Antiepileptic of choice in pregnant lady?

Drugs for which there is good data include:

Carbamazepine - generally perceived as the safest anti-epileptic agent in pregnancy. In all cases, patients should be assured that the chance of abnormality is low

complications include:
neural tube defects - 1% risk
hypospadias
a higher frequency of major malformations, particularly heart defects, neural tube defects and hypospadias, has been reported in children of mothers who took carbamazepine during pregnancy than in either children of mothers without epilepsy (e.g. 5.3% vs. 2.3%) or children of women whose epilepsy was treated with phenytoin.


Phenobarbitone
major malformation rate of 2.4-6.5% has been reported among pregnancies with phenobarbital exposure which, in some cases, was comparable to the risks seen with other antiepileptic drugs or among the general population.
common malformations are cleft lip and palate, and congenital heart disease, especially septal defects
primidone is largely converted to phenobarbital and this is probably responsible for its antiepileptic action
a major malformation rate of 5.7-14.3% has been reported among pregnancies with primidone exposure (vs. no drug exposure OR up to 5.3, p=0.029)



Phenytoin - this drug in particular is implicated in congenital malformation caused by antiepileptics; the incidence of fetal malformations is 1.8% in patients taking this drug compared to 0.7% in the normal population. Common malformations are cleft lip and palate, and congenital heart disease, especially septal defects.



Sodium valproate - associated with a 1.5% risk of neural tube defects. This may be attributed in part to its effect in reducing serum folate, itself thought to be protective against neural tube defects.
other abnormalities include:
-hypospadias
-heart defects
-craniofacial and skeletal anomalies
-developmental delay - there is evidence from two retrospective studies of an association between in-utero exposure to sodium valproate and developmental delay, fetal exposure with valproate is associated with lower IQ scores in childhood.


Medscape says-- 
Current evidence suggests that women taking valproate in the first trimester run the highest risk for congenital malformations, an effect that is probably dose-related. Furthermore, children who are exposed to valproate prenatally had impaired fluency and originality compared with children who were exposed to carbamazepine and lamotrigine. Phenytoin and phenobarbital should also be avoided to prevent adverse cognitive outcomes.