A known or even presumed pregnancy is a fundamental part of the medical history. In the dental field, this condition is in fact a relative contraindication to elective therapies. The first trimester is considered the most sensitive period, the beginning of the second the safest.

The decision to perform a treatment thus derives from an assessment of the cost-benefit ratio.  Nonetheless, it is generally advisable to contact the attending physician (gynaecology and obstetrics specialist) during the planning of treatment whenever it is deemed necessary, or if the patient reports complications during previous pregnancies.

Is local anaesthesia contraindicated in pregnancy?

In principle, there is no actual contraindication to local anaesthesia in pregnancy. There are however cautions regarding the dosage and the method of administration — in common with various categories of dental patients, though with slight variations — and, specifically, regarding the use of certain active ingredients.

The classification provided by the United States Food and Drug Administration is used. This divides the various drugs on the basis of the scientific evidence for the potential risk to the product of conception.

Local anaesthetics in dentistry: risk classes

There are five classes: ranging from A (safe compound: controlled studies do not show any risk) to D, where an increasing risk is observed. To these is added class X, which contains all the drugs contraindicated in pregnancy. For completeness, it should be noted that the FDA has updated its classification, replacing it with the Pregnancy and Lactation Labeling (Drugs) Final Rule from 2015, i.e., the year following the last update of the ministerial guidelines.

Lidocaine, for topical or local use, is in class B, and is therefore assessed as safe for dental use. It is also considered safe in breastfeeding.

However, the compounds which are perhaps most widely used as local anaesthetics, i.e., articaine, bupivacaine and mepivacaine, are all included in class C. Their use should therefore be carefully assessed and they are only recommended if the expected benefit for the patient exceeds the potential risk. In addition, the American Academy of Pediatrics (AAP) does not recommend the use of articaine during breastfeeding.

As regards the use of vasoconstrictors, epinephrine was classified as risk C by the FDA. According to the ministerial guidelines, if care is taken to avoid intravascular injection, a total of 5 cartridges with an adrenaline concentration of 1:100,000 (or 10 with 1:200,000) can be administered to a healthy pregnant woman. As previously mentioned, one aspect requiring particular care is the assessment of the potential toxicity of an absolute overdose (an excessive number of cartridges) or a relative overdose (rapid intravenous injection or injection into hyperaemic tissue).

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