Placenta Previa Case File

Placenta Previa Case File

Eugene C. Toy, MD, Patti Jayne Ross, MD, Benton Baker III, MD, John C. Jennings, MD

CASE 10

A 30-year-old G5P4 woman at 32 weeks’ gestation complains of significant bright red vaginal bleeding. She denies uterine contractions, leakage of fluid, or trauma. The patient states that 4 weeks previously, after she had engaged in sexual intercourse, she experienced some vaginal spotting. On examination, her blood pressure is 110/60 mm Hg, heart rate (HR) is 80 beats per minute (bpm), and temperature is 99°F (37.2°C). The heart and lung examinations are normal. The abdomen is soft and uterus nontender. Fetal heart tones are in the range of 140 to 150 bpm.

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ANSWER TO CASE 10:

Placenta Previa                                                           

Summary: A 30-year-old G5P4 woman at 32 weeks’ gestation complains of painless vaginal bleeding. Four weeks previously, she experienced some postcoital vaginal spotting. The abdomen is soft and uterus nontender. Fetal heart tones are in the range of 140 to 150 bpm.

• Next step: Ultrasound examination.
• Most likely diagnosis: Placenta previa.
• Long-term management: Expectant management as long as the bleeding is not excessive. Cesarean delivery at 34 weeks’ gestation (see new reference later in this case).

ANALYSIS

Objectives

1. Know the differential diagnosis of antepartum bleeding.
2. Understand that painless vaginal bleeding is consistent with placenta previa.
3. Understand that the ultrasound examination is a good method for assessing placental location.

Considerations

This patient is experiencing antepartum vaginal bleeding (bleeding after 20 weeks’ gestation). Because of the painless nature of the bleeding and lack of risk factors for placental abruption, this case is more likely to be placenta previa, defined as the placenta overlying the internal os of the cervix. Placental abruption (premature separation of the placenta) usually is associated with painful uterine contractions or excess uterine tone. The history of postcoital spotting earlier during the pregnancy is consistent with previa because vaginal intercourse may induce bleeding. The ultrasound examination is performed before a vaginal examination because vaginal manipulation (even a speculum examination) may induce bleeding. Because the patient is hemodynamically stable, and the fetal heart tones are normal, expectant management is the best therapy at 32 weeks’ gestation (due to the prematurity risks). If the same patient were at 35 to 36 weeks’ gestation, delivery by cesarean section would be prudent.

APPROACH TO:

Antepartum Vaginal Bleeding                                                   

DEFINITIONS

ANTEPARTUM VAGINAL BLEEDING: Vaginal bleeding occurring after 20 weeks gestation.

PLACENTA PREVIA: The placenta completely covers the internal os of the uterine cervix (Figure 10– 1).

MARGINAL PLACENTA PREVIA: The placenta lies within 2 cm of the internal os of the cervix, but does not fully cover it.

LOW-LYING PLACENTA: The edge of the placenta is within 2 cm of the internal cervical os.

PLACENTAL ABRUPTION: Premature separation of a normally implanted placenta.

VASA PREVIA: Umbilical cord vessels that insert into the membranes with the vessels overlying the internal cervical os, thus being vulnerable to fetal exsanguination upon rupture of membranes.

Figure 10–1. Types of placenta previa. Complete placenta previa (A), marginal placenta previa (B), and low-lying placentation (C) are depicted.

CLINICAL APPROACH

Antepartum hemorrhage is defined as significant vaginal bleeding after 20 weeks’ gestation. The two most common causes of significant antepartum bleeding are placental abruption and placenta previa (Table 10– 1). The main differentiator based on a patient’s history is that the vaginal bleeding is painless in a previa and painful in an abruption secondary to contractions. Placenta previa affects approximately 0.4% of deliveries, of which 70% to 80% will have at least one episode of bleeding. When the patient complains of antepartum hemorrhage, the physician should first rule out placenta previa by ultrasound even before a speculum or digital examination, since these maneuvers may induce bleeding. Ultrasound is an accurate method of assessing placental location. At times, transabdominal sonography may not be able to visualize the placenta, and transvaginal ultrasound is necessary and is more reliable for visualizing the internal cervical os.

