Sir, the use of local anaesthetics (LA) in the treatment of pregnant women is a difficult area as there is an absence of evidence because of ethical constraints preventing randomised controlled studies. Current advice is to avoid non-essential dental treatment until after pregnancy, and where treatment is required to aim to perform it in the second trimester. The reason for this is that in the first trimester organogenesis occurs and small degrees of insult may lead to significant damage to the developing foetus.

The difficulty with comparing the use of LA as opposed to not using them is further complicated because it is usually an adjunct to carrying out a secondary procedure, so a control group not having treatment under LA would also include the group that did not have actual treatment. Therefore, any complications noted in the mother and child would include some of the complications of lack of treatment of the dental problem (eg caries, dental abscess etc).

A recent article reported a prospective, comparative observational study following 210 pregnancies exposed to dental LA in the first trimester compared with 794 pregnancies not exposed to teratogens. The rate of major anomalies was not significantly different between the groups and there was no difference in the rate of miscarriages, gestational age at delivery, or birth weight.1 The results suggest that use of dental LA, as well as dental treatment, during pregnancy does not represent a major teratogenic risk and there seems to be no reason to deny pregnant women these interventions.

Currently, the most widely used local anaesthetic agent in dentistry is lidocaine, which was originally marketed in 1948.2 LA cross the placenta in varying degrees. The concentration in the foetal circulation in descending order are by prilocaine, lignocaine and bupivacaine.3,4 In addition the dose of adrenaline used in lignocaine is so low that it is unlikely to significantly affect uterine blood flow and the benefits of its incorporation justify its use.5,6