Introduction:
Pregnancy is a unique experience in a woman's life. Because the mother's health is directly related to the health of the growing fetus, pregnant women must remain in good health. Many pregnant women require dental treatment due to poor oral hygiene during pregnancy. Often these dental professionals are hesitant to provide, and most pregnant women are reluctant to receive, dental treatment during pregnancy. The administration of local anesthetics (LA) in the treatment of pregnant women is a challenging area to study because of ethical constraints that prevent randomized controlled trials. Should avoid non-essential dental procedures till childbirth; if necessary, treatment should be performed in the second trimester. The possible explanation is that organogenesis occurs during the first trimester, and even minor insults can cause significant harm to the developing fetus.
Alterations in the oral environment and excessive food consumption during pregnancy can increase the risk of dental caries, whereas hormonal changes can increase the likelihood of periodontal diseases. In addition, poor oral health management increases the chance of preeclampsia, preterm birth, and low birth weight. Often these dental treatments require local anesthesia, and drugs administered by the mother can theoretically be transferred to the fetus via the placenta and affect the fetus. As a result, when performing a treatment on a pregnant woman, the effects of any drug given to the pregnant woman must be considered for both the mother and fetus.
What Are the Physiological Changes That Occur During Pregnancy?
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When a fertilized egg implants on the uterine wall, pregnancy begins. The mother's physical function completely changes as the pregnancy progresses.
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These include a variety of physiological changes required for fetal growth and development. The rate and magnitude of these changes alter with gestational age.
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Understanding the regular physiological alterations that occur during pregnancy is essential for distinguishing between pregnant women with pregnancy-related complications and pregnant women who are healthy.
What Is Maternal Fetal Drug Transfer?
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The placenta is the connection between the mother and the fetus. The placenta transports nutrition to the fetus and waste products produced by metabolic processes in the fetus to the mother for excretion.
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Drugs given to pregnant women may affect the fetus as they pass through the placenta.
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A better understanding of the structure and functioning of the placenta is crucial for comprehending how drugs are passed from mother to fetus.
What Is the Structure and Function of the Placenta?
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The placenta is an important organ in which the fetus grows that is disc-shaped that connects the mother with the fetus. The chorionic villi are the placenta's most basic structure.
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The villi are vascular structures within the chorion (the outermost fetal membrane). The intervillous space is ample cavernous between villi containing maternal and fetal blood vessels.
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At Week eight (gestational age), the mother's uterine blood vessels reach the intervillous space, which is sufficiently large to accommodate 400 to 500 milliliters of blood.
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Through the placenta, gasses, nutrients, and drugs administered to the mother are transferred to the fetus. Generally, drugs injected into the mother can be transferred to the fetus and affect the fetus.
What Is the Effect of Local Anesthetics on the Fetus?
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Drugs given to the mother are passed on to the fetus through the placenta, though the amount of transfer varies. The effect of transferred drugs on the fetus can differ based on the drug type and the general conditions of the fetus.
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The most commonly utilized drugs in dental treatment are local anesthetics. Unfortunately, dental diseases are more prevalent in pregnant women. Knowledge of the effects of local anesthetics on the fetus is therefore critical for providing safe and efficient dental care to pregnant women.
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Moshira et al. investigated the toxicity of the local anesthetics Lidocaine and Etidocaine when administered to fetal and neonatal lambs. Because fetuses have a large distribution of blood vessels, the volume of drug distribution is high, which may explain the reduced sensitivity in fetuses to the toxic effects of drugs.
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The sensitivity of fetuses with asphyxia to neurologic and cardio-vascular toxicity of local anesthetics is increased. In addition, local anesthetic protein binding capacity is reduced in an asphyxiated fetus compared to a normal fetus, and Lidocaine becomes trapped due to tissue acidosis.
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While administering local anesthetic care should be taken especially in pregnant women, as fetuses are at significant risk of asphyxia or having poor general conditions because they are more likely to suffer side effects.
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The amount of local anesthetic transferred across the placenta determines the extent of the effects on a fetus.
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The dosage of local anesthetics given is based on the route of administration and the utilization of the vasoconstrictor, rate of metabolism of the anesthetic.
