One of the many early physiological adaptations of
pregnancy involves changes in the coagulation system,
which promote coagulation and impair fibrinolysis. The
physiological goal is to prepare for the haemostatic
challenge of delivery. A ‘side effect’ of this change is an
increased risk of thrombosis. All pregnant women are
therefore at risk of thrombosis, compared with non-
pregnant women. This risk is manifest from early in the
first trimester until 4−6 weeks post partum.
PHYSIOLOGICAL CHANGES IN THE
COAGULATION SYSTEM DURING PREGNANCY
These changes, which may not completely return to baseline until more than 8 weeks post partum, begin at
RISK FACTORS FOR VTE IN PREGNANCY
In some women the risks are increased further
because they have one or more additional risk
So pregnant women should have a risk assessment
for VTE to include the risk factor as listed.
This risk is not static and should be reconsidered in
A careful hx should be taken from the woman of
any prior or family hx of thromboembolic events.
Type Signs and Symptoms
Pulmonary embolism • Dyspnea
• Pleuritic chest pain
• Cyanosis/hypoxia in massive PE
• +/- symptoms or signs of DVT
Deep vein thrombosis • DVT in pregnancy usually proximal
• Unilateral leg pain/tenderness
• Swelling in an extremity
• Increase calf/thigh circumference
• Increased temperature
• Prominent superficial veins
• Pitting edema
• DVT: swelling and lower leg discomfort are
not unusual in a normal pregnancy. Other
possibilities include muscle strain, a ruptured
Baker’s cyst, cellulitis, superficial
thrombophlebitis, ruptured plantaris tendon
• PE: potentially extensive but specifically rule
out chest infection and an intra-abdominal
bleed (look for abdominal signs, shoulder tip
pain from diaphragmatic irritation and a low
Massive life treatening PE
• Management by an experienced multidisciplinary team
involving senior obstetrician,physicians and radiologist
for collapsed,shock patient.
• An urgent portable echocardiogram should be
arranged within one hour presentation.
• Immediate thrombolysis should be considered when
massive PE is confirmed or extensive circumstance
• IV unfractionated heparin.
• In a woman with a past history of VTE or with a known inherited
thrombophilia, it is best to refer her prior to a planned pregnancy
for optimum prophylaxis throughout the pregnancy.
• Medical anticoagulation is the treatment of choice for acute VTE.
Subsequently, surgical interventions may be considered
• Anticoagulation is by far the most common treatment option.
Heparin is the most frequently used drug, being non-toxic to the
fetus (it does not cross the placental barrier). However, its main
disadvantages are that it has to be parentally administered and, in
the long-term, may give rise to heparin-induced osteoporosis and
thrombocytopenia. In some patients, it can also provoke a painful,
localized allergic reaction on administration.
• Warfarin is the other treatment option in the postnatal patient but
it must be avoided antenatally, as it is teratogenic and can also
cause placental abruption and fetal/neonatal hemorrhage.
• In clinically suspected DVT or PE, treatment with unfractionated
heparin or LMWH should be given until the diagnosis is excluded.
There are several different types of heparin to choose from:
• LMWH: this is the drug of choice. It has been shown to be
more effective than unfractionated heparin with lower
mortality and fewer hemorrhagic complications in the
initial treatment of DVT in non-pregnant subjects.
• Intravenous unfractionated heparin: this is an extensively
used drug in the acute management of VTE, particularly
massive PE with cardiovascular compromise
• Subcutaneous unfractionated heparin: this has been shown
to be as effective as the intravenous form.
• Additionally, the leg should be elevated and a graduated
elastic compression stocking applied to reduce edema.
Mobilization with graduated elastic compression stockings
should be encouraged.
• Heparins are the maintenance treatment of choice.
• Subcutaneous LMWH appears to have advantages over aPTT-
monitored unfractionated heparin in the maintenance treatment of
VTE in pregnancy. Women should be taught to self-inject and can then
be managed as outpatients until delivery.
• If unfractionated heparin is used, monitor the platelet count at least
every other day for the first 14 days or until treatment is stopped
(whichever comes first).
