DVT in Pregnancy: Precautions
If a woman was treated for DVT or pulmonary embolism in one pregnancy, does she need to take any special precautions in future pregnancies?
Opinions on this differ. There is consensus that any woman with a history of pulmonary embolism in the past should start preventative heparin injections as soon she finds out she is pregnant. This advice is also relevant for those considered to be high-risk.
The high-risk group includes those with thrombophilia syndrome and those who have a history of two or more episodes of thrombosis in the past. This is regardless of whether the episodes occurred during pregnancy or not.
For those who are deemed to be low-risk, the policy is less clear-cut and the attending doctor will, in most cases, decide on an individual basis.
For an expectant mother with a history of thrombosis, what constitutes low-risk?
If there is only one episode of uncomplicated DVT in the mother's past history, it is considered low-risk. However, if there is an additional risk factor, such as obesity, smoking, or she has had several children (multiparity), the attending doctor may advise the use of heparin as a preventative measure.
Are there any special precautions or measures that should be taken during labour and delivery?
All high-risk patients who will already be on heparin during pregnancy have to carry on during labour and delivery, with some minor scheduling adjustments.
For low-risk patients, who may not have been on any preventative treatment, many experts agree that a short course commenced at the onset of labour and continued for a few weeks postnatally is a good idea. Again, this has to be individualized.
Post-delivery, the mother may opt to switch from injections to warfarin tablets, or she may decide to carry on with injections.
What if delivery is by caesarean section?
In this case, the advice is clear. Both low- and high-risk patients are given heparin. Operative delivery (caesarean section) is a recognised risk factor for thrombosis in its own right and anybody with a previous history has to be protected.. This preventative measure is extended to those with no previous history of thrombosis but who have an independent risk factor, such as being overweight. In some units, this is given to all mothers undergoing a caesarean section.
Thrombosis: Treatment post-delivery
Why is treatment continued after delivery?
Because the risk posed by pregnancy does not disappear immediately after delivery. It tends to subside slowly and the immediate postnatal period is a risky period. The six to eight weeks of treatment is arbitrary, because it has always been difficult to know when it is entirely safe to stop altogether; the figure has more to do with tradition than science.
Does the mother have the option of warfarin after delivery?
A week after delivery, the treatment may be changed from injectable heparins to oral warfarin tablets. The concern about the risk of warfarin to the baby is, of course, no longer there.
Warfarin is also safe with breast-feeding. However, not every patient is keen to switch to warfarin. Warfarin medication necessarily entails regular and frequent blood tests to ensure that the correct dose is being taken. For heparin this is not necessary.
Since heparin is self-administered, many mothers consider this to be a significant advantage, which avoids the inconvenience of frequent hospital visits. This is now reinforced by the availability of once-daily injections. Ideally, mothers are given the options in the postnatal period.
So, there is no problem with breast-feeding for both warfarin and heparin?
That is correct. The low molecular-weight heparins are also safe.