Hematologic Disease in Pregnancy: The Obstetrician’s Perspective




Pregnancy can be a time of significantly increased morbidity and mortality in women with hematologic disease. With careful planning and preparation, most women can be cared for safely, resulting in a healthy mother and child. Management concerns in each trimester are reviewed, with a particular focus on labor and delivery planning and common obstetric complications. Diagnostic testing and the use of medications in pregnancy and lactation are discussed in detail.


Hematologic disease is common among reproductive age women and therefore hematologic conditions are seen frequently in pregnancy. Most disorders can be safely managed through parturition, with the result of a healthy mother and child. Although the risks of pregnancy and impact of disease will differ based on the condition present, the general approach to the gravid patient remains the same. The care plan should address how pregnancy affects her disease, and how the disease affects pregnancy. Discussions with the pregnant woman should include the impact of her condition on common obstetric complications, medication concerns, labor and delivery management, and risks of heritability.


How the disease affects pregnancy


The effect of hematologic disease on pregnancy varies by trimester. Most women with medical conditions should be advised that they will have increased maternal and fetal surveillance during their pregnancies. This may involve increased visits, laboratory draws, or fetal evaluation. In addition, there may be extensive planning for labor and delivery.


The First Trimester


Women with bleeding disorders are at increased risk for obstetric complications in the first trimester of pregnancy. Embryo implantation, miscarriage, molar and ectopic pregnancy are all associated with bleeding. Miscarriage (loss before 24 weeks’ gestation) complicates 10% to 15% of pregnancies. Bleeding associated with miscarriage may be heavy, depending on the gestational age at the time of loss. Some women choose to pass early pregnancies at home, whereas others prefer to have surgical evacuations by vacuum aspiration or dilation and curettage. Because they are at increased risk of uncontrolled hemorrhage, women with bleeding disorders are typically best served by a surgical evacuation, which requires careful surgical planning. Molar pregnancies are rare, occurring in approximately 0.1% of pregnancies. Bleeding is a hallmark of molar pregnancy, and surgical evacuation is required.


The Second Trimester


Women with hematologic disorders may desire invasive testing for aneuploidy in the second trimester. Options include chorionic villus sampling (CVS) and amniocentesis. In CVS, a biopsy of the placenta is taken between 11 and 14 weeks’ gestation. This procedure may entail more risk for women with bleeding disorders and special precautions such as pretreating with desmopressin acetate (DDAVP), or blood products should be considered. Amniocentesis is associated with a lower risk for bleeding; however, the risks and benefits of the procedure should still be addressed with the patient and her obstetrician. Prophylactic anticoagulation is often held for 1 day before either procedure, particularly CVS, depending on provider preference.


The Third Trimester


A small number of women experience complications that put their health, or the health of their fetus, at risk. These typically occur in the third trimester. Three of the most common, and those most likely to be affected by hematologic disease, are placental abruption, placenta previa, and preterm labor. A careful obstetric history may help to stratify the risks, because complications frequently recur. These complications are often unpreventable and of sudden onset, a carefully documented emergency management plan is essential.


Placental abruption


Placental abruption is defined as a separation of the placental bed from the uterine wall. An abruption may be characterized by light bleeding, or by major obstetric hemorrhage requiring emergent delivery. Rates of abruption vary by population from 0.7% to 1.4%. The incidence is higher in women with risk factors such as smoking, hypertension, or prior abruption. Bleeding disorders and anticoagulation may substantially increase the risk to both mother and fetus in this setting. All pregnant women with bleeding disorders should have a plan in place that outlines how to manage unexpected bleeding.


Abnormal placentation


Placenta previa describes the situation in which the placenta is implanted close to, or overlying, the uterine cervix, whereas placenta accreta describes invasion of the placenta into the uterine wall. The risks of placenta previa and accreta increase with greater numbers of cesarean deliveries or uterine surgeries. Previa is associated with a risk of bleeding from unprotected placental vessels, which often leads to hospitalization and preterm birth. For most women without a prior cesarean delivery, a placenta previa seen early in pregnancy spontaneously resolves as the uterus grows during gestation. Placenta accreta almost universally necessitates hysterectomy at the time of delivery.