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Ester-type local anesthetics hydrolyzed in the plasma by esterase have a shorter duration of action than amide-types. Because ester types are quickly hydrolyzed in the mother's plasma, they have little effect on the fetus.
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Local anesthetic allergic reactions can endanger the mother and the fetus, and ester types are more likely to result in these anaphylactic reactions. However, the chances of amide-type local anesthetics causing allergic reactions are extremely low.
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Amide-type local anesthetics, widely used clinically, exert different effects depending on their type. The amount of amide-type drug delivered to a fetus is affected mainly by the extent of maternal protein binding.
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The free compounds that are readily available cross the placental barrier. Hence, the protein-binding capacity of the anesthetic decides the ratio of the maternal-to-fetal transmission of the drug. Among all the currently available anesthetic drugs, Bupivacaine has the lowest transmission ratio.
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In obstetrics, Bupivacaine is commonly used as a local anesthetic. Bupivacaine works by inhibiting cardiac conduction at toxic levels, resulting in cardiac arrest with a low chance of survival.
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As a result, a high concentration of Bupivacaine is not presently used in dental procedures to induce local anesthesia. Lidocaine is generally used in routine dental practice.
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Lidocaine's protein binding capacity is less than that of Bupivacaine. Because the free Lidocaine proportion is generally high, the amount of Lidocaine transferred from the mother to the fetus is also relatively high.
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Vasoconstrictors are added to Lidocaine to decrease absorption and toxicity and improve the analgesic effects.
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Epinephrine-induced vasoconstriction slows the absorption of local anesthetics by the mother, allowing Lidocaine absorption to take place slowly in the maternal systemic circulation while also enabling blood levels of Lidocaine to increase.
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The local anesthetic is slowly transferred to the fetus, increasing its margin of safety. Given that local anesthetics have minimal direct effects on the fetus at a submaximal level, Lidocaine may be considered reasonably harmless for pregnant women.
What Are the Potential Effects of a Maternally Administered Drug According to Gestational Age?
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During the First Trimester: The first trimester lasts until 13 weeks after the implantation of the fetus. During this time, the development of the most critical structures is complete, limbs form, and the fetus begins to move. Vital structures formed during this trimester continue to grow throughout the pregnancy, and the possibility of an organ abnormality developing after this period is relatively low. However, when a fetus is subjected to chemicals that can cause genetic variations in the process of cell growth and chromosome proliferation, the fetus may develop a congenital disability. In addition, because organogenesis is active during weeks Four to ten weeks (gestational age), fetal exposure to drugs may have teratogenic effects. Therefore, dental procedures could not be performed until the end of this phase.
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During the Second Trimester: In terms of gestational age, the second trimester extends from fourteen to twenty-seven weeks. The chance of drug teratogenicity is lower during this time than in others. Therefore, most dental professionals are cautious about performing dental procedures. Elective dental treatment, however, has been reported to be reasonably safe. However, the risk of lower blood pressure in the supine position increases after 20 weeks due to aortocaval compression. Aortocaval compression also reduces blood flow into the uterus, which can harm the fetus. These risks must be considered when conducting dental procedures on pregnant women during this period of pregnancy.
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During the Third Trimester: As the fetus grows during this phase, the uterus enlarges, causingaortocaval compression in the supine position is more highly probable in the third trimester. Symptoms such as low blood pressure and light-headedness that may occur when resting in the supine position can be relieved by placing a pillow on one side of the back to support the lateral position. Low-dose local anesthetic use may be possible for pregnant women in the third trimester, significantly reducing the expression of toxic effects of local anesthetics.
Conclusion:
When pregnant women are given local anesthetics during dental procedures, both the woman and the fetus are exposed to the drugs. As a result, when planning dental procedures to enhance the mother's oral health, the effects of local anesthetics on the mother and the fetus must be taken into account. Using local anesthetics in dental procedures for pregnant women seems to have a low impact on the women and their fetuses. However, because drug exposure in the first trimester has a significant risk of teratogenic effects, dental intervention is recommended only after the second trimester.
