester.
This is the common presentation of the placenta previa. So a clinical suspicion should be raised when a women after 20 weeks of gestation presents with painless vaginal bleeding
Bleeding can at times be associated with a trigger factor. eg : Coitus, exercise Bleeding can be precipitated by shearing forces which cause provoked bleeding in this cases Bleeding can at times be associated with a trigger factor. eg : Coitus, exercise
Bleeding can be precipitated by shearing forces which cause provoked bleeding in this cases
Asymptomatic Women can remain asymptomatic regardless of the degree of placenta previa during early stages of pregnancy hence the need for screening antenatally Asymptomatic
Women can remain asymptomatic regardless of the degree of placenta previa during early stages of pregnancy hence the need for screening antenatally
Factors which pose increased risk in Placenta Previa Although the exact pathophysiology is unknown, uterine scarring has been believed to result in abnormal placentation.
Other Risk factors include adverse maternal age, higher parity, past history of placenta previa, previous cesarean section, previous curettage and an abnormal uterus.
Factors which pose increased risk in Placenta Previa
Although the exact pathophysiology is unknown, uterine scarring has been believed to result in abnormal placentation.
Other Risk factors include adverse maternal age, higher parity, past history of placenta previa, previous cesarean section, previous curettage and an abnormal uterus.
History of Endometriosis and subfertility Endometriosis thought to be responsible for progesterone resistant endometrium during the placentation History of Endometriosis and subfertility
Endometriosis thought to be responsible for progesterone resistant endometrium during the placentation
History of Assisted Conception Although not fully proven, It is thought that mechanical placement of embryos cause release of prostaglandins which cause uterine contractions which result in placentation in lower segment. History of Assisted Conception
Although not fully proven, It is thought that mechanical placement of embryos cause release of prostaglandins which cause uterine contractions which result in placentation in lower segment.

Clinicals - Examination

Fact Explanation
Tachycardia, hypotension and reduced urine output. Massive blood loss can lead to a shock state. Massive blood loss is common with morbid adherence of the placenta. Tachycardia, hypotension and reduced urine output.
Massive blood loss can lead to a shock state. Massive blood loss is common with morbid adherence of the placenta.
A high unengaged head The fetal head fails to engage since the placenta occupies the lower pole of the uterus. A high unengaged head
The fetal head fails to engage since the placenta occupies the lower pole of the uterus.
Abnormal lie/malpresentation Abnormal placentation hinders spontaneous version. Abnormal lie/malpresentation
Abnormal placentation hinders spontaneous version.
Speculum examination Carefully performed, it can be useful to identify a lower tract lesion responsible for ante-partum hemorrhage. Cervical dilatation can also be assessed. Remember that digital examination of the vagina should be avoided is placenta previa is suspected. Speculum examination
Carefully performed, it can be useful to identify a lower tract lesion responsible for ante-partum hemorrhage. Cervical dilatation can also be assessed. Remember that digital examination of the vagina should be avoided is placenta previa is suspected.

Investigations - Diagnosis

Fact Explanation
Ultrasound scan Can confirm placental site.

Both trans abdominal and trans vaginal ultrasound scans are used.
Trans-vaginal ultrasound scan is 87.5% sensitive and 98.8% specific in the diagnosis of placenta praevia in the second and third trimester.
Trans-abdominal ultrasound scan is 79%-82% sensitive and 38%-97% specific in the diagnosis of placenta praevia.

Trans vaginal USS is more accurate in diagnosing placenta previa. It is superior at detecting posteriorly situated placenta previa and is more accurate in obese patients when compared to trans abdominal USS.
Trans vaginal scans are safe with minimum risk of hemorrhagic complications.

Additional information that can be gained include fetal size, fetal presentation and amniotic fluid index.
Ultrasound scan
Can confirm placental site.

Both trans abdominal and trans vaginal ultrasound scans are used.
Trans-vaginal ultrasound scan is 87.5% sensitive and 98.8% specific in the diagnosis of placenta praevia in the second and third trimester.
Trans-abdominal ultrasound scan is 79%-82% sensitive and 38%-97% specific in the diagnosis of placenta praevia.

Trans vaginal USS is more accurate in diagnosing placenta previa. It is superior at detecting posteriorly situated placenta previa and is more accurate in obese patients when compared to trans abdominal USS.
Trans vaginal scans are safe with minimum risk of hemorrhagic complications.

