Pregnancy causes many changes in the physiology of the female patient, deepening the challenges for the dental provider. These alterations are sometimes subtle, but can lead to disastrous complications if proper precautions are not taken. Physiologically, changes occur in the cardiovascular, hematologic, respiratory, gastrointestinal, and genitourinary systems. Cardiovascular changes during the second and third trimesters facilitate a decrease in blood pressure and cardiac output that can occur while the pregnant patient is in a supine position in the dental chair. Respiratory changes lead to a decrease in functional residual capacity, which, when combined with an increase in oxygen consumption by the gravid uterus, results in a significant depletion in the oxygen reserve of the pregnant patient. While medications are commonly used in dental and surgical practice during pregnancy, careful consideration must be given to their effect on maternal and fetal health. Local anesthetics freely cross the placental barrier, so the issue of fetal toxicity must be considered. This chapter also discusses whether nitrous oxide is safe to use in pregnancy, what antibiotics are best to treat dental infections in pregnant patients, and what recommendations are there for managing dental and postsurgical pain in pregnant patients. It is important for the reader to remember that all treatments during pregnancy are essentially rendered to two patients: the mother and the fetus. All treatment should be conducted only after consultation with the patient’s gynecologic specialist.
Introduction
Pregnancy causes many changes in the physiology of the female patient, deepening the challenges for the dental practitioner. These alterations are sometimes subtle, but can lead to disastrous complications if proper precautions are not taken. Physiologically, changes occur in the cardiovascular, hematologic, respiratory, gastrointestinal, and genitourinary systems (▶ Table 14.1).
Cardiovascular System
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Cardiac output (heart rate × stroke volume) increases 30 to 50% during pregnancy secondary to 20 to 30% increase in heart rate as well as 20 to 50% increase in stroke volume.
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Increased stroke volume is predominantly responsible for the early increase in cardiac output, possibly due to increased left ventricular mass and blood volume.
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During the second and third trimesters, a decrease in blood pressure and cardiac output can occur while the patient is in a supine position.
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This has been attributed to the decreased venous return to the heart from the compression of the inferior vena cava by the gravid uterus.
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Compression of the descending aorta can also occur, leading to decreased blood flow to the common iliac arteries.
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Hypotension, bradycardia, and syncope characterize supine hypotension syndrome.
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Not all patients become symptomatic in the supine position, but those who do may experience an initial increase in heart rate and blood pressure that soon decreases.
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While the supine pregnant patient may be asymptotic, a substantial decrease in uteroplacental perfusion can still occur.
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Placing the patient at 5 to 15% tilt on her left side can relieve supine hypotension.
Respiratory System
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An estimated 30% of all gravid patients experience symptoms of severe rhinitis.
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These changes have been attributed to the direct effects of estrogen and the indirect effects of increased blood volumes.
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Rhinitis during pregnancy appears at the beginning of the second trimester and increases in severity until delivery, then it often resolves within 48 hours.
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Mucosa in the upper airways may also become generally more edematous and friable.
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Hyperventilation begins in the first trimester and may increase by up to 42% in late pregnancy.
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This is due in part to lower arterial carbon dioxide tension and increased renal bicarbonate excretion.
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There is also a postural effect, as well as the respiratory stimulant effects of progesterone.
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The supine position is associated with an abnormal alveolar-arterial oxygen tension gradient that significantly improves when women shift back to the sitting position.
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Approximately 50% of pregnant women complain of dyspnea by week 19 of gestation, which increases to 75% by 31 weeks.
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The dyspnea cannot be correlated with any single parameter of respiratory function; therefore, women who complain of dyspnea may only be more aware of the increased ventilation during pregnancy.
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Anatomically, the diaphragm is displaced superiorly by approximately 4 cm, which is compensated for by an increase in the transverse diameter of the thorax and the chest circumference, resulting in a 40% increase in vital capacity.
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The diaphragmatic displacement leads to 15 to 20% reduction in functional residual capacity.
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There also is a baseline 15% increase in oxygen consumption by the gravid uterus.
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These two factors result in a significant depletion in the oxygen reserve of the gravid patient.
Anesthetic and Pharmacologic Considerations
Although medications are commonly used in dental and surgical practice during pregnancy, careful consideration must be given to their effect on maternal and fetal health (▶ Table 14.2).
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