The natural history of placenta previa is such that the first episode of bleeding does not usually cause sufficient concern as to necessitate delivery. Hence, a woman with a preterm gestation and placenta previa is usually observed on bed rest and complete pelvic rest in an effort to prolong gestation and avoid morbidity of fetal prematurity. Often, the second or third episode of bleeding forces delivery. The bleeding from previa rarely leads to coagulopathy, as opposed to that of placental abruption. Because the lower uterine segment is poorly contractile, postpartum bleeding may ensue. Several risk factors have been cited including parity, increased maternal age, smoking, multiple gestations, prior curettage, and prior cesarean delivery. Of note, placenta accreta (invasion of the placenta into the uterus) is more common with placenta previa, particularly in the presence of a uterine scar such as after a cesarean delivery. Timing of delivery depends on clinical circumstances for placenta previa and placenta accreta. A persistent hemorrhage mandates cesarean delivery regardless of gestational age. In asymptomatic patients, cesarean section as early as 34 weeks’ gestation appears to balance the fetal risk of prematurity and the

Table 10–1 • RISK FACTORS FOR PLACENTA PREVIA

Grand multiparity Prior cesarean delivery Prior uterine curettage Previous placenta previa Multiple gestation

maternal benefit of a scheduled delivery. The National Institutes of Health concluded that elective delivery is ideal at 36-37 completed weeks for these patients, but practices still vary. There is no demonstrated benefit to performing amniocentesis for fetal lung maturity prior to delivery at any gestational age.

COMPREHENSION QUESTIONS

10.1 A 28-year-old woman at 32 weeks’ gestation is seen in the obstetrical (OB) triage area for vaginal bleeding described as significant with clots. She denies cramping or pain. An ultrasound is performed revealing that the placenta is covering the internal os of the cervix. Which of the following is a risk factor for this patient’s condition?

A. Prior salpingitis

B. Hypertension

C. Multiple gestations

D. Polyhydramnios

10.2 A 21-year-old patient at 28 weeks’ gestation has vaginal bleeding and is diagnosed with placenta previa. Which of the following is a typical feature of this condition?

A. Painful bleeding

B. Commonly associated with coagulopathy

C. First episode of bleeding is usually profuse

D. Associated with postcoital spotting

10.3 A 33-year-old woman at 37 weeks’ gestation, confirmed by first-trimester sonography, presents with moderately severe vaginal bleeding. She is noted on sonography to have a placenta previa. Which of the following is the best management for this patient?

A. Induction of labor

B. Tocolysis of labor

C. Cesarean delivery

D. Expectant management

E. Intrauterine transfusion

10.4 A 22-year-old G1P0 woman at 34 weeks’ gestation presents with moderate vaginal bleeding and no uterine contractions. Her blood pressure (BP) is 110/ 60 mm Hg and heart rate (HR) 103 beats per minute (bpm). The abdomen is nontender. Which of the following sequence of examinations is most appropriate?

A. Speculum examination, ultrasound examination, digital examination

B. Ultrasound examination, digital examination, speculum examination

C. Digital examination, ultrasound examination, speculum examination

D. Ultrasound examination, speculum examination, digital examination

10.5 An 18-year-old adolescent female is noted to have a marginal placenta previa on an ultrasound examination at 22 weeks’ gestation. She does not have vaginal bleeding or spotting. Which of the following is the most appropriate management?

A. Schedule cesarean delivery at 39 weeks

B. Schedule an amniocentesis at 34 weeks and deliver by cesarean if the fetal lungs are mature

C. Schedule an MRI examination at 35 weeks to assess for possible percreta involving the bladder

D. Reassess placental position at 32 weeks’ gestation by ultrasound

E. Recommend termination of pregnancy

ANSWERS

10.1 C. Multiple gestation, with the increased surface area of placentation, is a risk factor for placenta previa. Hypertension is not a risk factor for placenta previa; however, it is one of the main risk factors for placental abruption. Polyhydramnios, due to the excess amount of amniotic fluid in the amniotic sac, is also a risk factor for placenta abruption. Salpingitis involves inflammation and infection of the fallopian tubes and over time may lead to permanent scarring of the tubes. Since this particular process is limited to the tubes, there is not an increased risk of placenta previa; rather there is an increased risk of ectopic pregnancy.

10.2 D. Postcoital spotting is a common complaint in a patient with placenta previa. Unlike placenta abruption, placenta previa is not commonly associated with coagulopathy, painful bleeding, or having a profuse first episode of bleeding. The main distinguishing factor between a previa and abruption is the presence or absence of pain. With abruption, painful uterine contractions are typically the chief complaint, whereas previa is painless. Although the first episode of bleeding with a previa usually does not raise enough concern to deliver immediately, the second or third bleeding episodes will send the patient to the operation room (OR) for a cesarean delivery.

