August 26, 2011.
All women undergoing cesarean
delivery should undergo thromboembolism prophylaxis at the time of delivery,
according to an American College of Obstetricians and Gynecologists (ACOG)
Practice Bulletin published in the September 2011 issue of Obstetrics &
Gynecology. The new bulletin, entitled "Thromboembolism in Pregnancy," aims
to summarize evidence and recommendations regarding risk factors, diagnosis,
management, and prevention of thromboembolism, especially venous
thromboembolism (VTE), in pregnancy.
"VTE is a major contributor to
maternal mortality in this country," coauthor Andra H. James, MD, said in a
news release. "The risk of VTE is increased during pregnancy and the
consequences can be severe. The recommendations explain how to monitor women
for these events, address certain risk factors, and treat suspected or acute
cases of VTE. It's important for ob-gyns to adopt these recommendations to
help reduce maternal deaths."
Compared with nonpregnant women,
pregnant women have a 4-fold to 5-fold increased risk for thromboembolism.
About 80% of thromboembolic events during pregnancy are venous, with
pulmonary embolism and other VTE responsible for 1.1 deaths per 100,000
deliveries, or 9% of all maternal deaths in the United States.
the developing world, the leading cause of maternal death is hemorrhage;
however, in developed nations, where hemorrhage is more often successfully
treated and prevented, thromboembolic disease is one of the leading causes
of death," the Practice Bulletin authors write. "The prevalence and severity
of this condition during pregnancy and the peripartum period warrant special
consideration of management and therapy. Such therapy includes the treatment
of acute thrombotic events and prophylaxis for those at increased risk of
Physiologic and anatomic changes during pregnancy
increase the risk for thromboembolism. Hypercoagulability, increased venous
stasis, decreased venous outflow, uterine compression of the inferior vena
cava and pelvic veins, reduced mobility, and changes in levels of
coagulation factors normally regulating hemostasis all result in an
increased thrombogenic state. Risk for deep vein thrombosis during pregnancy
is greatest in the left lower extremity.
Other risk factors for VTE
unrelated to pregnancy include a personal history of VTE, thrombophilia,
obesity, hypertension, and smoking.
The only specific Level A ACOG
recommendation (based on good and consistent scientific evidence) is that
compression ultrasonography of the proximal veins is the recommended initial
diagnostic test when signs or symptoms suggest new onset deep vein
Level B ACOG recommendations
and conclusions (based on limited or inconsistent scientific evidence)
include the following:
Heparin compounds are the preferred
anticoagulants in pregnancy.
To minimize postpartum bleeding
complications, a reasonable strategy is to resume anticoagulation therapy no
sooner than 4 to 6 hours after vaginal delivery, or 6 to 12 hours after
Warfarin, low molecular weight heparin (LMWH), and
unfractionated heparin are compatible with breast-feeding because they do
not accumulate in breast milk and do not lead to anticoagulation in the
Level C ACOG recommendations (based primarily on consensus
and expert opinion) include the following:
Women with a history of
thrombosis who have not been thoroughly evaluated for possible underlying
causes should receive testing for antiphospholipid antibodies, as well as
for inherited thrombophilias.
For women with acute thromboembolism during
the current pregnancy, or for those at high risk for VTE, including women
with mechanical heart valves, therapeutic anticoagulation is recommended.
For women in whom restarting anticoagulation is planned after delivery,
pneumatic compression devices should be left in place until the woman is
ambulatory and anticoagulation therapy is resumed.
In the last month of
pregnancy, or sooner if delivery appears imminent, women receiving either
therapeutic or prophylactic anticoagulation may be converted from LMWH to
unfractionated heparin, which has a shorter half-life.
should be withheld for 10 to 12 hours after the last prophylactic dose of
LMWH, or 24 hours after the last therapeutic dose of LMWH.
For all women
not already receiving thromboprophylaxis, placement of pneumatic compression
devices before cesarean delivery is recommended. However, an emergency
cesarean delivery should not be delayed for the placement of compression
"Cesarean delivery is an independent risk factor for
thromboembolic events — it nearly doubles a woman's risk," Dr. James said.
"Fitting inflatable compression devices on a woman's legs before cesarean
delivery is a safe, potentially cost-effective preventive intervention.
Inflatable compression sleeves should be left in place until a woman is able
to walk after delivery or — in women who had been on blood thinners during
pregnancy — until anticoagulation medication is resumed."
performance measure, ACOG proposes using the percentage of patients
evaluated for risk factors for thrombosis at the beginning of pregnancy,
during pregnancy, and at the time of delivery.
"Because half of
VTE-related maternal deaths occur during pregnancy and the rest during the
postpartum period, ongoing patient assessment is imperative," Dr. James
concluded. "While warning signs in some women may be evident early in
pregnancy, others will develop symptoms that manifest later in pregnancy or
after the baby is born."
Obstet Gynecol. 2011;118:718-729.