Antepartum vaginal bleeding: Vaginal bleeding occurring after 20 weeks' gestation.
Complete placenta previa: Placenta completely covers the internal os of the uterine cervix (Figure 14-1). Partial placenta previa: Placenta partially covers the internal cervical os. Marginal placenta previa: Placenta abuts against the internal os of the cervix (see Figure 14-1).
A. Complete placenta previa
B. Marginal placenta previa mm C. Low-lying placenta
Figure 14—1. Types of placenta previa. Complete placenta previa (A), marginal placenta previa (B), and low-lying placentation (C) are depicted.
Low-lying placenta: Edge of the placenta is within 2 to 3 cm of the internal cervical os (see Figure 14-1).
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 and thus are vulnerable to fetal exsanguination upon rupture of membranes.
Antepartum hemorrhage is defined as significant vaginal bleeding after 20 weeks' gestation. The two most common causes of significant antepartum bleeding are placenta abruption and placenta previa (Table 14-1). The classic presentation of previa bleeding is painless vaginal bleeding after the mid-second trimester, whereas placental abruption frequently presents with painful contractions. When the patient complains of antepartum hemorrhage, the physician should first rule out placenta previa by ultrasound even before a speculum or digital examination because these maneuvers may induce bleeding. Ultrasound is an accurate method for assessing placental location. At times, transabdominal sonography may not be able to visualize the placenta, and transvaginal ultrasound is necessary.
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 usually is observed on bed rest with the hope that time will be gained for fetal maturation. Often, the second or third episode of bleeding forces delivery. The bleeding from previa rarely leads to coagulopathy, as opposed to that from placenta abruption. At or near term (36-37 weeks), many practitioners will perform an amniocentesis to establish fetal lung maturity: if the fetal lungs appear mature, then delivery will be scheduled. As a general rule, the route of delivery is by cesarean section. Because the lower uterine segment is poorly contractile, postpartum bleeding may ensue. Also, 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 a prior cesarean incision.
RISK FACTORS FOR PLACENTA PREVIA
Grand multiparity Prior cesarean delivery Prior uterine curettage Previous placenta previa Multiple gestation
[ 14.11 Which ol" the following is a risk factor of placenta previa?
A. Prior salpingitis
C. Multiple gestation
[ 14.2] Which of the following is a typical feature of placenta previa?
A. Painful bleeding
B. Commonly associated with coagulopathy
C. First episode of bleeding usually is profuse
[14.3] 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
[ 14.4] A 22-year-old G1 PO woman at 34 weeks' gestation presents with moderate vaginal bleeding and no uterine contractions. Which of the following sequences 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
114.51 An 18-year-old woman is noted to have a marginal placenta previa on ultrasound examination at 22 weeks' gestation. Which of the following is the most appropriate management?
A. Schedule cesarean delivery at 39 weeks.
B. Schedule an amniocentesis at 36 weeks and deliver by cesarean section if the fetal lungs are mature.
C. Schedule a magnetic resonance imaging (MRI) examination at
35 weeks to assess for possible percreta involving the bladder.
D. Reassess placental position at 32 weeks
E. Recommend termination of pregnancy
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