• Seek specialist advice if the patient develops heparin-induced
thrombocytopenia or a heparin allergy and requires continuing
anticoagulant therapy. She should be managed with the heparinoid,
danaparoid sodium or fondaparinux, under specialist supervision.
• When the patient thinks she is going into labour, she should stop injecting and get
in touch with the delivery ward staff that will manage the anticoagulation
throughout labour and immediately post-delivery. Alternatively, planned elective
induction of labour or caesarean section at least 12 hours after prophylactic-dose
LMWH or 24 hours after therapeutic-dose LMWH can be considered. As these
patients are at high risk of hemorrhage, they will be managed with intravenous
unfractionated heparin throughout this time. Regional anaesthetic or analgesic
techniques should not be undertaken until at least 24 hours after the last dose of
• Depending on the patient's individual circumstances, she may be managed with
ongoing heparin treatment or warfarin postpartum. If she opts for warfarin, this
needs to be avoided until at least day three postpartum with an INR check at day
two of warfarin treatment: aim for an INR between 2 and 3. Continue heparin
treatment until there have been two successive readings of an INR >2. Although
these drugs are detectable in breast milk, all are safe for use during breast-feeding
because warfarin metabolites are inactive and heparin is not absorbed through the
• Postnatal review for women who develop VTE during pregnancy or the puerperium
should, whenever possible, be at an obstetric medicine clinic or a joint obstetric
• In theory, therapy should be continued for six
months as would be the case for non-pregnant
patients. However, the postpartum state is a
period of physiological fluctuation of coagulation
factors. Therefore, current advice is to continue
therapy for at least 6-12 weeks postpartum or
until at least three months of therapy have been
completed. At that point, the patient should be
assessed for the presence of ongoing risk factors
for a VTE prior to making the decision to stop
Guidance from the Royal College of Obstetricians and Gynecologists’
• Regardless of their VTE risk, dehydration and immobilization of the patient should be avoided
• Women at high risk of VTE in pregnancy should be offered pre-pregnancy counseling and a
prospective management plan for thromboprophylaxis in pregnancy. Those who become
pregnant before receiving such counseling should be referred to a nominated expert early in
• All women with previous VTE should receive postpartum prophylaxis, as this is the time of
• In addition, women whose original VTE was unprovoked, idiopathic or related to estrogen, or
who have other risk factors, a family history of VTE in a first-degree relative or a documented
thrombophilia require LMWH antenatally and for six weeks postpartum.
• Women with recurrent VTE may already be on warfarin. They should be advised to stop
warfarin and change to LMWH as soon as pregnancy is confirmed, ideally within two weeks
of the missed period and before the sixth week of pregnancy. Women not on warfarin should
be advised to start LMWH as soon as they have a positive pregnancy test.
• Women with asymptomatic inherited or acquired thrombophilia only, may be managed with
close surveillance antenatally and be considered for LMWH for at least seven days
postpartum. Exceptions are women with antithrombin deficiency, those with more than one
thrombophilic defect (including homozygosity for factor V Leiden) or those with additional
risk factors where antenatal prophylaxis should be considered.
• Women taking LMWH should be advised that, if they bleed
vaginally or contractions begin, they should not inject any further
doses. They should be assessed in hospital and further doses be
prescribed by medical staff.
• All women with obesity (BMI greater than 40 kg/m2) should be
considered for prophylactic LMWH for seven days after delivery.
Other postnatal risks include prolonged labour, immobility,
infection, hemorrhage and blood transfusion.
• All women who have had an emergency Caesarean section should
be considered for LMWH for seven days after delivery. All women
who have had an elective caesarean section who have one or more
additional risk factors should be considered for LMWH for seven
days after delivery.
• In addition, properly applied graduated compression stockings are
recommended for women travelling long-distance for more than
four hours, women who are still outpatients but have prior VTE
(usually combined with LMWH), women who are hospitalized and
have a contra-indication to LMWH and those who are hospitalized
post-caesarean section (combined with LMWH) and considered to
be at particularly high risk of VTE.