Bradley A. Shessel, DMD, resident in the department of oral and maxillofacial Surgery at Nova Southeastern University; Jason E. Portnof, DMD, M.D., associate professor and director of pediatric maxillofacial surgery at Nova Southeastern University; Steven I. Kaltman, DMD, M.D., professor and chair of the department of oral and maxillofacial surgery at Nova Southeastern University; Romy Nitsch, M.D., assistant professor of obstetrics and gynecology at Queen’s University in Kingston, Ontario
The purpose of this review article is to assist the practicing clinician by categorizing and packaging useful clinical information into a format that will assist with the treatment of pregnant patients. Our goal is to offer the scientific foundations that lead to current practice guidelines, specifically those that are of particular relevance to today’s dental professional.
Pregnancy causes an array of complex physiologic changes in the female patient that must be appreciated by the dental health professional. These varied changes occur across multiple organ systems and significantly affect the patient’s cardiovascular/hemodynamic, hematologic, respiratory, gastrointestinal, genitourinary/renal and immune systems.1
Pregnancy is divided into three trimesters based on a 42-week gestation, or three months (14 weeks) for each trimester. Since the standard of care for dental maintenance and recall is regular, six-month comprehensive oral evaluations, every pregnant patient is expected to seek dental treatment at some point during pregnancy.
Dental care has been proven to not only be safe and effective during pregnancy, but also necessary to promote sound oral health. It is imperative that dental treatment be coordinated among obstetric and oral health care providers.
While some may recommend that all treatment be completed only after consultation with the patient’s physician, this is not necessary for most dental procedures.2 The following items, however, should be addressed by obtaining a medical consultation:
- Treatment of any pre-existing past medical conditions (aside from pregnancy)
- Clarification of all medications being provided to the patient during pregnancy
- Elucidation of medical complications that may be the result of pregnancy
- Any special treatment recommendations that may improve individualized care for the pregnant patient
Pregnancy by itself is not a reason to defer routine dental care or necessary dental treatment. However, prudence may dictate that elective treatment is deferred until after delivery. It is important to remember that there are actually two patients to be considered, and all clinical decisions should be made to minimize risks to both the mother and fetus.
Common physiologic changes
Physiologic changes occur during pregnancy and are known to affect a wide array of organ systems. Most commonly, cardiovascular, hematologic and respiratory changes can be expected. However, pregnancy exacts a systemic toll and, in actuality, all organ systems are affected to some degree. In this review, we will attempt to highlight the concerns that may be considered most clinically relevant to the dental health provider.
Cardiac output increases during the late second trimester and can be associated with a systolic heart murmur which may be heard in up to 90 percent of pregnant patients.3 Of particular importance is a phenomenon which may be seen in the second and third trimesters known as supine hypotension syndrome or SHS.4
SHS is caused by a decrease in blood pressure and heart rate when the patient is in the supine position. This is thought to be caused by compression of the inferior vena cava or IVC by the gravid uterus, which results in up to 14 percent decrease in cardiac output.5 Clinical manifestations of SHS may include a transient initial increase in heart rate and blood pressure that is followed by hypotension, bradycardia and syncopy.5
It is important to note that even though the aforementioned symptoms may be absent, a significant decrease in uteroplacental perfusion pressure may still be present.5 If SHS is expected, it can be managed by placing the patient in a 5-15 percent tilt on her left side to relieve pressure on the IVC.6
Hematologic changes are varied and significant. Intravascular blood volume increases by 40 percent by the end of pregnancy due to increased fluid retention; however, blood cell mass remains relatively unchanged.
The result of this hemodilution is a physiologic anemia with the average hematocrit ranging from 30-35 percent.2 Additionally, iron deficiency and hypercoagubility, due to the increased production of clotting factors, may be present.3
Pregnant women are, in fact, at a five times greater risk of thromboembolism as compared to non-pregnant women.5
Pregnant patients experience an increase in leukocyte count of 5,000 to 10,000 cells. This is secondary to an increased circulation of catecholamines and cortisol, which causes a demargination of leukocytes from the endothelial lining of the vasculature.7
The respiratory system experiences several changes that must be considered when treating the pregnant patient. Hyperventilation begins during the first trimester and persists throughout pregnancy; as such, pregnant patients should be considered to have a baseline respiratory alkylosis.