Preterm labor


Preterm labor affects approximately 13% of the population, with more than 70% of these babies born between 34 and 36 weeks’ gestation. Preterm contractions without labor are even more common. The diagnosis of preterm labor is often challenging to make. Although some women presents in labor and subsequently deliver within a few hours, others report contractions without cervical change for several days before cervical dilation. The unpredictable nature of obstetrics makes the management of patients with significant hematologic disease challenging. For example, for women maintained on therapeutic anticoagulation, there may be inadequate time for anticoagulation to be reversed, preventing the patient from getting regional anesthesia in labor, and increasing the risks of bleeding at delivery. Conversely, women with idiopathic thrombocytopenic purpura (ITP), who are often not treated until later in the pregnancy, may miss the opportunity for therapy before delivery, increasing their risks of bleeding.


Tocolytic medications including nifedipine, terbutaline, indomethicin, and magnesium sulfate are often given in an effort to halt preterm labor. Tocolysis is controversial, although many believe that it may arrest labor for 48 hours, the time period in which steroids are given to induce fetal lung maturity. For all of these reasons, it is important to make careful delivery plans early in gestation. These plans may be complex, making the accurate diagnosis and management of preterm labor critical.


Labor and Delivery: Specific Concerns


Many women who pass easily through their pregnancies are surprised at the level of planning and risk that delivery entails. Coordination between multiple teams is often required, including obstetrics (generally maternal fetal medicine specialists, if available), hematology, anesthesia, blood bank, and nursing, and it is never too early to start planning. As discussed earlier, many women have unexpected pregnancy complications, including bleeding and preterm labor, and a carefully laid plan can prevent substantial maternal and fetal morbidity.


A detailed labor and delivery plan should discuss mode of delivery, anesthesia concerns, and specific risks to the mother or fetus related to the hematologic disorder in question. In specific cases, it may also be helpful to provide the patient with a copy of her delivery plan, particularly if she lives at distance from the hospital or is planning to travel.


Pregnant women with medical disease are often advised to schedule delivery either by induction of labor or cesarean section, to optimize safety surrounding the delivery or to allow postpartum therapies that are contraindicated during pregnancy. Most of these deliveries can be undertaken in the 39th week, when fetal outcomes are optimized, but before many women have entered into spontaneous labor. There are some cases in which delivery before 39 weeks is indicated, most notably when maternal medical needs outweigh the small risks of late preterm birth to the fetus. The earlier in gestation that induction of labor is undertaken, the more likely that the uterine cervix is unfavorable, which increases the duration of the induction.


Both induction of labor and cesarean delivery carry significant risks. There are few strict indications for cesarean section. Inarguable maternal indications include a history of several different types of uterine surgery or abnormal placentation (placenta previa or accreta). Women may also have uncommon medical or physical conditions for which cesarean delivery is preferred, such as an inability to obtain lithotomy position, or pelvic contractures. Strict fetal indications include malpresentation (the presenting fetus is persistently breech or transverse) and some fetal anomalies, for example neural tube defect. Cesarean delivery is also commonly performed for several other reasons, including maternal request and suspected fetal macrosomia. Indications for cesarean delivery must be individualized, but most women are candidates for vaginal birth.


Induction of labor is achieved through use of vaginal prostaglandins, mechanical dilation, and intravenous (IV) oxytocin. During the period of cervical ripening, most women are not yet in labor, and may not be for another 24 hours or longer. For those with a prior vaginal birth, delivery may be attained in under one day. Without a prior vaginal birth, induction is less predictable and may take several days, depending on provider and patient tolerance. Some women experience minor bleeding during cervical dilation; however, most bleeding occurs around delivery. Bleeding continues until vaginal lacerations are repaired and uterine tone is achieved, typically within 40 minutes after the infant’s birth. Typical blood loss for vaginal birth is less than 500 mL.


Cesarean section accounts for more than 30% of deliveries. The operation is typically performed through a transverse lower abdominal skin incision, and transverse uterine incision. The duration of surgery is commonly 30 to 60 minutes, with blood loss under 1000 mL. The procedure can be scheduled at the convenience of the obstetric and medical teams, often making it an appealing option. Nonetheless, cesarean delivery carries greater maternal risks of hemorrhage and infection than does vaginal delivery, and increases the chance of abnormal placentation in a future pregnancy. With each surgery, these risks rise. Incidence of thromboembolic disease is also increased for 6 weeks postpartum. For all of these reasons, cesarean delivery should only be performed with appropriate indications.