10.3 C. The best plan for placenta previa at term is cesarean delivery. There is no need to place the patient at risk for hemorrhage when the fetus’ lungs are mature enough for life outside the womb; therefore, expectant management would not be the best choice for this scenario. A patient with a scheduled cesarean delivery does not need to be induced for labor, nor does she need tocolysis since the status of the patient’s labor is typically insignificant in a cesarean delivery. A patient with previa should not deliver vaginally since the lower uterine segment is poorly contractile, and postpartum bleeding may ensue. An intrauterine transfusion is also not indicated for this patient because the baby is going to be delivered and will be independent of the mother’s blood supply. Even in the setting of an Rh– mother with an Rh+ fetus, an intrauterine transfusion before delivery would pose a significantly greater risk to the mother and baby than waiting to evaluate the situation after birth.

10.4 D. Ultrasound should be performed first to rule out previa, speculum examination second to assess the cervix and look for lacerations, and finally digital examination. Performing either a speculum examination or digital examination before evaluating the patient with ultrasound puts the patient at risk for hemorrhage. In the setting of a previa, the lower uterine segment and cervix are highly vascularized, and varices of the cervix may be visualized on speculum examination in some situations; however, the speculum itself may cause trauma to these varices and induce bleeding. A blind digital examination may result in further separation of the placenta from the uterus, which could also cause significant bleeding.

10.5 D. Very often, a marginal or low-lying placenta previa at the early second trimester will resolve by transmigration of the placenta. It is too early to discuss scheduling a cesarean delivery since the placenta previa may resolve and allow for vaginal delivery. An ultrasound should be repeated in the third trimester to see whether or not the placenta has migrated. There would be no reason to be concerned about a percreta if the placenta migrates to a more favorable position; therefore, scheduling a magnetic resonance imaging (MRI) is not indicated at this time. In addition, an MRI is expensive, but it may be useful in the case of ultrasound-negative antepartum vaginal bleeding. If there is suspicion that a percreta exists, a previa has most likely already been diagnosed in the late second trimester or third trimester, so a scheduled cesarean delivery would most likely already be in the plan. During the cesarean, the physician will be able to assess the extent of the placental implantation and base management on how far the placenta has penetrated through the uterine wall. Placenta percreta and increta are usually diagnosed during a cesarean delivery and not radiographically. Amniocentesis for fetal lung maturity is not necessary in the setting of placenta previa at any gestational age. Recommending termination of pregnancy would be inappropriate in this case. Even if the patient has a placenta previa at the time of delivery, both the mother and baby have an excellent prognosis if a cesarean delivery is performed.

    CLINICAL PEARLS    

» Painless antepartum vaginal bleeding suggests the diagnosis of placenta previa. » Ultrasound is the diagnostic test of choice in assessing placenta previa and should be performed before digital or speculum examination. » Cesarean section is the best route of delivery for placenta previa. » Placenta previa, in the face of prior cesarean deliveries, increases the risk of placenta accreta. » When placenta previa is diagnosed at an early gestation, such as second trimester, repeat sonography is warranted since many times the placenta will move away from the cervix (transmigration).

REFERENCES

American College of Obstetricians and Gynecologists. Postpartum hemorrhage. ACOG Practice Bulletin 76. Washington, DC; 2006. (Reaffirmed 2015.) 

Balayla J, Wo BL, Bedard MJ. A late-preterm, early-term stratified analysis of neonatal outcomes by gestational age in placenta previa: defining the optimal timing for delivery. J Matern Fetal Neonatal Med. 2015 January;8:1-6. 

Cunningham FG, Leveno KJ, Bloom SL, et al. Obstetrical hemorrhage. In: Williams Obstetrics. 24th ed. New York, NY: McGraw-Hill; 2014:780-828. 

Gabbe SG, Niebyl JR, Simpson JL, et al. Antepartum and postpartum hemorrhage. In: Obstetrics Normal and Problem Pregnancies. 6th ed. Philadelphia, PA: Elsevier; 2012:415-444. 

Kim M, Hyashi RH, Gambone JC. Obstetrical hemorrhage and puerperal sepsis. In: H acker NF, Gambone JC, Hobel CJ, eds. Essentials of Obstetrics and Gynecology. 5th ed. Philadelphia, PA: Saunders; 2009:128-138. 

Masselli G, Brunelli R, Parasassi T, Perrone G, Gualdi G. Magnetic resonance imaging of clinically stable late pregnancy bleeding: beyond ultrasound. Eur Radiol. 2011;21:1841-1849. 

Robinson BK, Grobman WA. Effectiveness of timing strategies for delivery of individuals with placenta previa and accreta. Obstet Gynecol. 2010 October;116(4):835-842. 

Spong CY, Mercer BM, D’Alton M, Kilpatrick S, Blackwell S, Saade G. Timing of indicated late-preterm and early-term birth. Obstet Gynecol. 2011 August;118(2 Pt 1):323-333.

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