Additional information that can be gained include fetal size, fetal presentation and amniotic fluid index.
Cardiotocography Assessment of fetal well-being.
Parameters to assess are base line heart rate, Variability & presence of decelerations. Fetal bradycardia, reduced variability and late decelerations are features of fetal distress.
Cardiotocography
Assessment of fetal well-being.
Parameters to assess are base line heart rate, Variability & presence of decelerations. Fetal bradycardia, reduced variability and late decelerations are features of fetal distress.
Magnetic resonance imaging (MRI) Can be used if morbidly adherent placenta is suspected.
placenta previa situated over previous uterine scars or sites of endometrial damage can lead to abnormal placental invasion.
Magnetic resonance imaging (MRI)
Can be used if morbidly adherent placenta is suspected.
placenta previa situated over previous uterine scars or sites of endometrial damage can lead to abnormal placental invasion.
Kleihauer test Performed in rhesus D negative women to quantify feto-maternal
hemorrhage in order to calculate the dose of anti-D immunoglobulin required.
Kleihauer test
Performed in rhesus D negative women to quantify feto-maternal
hemorrhage in order to calculate the dose of anti-D immunoglobulin required.

Investigations - Management

Fact Explanation
Full blood count To assess the hemoglobin level of the patient. Full blood count
To assess the hemoglobin level of the patient.
Blood group & cross matching. Blood products should be available in the setting of massive hemorrhage to manage shock. In major bleeds 4 units of blood are cross-matched. Blood group & cross matching.
Blood products should be available in the setting of massive hemorrhage to manage shock. In major bleeds 4 units of blood are cross-matched.
Serum electrolytes/ Serum creatinine. To screen for metabolic derangements. Assessment of renal function since massive hemorrhage will lead to pre- renal failure. Serum electrolytes/ Serum creatinine.
To screen for metabolic derangements. Assessment of renal function since massive hemorrhage will lead to pre- renal failure.
Coagulation screen Complications such as disseminated intravascular coagulation (DIC) can occur. Coagulation screen
Complications such as disseminated intravascular coagulation (DIC) can occur.
Placental site localization by ultrasound scan Routine ultrasound scanning at 20 weeks of gestation should include placental site localization. Placental site localization by ultrasound scan
Routine ultrasound scanning at 20 weeks of gestation should include placental site localization.

Management - Supportive

Fact Explanation
Prevent and treat anemia Recurrent mild bleeds can lead to anemia. An anemic patient will cope less well if faced with massive hemorrhage. Maternal anemia may also reduce fetal growth. Prevent and treat anemia
Recurrent mild bleeds can lead to anemia. An anemic patient will cope less well if faced with massive hemorrhage. Maternal anemia may also reduce fetal growth.
Educating & counseling the mother and caregivers Placenta previa can lead to massive hemorrhage. Early presentation to healthcare facility can reduce maternal and neonatal mortality.
The patient should be counseled on the risk of preterm delivery, need for blood transfusions, need for specific interventions such as cesarean section.
Educating & counseling the mother and caregivers
Placenta previa can lead to massive hemorrhage. Early presentation to healthcare facility can reduce maternal and neonatal mortality.
The patient should be counseled on the risk of preterm delivery, need for blood transfusions, need for specific interventions such as cesarean section.
Observation Patient should be managed in ward with constant observation. If managed at home certain facilities should be available for quick trasnportation to the hospital and there should be caregiver available at all times. Observation
Patient should be managed in ward with constant observation. If managed at home certain facilities should be available for quick trasnportation to the hospital and there should be caregiver available at all times.
Prevention of venous thromboembolism (VTE) Pregnancy may predispose to thromboembolic events, prolonged immobilization during the hospital stay may further increase this risk. Maintain adequate hydration and encourage mobilization of the patient. Thromboembolic deterrent (TED) stockings can be used. Prophylactic anti-coagulation should be considered in high risk patients. Prevention of venous thromboembolism (VTE)
Pregnancy may predispose to thromboembolic events, prolonged immobilization during the hospital stay may further increase this risk. Maintain adequate hydration and encourage mobilization of the patient. Thromboembolic deterrent (TED) stockings can be used. Prophylactic anti-coagulation should be considered in high risk patients.

Management - Specific

Fact Explanation
Vaginal delivery Only possible if lower placental edge >2cm from the internal os.
Placental site & degree of placenta previa should also be considered. Minor placenta previa in an anterior position favors vaginal delivery.
Vaginal delivery
Only possible if lower placental edge >2cm from the internal os.
Placental site & degree of placenta previa should also be considered. Minor placenta previa in an anterior position favors vaginal delivery.
Caesarean section In an asymptomatic patient aim for delivery at 38 weeks. The time of elective delivery should planned according to each patient. A balance should be struck between prolonging pregnancy till fetal maturity is reached while not risking maternal or fetal life.