For both vaginal birth and cesarean delivery, careful consideration must be given to the management timeline. At any point during a labor induction, an emergent delivery might become necessary. Anticoagulation is held during labor for all but the most critical indications (eg, artificial heart valves, severe prothrombotic states). For that reason, some would recommend a cesarean delivery to limit the time off anticoagulation; however, surgery increases the risk of postpartum clot formation compared with vaginal delivery. In addition, vaginal delivery is less likely to be complicated by postdelivery bleeding that would be worsened by anticoagulation. In a carefully monitored setting, with appropriate anesthesia and blood bank support, women may be anticoagulated during labor, with anticoagulation held at delivery and in the immediate postpartum period. This strategy should be reserved for the most critically ill patients who have a life-threatening risk of thrombosis.


A woman who requires platelet or other transfusion support would have a different scenario. For that patient, consideration must to given to frequency of laboratory evaluation, and timing and indications for transfusion. If the patient is to be induced, should transfusions begin on admission, in the active phase of labor, or when delivery is imminent? For the patient requiring platelets, should transfusions be initiated if platelets decline, or when they reach a certain threshold? Every patient should also have an emergency backup plan, in case of complications such as a transfusion reaction or the need for an unscheduled cesarean delivery.


The importance of communication among various members of the team cannot be overstated. Before delivery, it is helpful to have a detailed discussion regarding what complications from the pregnancy and disease may be anticipated, as well as any known complications of therapy. In addition, definition of critical laboratory values and an algorithm with which to treat them are essential. If an induction is planned, clear communication with the blood bank to ensure adequate stocking of the appropriate products and preparation of medications is also of key importance. If adequate products cannot be assured, consideration should be given to transfer of the patient to a facility with appropriate resources.


Anesthesia


Anesthesia is an important component of labor and delivery planning. Many women undergoing spontaneous or induced labor request epidural anesthesia, and most uncomplicated cesarean deliveries are performed under spinal anesthesia. There is controversy in the anesthesia literature regarding safe platelet levels for regional anesthesia. Although some sources suggest platelets greater than 100,000 minimize the risk of epidural hematoma, others report safe placement with platelets as low as 69,000. At our institution, platelets of 70,000 are required for both regional anesthesia placement and removal of the epidural catheter. Additional options for pain control during a vaginal birth include intravenous or intramuscular narcotics, and for cesarean delivery, general anesthesia. General anesthesia increases the likelihood of need for neonatal resuscitation, including intubation.


Postpartum hemorrhage


Postpartum hemorrhage (PPH) is defined as blood loss greater than 500 mL for a vaginal delivery or 1000 mL for a cesarean delivery. Rates of PPH vary by study, but have been reported to be as high as 19% in a low-risk European population. Many healthy young women tolerate the increased blood loss well. Almost all hemorrhages occur within 24 hours of delivery (early PPH), with a small minority occurring 24 hours to 6 weeks after delivery (late PPH). Bleeding may be brisk, because between 500 and 800 mL of blood pass through the term uterus each minute. Given the frequency of PPH, the unique risks hemorrhage may hold for the patient with hematologic disease need to be considered, as well as parameters for transfusion or medication therapy.


Fetal Concerns


An important consideration when caring for pregnant women with medical disease is the risk that the fetus will either inherit the disease in question, or be affected by the mother’s condition. Any woman with a potentially heritable disorder should be offered genetic counseling before pregnancy or early in gestation, because genetic testing for the fetus may be possible. Understanding fetal risk is also essential for delivery planning. If the fetus has a known or suspected bleeding disorder, or, as in ITP, there is concern for neonatal thrombocytopenia, operative vaginal delivery (forceps or vacuum-assisted delivery) is contraindicated, as is fetal monitoring using a scalp electrode. In these infants, profound thrombocytopenia may develop in the first days of life, therefore communication with the pediatric team is essential.

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Sep 16, 2017 | Posted by in HEMATOLOGY | Comments Off on Hematologic Disease in Pregnancy: The Obstetrician’s Perspective

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