There has been a decline in prescribing of the older AEDs namely carbamazepine and sodium valproate since 1994 whereas prescribing of lamotrigine, a newer AED, has increased five-fold since 2000. Amongst pregnant women with epilepsy, those receiving prescriptions more often prior to pregnancy were more likely to continue receiving AED prescriptions during pregnancy. Furthermore, those receiving lamotrigine were less likely to stop in pregnancy compared to women prescribed sodium valproate. Pregnancy was a determinant for the discontinuation of AED prescribing, in particular for women with bipolar disorder or depression. The majority of pregnant women prescribed AEDs for indications other than epilepsy and bipolar disorders discontinued prescriptions by six weeks into pregnancy.
The secular changes in prescribing habits observed in this study were similar to those seen in other countries. A fall in the use of carbamazepine and sodium valproate and a rise in lamotrigine were observed in the Australian Register of Antiepileptic Drugs in Pregnancy, the European and International Registry of Antiepileptic Drugs in Pregnancy and the Neurodevelopmental Effects of Antiepileptic Drugs study groups 
. Sodium valproate and carbamazepine have been linked to severe teratogenic effects when taken in pregnancy 
. Initially their prescription in pregnancy decreased over time. However, it is noticeable that since 2004 prescribing of these drugs in pregnancy remained relatively constant and that by 2009 they were still the second and third most commonly prescribed AED in pregnancy. The reasons for increased prescribing of lamotrigine are unclear – no formal guidance has been issued indicating the safety of lamotrigine. Recent evidence suggests no greater risk of MCMs is associated with lamotrigine when compared to untreated pregnancies in women with epilepsy 
. However, one study does report an increased risk of isolated cleft palate/lip in lamotrigine exposed babies compared to the general population and the BNF states lamotrigine is associated with increased teratogenicity 
. The guidance from the NICE is inconsistent. It states lamotrigine should not be prescribed to pregnant women with bipolar disorder because of the risk of harm to the fetus, but such advice is not provided in the guidance for women with epilepsy 
. Our results on secular prescribing trends and discontinuation of specific AEDs in pregnancy suggest that many healthcare professionals are selectively prescribing lamotrigine. Further data are required on the risks and benefits of prescribing lamotrigine in pregnancy.
To our knowledge, no other study has examined the discontinuation of AEDs in pregnancy. Our study showed that pregnant women were more likely to stop receiving AED treatment compared to non-pregnant women also receiving AEDs. This behaviour has been reported for other medications prescribed to pregnant women as they were concerned about the effect the drugs would have on the fetus 
. Our data cannot explain the behaviour, as we are unable to determine if it was the GP, the woman or both who were choosing to stop AEDs. We can only observe that women in pregnancy stop AEDs sooner than when they are not pregnant. Women with epilepsy behaved differently from those with bipolar disorder or depression. We separated these two groups since we had observed a similar steep decline in antidepressant prescribing in pregnancy in a previous study 
. Pregnant women with epilepsy were twice as likely not to receive AEDs whilst this was more than three-fold in pregnant women with bipolar disorder or depression. We found a third of the women who were prescribed AEDs for bipolar disorders continued to be prescribed other alternative drugs such as antidepressants and antipsychotics.
Women with epilepsy who received frequent prescriptions prior to pregnancy were less likely to stop these drugs in pregnancy. These women may be those with a more severe form of the disease which requires regular consultation with their GP. It may also be that women receiving frequent AED prescriptions are those that are more likely to adhere to their medication.
We found no significant associations for the discontinuation of AEDs amongst pregnant women with bipolar disorder but we were limited by a small sample size.
Stopping medication in pregnancy is a choice that women should make rather than being forced to continue treatment against their wishes. The issue is whether women are fully informed before they make this choice. A recent survey of women with epilepsy highlighted failures in women receiving appropriate pre-conception counselling on the risks AEDs pose to the unborn child, despite the recommendation by NICE for this to be conducted for all women with epilepsy of childbearing potential 
. This suggests that women could be making decisions to stop or continue AED therapy without fully understanding the risks and benefits of their actions.
Healthcare professionals need to keep up to date with the latest information on the risks of AEDs in pregnancy 
. There is lack of information on the relative risks between AEDs – a common choice healthcare professionals and women have to make. Research efforts in this area must therefore continue and must be more robust in order for stronger inferences to be made and clearer guidance to be provided.
The main strength of our study is the large sample size of women taking AEDs. Although this study is restricted to primary care, it captures the prescribing patterns for women who attend secondary and tertiary care. Neurologists and psychiatrists most often initiate this drug treatment, but in the UK the prescribing is then passed on to GPs who are wholly responsible for long term prescribing. Therefore the trends observed in this study are representative of most pregnant women taking AEDs.
The major limitation of the study is the verification of adherence to prescribed treatment. However, a recent study of UK prescriptions dispensing showed that over 98% of AEDs prescribed in general practice were dispensed 
We found a shift in the prescribing of AEDs in pregnancy from older to newer ones, in particular there has been a five-fold increase in the prescribing of lamotrigine since 1994. Pregnancy was a strong factor for the cessation of AED prescriptions, particularly in women with bipolar disorder. There are risks and benefits associated with the (dis)continuation of AEDs in pregnancy and it is important these are balanced to allow women and healthcare professionals to make an informed decision on whether to continue treatment in pregnancy. Further research is urgently needed to firmly establish the safety of AEDs in pregnancy, particularly for the increasingly prescribed AED, lamotrigine.