Most often a low transverse uterine incision is used. Avoid cutting through the placenta by gaining access to the upper edge and operating above this.
Caesarean section
In an asymptomatic patient aim for delivery at 38 weeks. The time of elective delivery should planned according to each patient. A balance should be struck between prolonging pregnancy till fetal maturity is reached while not risking maternal or fetal life.

Most often a low transverse uterine incision is used. Avoid cutting through the placenta by gaining access to the upper edge and operating above this.
Optimum management of delivery. Delivery should be supervised by an experienced obstetrician together with an experienced anesthesiologist. Blood and blood products should be cross matched and made available prior to the delivery. Prior planning on management should be discussed at a multi disciplinary meeting. Discussion with the patient should include possible interventions such as hysterectomy, leaving the placenta in place, and interventional radiological procedures. Availability of a critical care services and neonatal care should be arranged beforehand. Optimum management of delivery.
Delivery should be supervised by an experienced obstetrician together with an experienced anesthesiologist. Blood and blood products should be cross matched and made available prior to the delivery. Prior planning on management should be discussed at a multi disciplinary meeting. Discussion with the patient should include possible interventions such as hysterectomy, leaving the placenta in place, and interventional radiological procedures. Availability of a critical care services and neonatal care should be arranged beforehand.
Following delivery anticipate and promptly manage postpartum hemorrhage. Anticipate increased post partum bleeding as contraction and retraction of the lower segment is less than the upper segment of the uterus. Following delivery anticipate and promptly manage postpartum hemorrhage.
Anticipate increased post partum bleeding as contraction and retraction of the lower segment is less than the upper segment of the uterus.
Management of mild self limiting bleeds during the intra partum period. Admit the patient for monitoring of the progression of bleeding and vital parameters. Monitor fetal well-being by performing a cardio-tocograph. If a preterm delivery is expected antenatal corticosteroids to promote fetal lung maturation should be started. Recommended regimens are: beta-methasone 12 mg given intramuscularly in two doses or dexamethasone 6 mg given intramuscularly in four doses are the steroid regimes of choice. Administer anti D if the mother is rhesus negative - Antepartum hemorrhage can lead to sensitization. Management of mild self limiting bleeds during the intra partum period.
Admit the patient for monitoring of the progression of bleeding and vital parameters. Monitor fetal well-being by performing a cardio-tocograph. If a preterm delivery is expected antenatal corticosteroids to promote fetal lung maturation should be started. Recommended regimens are: beta-methasone 12 mg given intramuscularly in two doses or dexamethasone 6 mg given intramuscularly in four doses are the steroid regimes of choice. Administer anti D if the mother is rhesus negative - Antepartum hemorrhage can lead to sensitization.
Anticipate invasive placentation. Placenta previa with previous caesarean section can lead to a morbidly adherent placenta. Massive hemorrhage can occur even requiring a cesarean hysterectomy. Anticipate invasive placentation.
Placenta previa with previous caesarean section can lead to a morbidly adherent placenta. Massive hemorrhage can occur even requiring a cesarean hysterectomy.
Management of a severe bleed with or without fetal/maternal compromise Resuscitation of the mother should be according to the structured ABC approach. Secure airway, administer oxygen, establish intravascular access with two wide bore canulae. Start fluid resuscitation with crystalloids, blood should be transfused if necessary. Continuous monitoring fetal well-being should be performed. Immediate delivery is indicated and cesarean section is recommended. Management of a severe bleed with or without fetal/maternal compromise
Resuscitation of the mother should be according to the structured ABC approach. Secure airway, administer oxygen, establish intravascular access with two wide bore canulae. Start fluid resuscitation with crystalloids, blood should be transfused if necessary. Continuous monitoring fetal well-being should be performed. Immediate delivery is indicated and cesarean section is recommended.
Cervical cerclage Cervical cerclage is not currently recommended in practice. Cervical cerclage
Cervical cerclage is not currently recommended in practice.
Tocolytic agents Tocolytics can be used selectively particularly in extreme prematurity. But Beta-mimetics can cause changes in the maternal cardiovascular system that could interfere with the response to hemorrhage. Tocolytic agents
Tocolytics can be used selectively particularly in extreme prematurity. But Beta-mimetics can cause changes in the maternal cardiovascular system that could interfere with the response to hemorrhage.

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