Capillary enlargement leads to increased upper airway edema and, therefore, an increased risk of supraglottic obstruction. The gravid uterus causes a superior displacement of the diaphragm of up to 4 cm, which leads to a decrease of 15-20 percent in functional residual capacity or FRC.2,8
Additionally, the pregnant patient experiences an increased oxygen consumption of 15-20 percent.2,5 Resultantly, pregnant patients experience a significantly reduced oxygen reserve.
As previously mentioned, there are several other organ systems that are significantly affected in the pregnant patient. A full listing of this complex physiology has not been provided in this paper as it goes beyond the scope of this review.
Clinicians who may be interested in additional reading are directed to the references section for further information.
Treatment Considerations by Trimester
The initial determination prior to treatment of the pregnant patient focuses on the patient’s total weeks of gestation or term. This calculation is based on the patient’s estimated date of delivery. The estimated date of delivery is calculated by counting 40 weeks from the first day of the last menstrual period.
Emergency dental procedures can be performed during any trimester when a delay in necessary treatment could result in significant risk to the mother and an indirect risk to the fetus.5,9 Special precautions may need to be taken during these instances.
First day of the last menstrual period until 13 weeks and six days gestation.
Diagnosis, oral prophylaxis and treatment, including necessary dental X-rays, can be safely performed during the first trimester in order to diagnose disease processes that require immediate treatment.5 Important issues to consider are:
- Fetal organogenesis occurs during the first 12 weeks of gestation. The conceptus is called an embryo until the ninth week, when it becomes a fetus.
- It is during the embryonic period when the risk of teratogenicity is highest.
- Dental care during early pregnancy has not been reported to increase the rate of malformations or pregnancy loss.
- Morning sickness usually resolves after the first trimester, so women may be more comfortable receiving non-emergent dental care at that time.
14-20 weeks gestation.
It is generally accepted that the safest time to perform elective dental procedures is in the early second trimester.1,2,3,5,9,10
28 weeks gestation until birth.
In the third trimester, when the pregnant patient is supine, the gravid uterus may obstruct the IVC and pelvic veins, impeding venous return to the heart and causing SHS. As previously mentioned, the common clinical manifestations of SHS include lightheadedness, hypotension, tachycardia and syncope.
Proper patient positioning is therefore very important. Left uterine displacement is achieved by placing a small pillow under the patient’s right hip and lifting the right hip and buttock 15 degrees.
Alternatively, the patient can lean on her left side, thereby reducing the pressure on the vena cava.
The Food and Drug Administration has classified the safety profile of medications for use during pregnancy. The following charts are helpful guides illustrating this classification scheme (Table 1 Table 2).
Clinicians should be mindful that when treating pregnant patients, all medications prescribed should be for the lowest effective dose and for the shortest duration possible.
The use of local anesthetics is necessary and acceptable during pregnancy.12 The clinician should be aware that local anesthetic agents may exhibit a more rapid onset and longer duration of action during pregnancy. Local anesthetics freely cross the placenta, and the potential for fetal toxicity is also a concern. (Table 2)
The use of vasoconstrictors with local anesthetics during pregnancy is controversial. Judicious use of a vasoconstrictor, however, is permissible.
Obtaining profound local anesthesia and thus, preventing extensive endogenous catecholamine release is the objective. A major concern with the use of local anesthetics containing epinephrine involves the inadvertent intravascular injection.
Accidental intravascular injection of epinephrine can cause uterine artery vasoconstriction and decreased uterine blood flow.13 Proper aspiration techniques and limitation of alpha-adrenergic agents (such as epinephrine) are advised to avoid this complication. 13
Clinicians may consider using carpules with 1:200,000 concentrations of epinephrine as an alternative.
Acetaminophen is the analgesic of choice in the pregnant patient. NSAIDs such as Ibuprofen and naproxen must be administered with particular care. These drugs are both classified as Category B for the first and second trimesters, but are considered Category D in the third trimester. This is because they have been shown to increase the risk of closure of the fetal ductus arteriosus; they have been shown to cause fetal renal damage and inhibit clotting.13
Codeine should be considered as a first choice narcotic when indicated, as it has been proven safe by evidenced-based studies.14 While all narcotics should be used judiciously, it is reasonable to use adequate analgesia to control maternal pain symptoms.
Benzodiazepines, such as midazolam and diazepam have been implicated as a possible cause of craniofacial defects, such as cleft lip and palate; however, no definitive causal link has been established.15
Odontogenic and other maxillofacial infections must be treated with particular alacrity in the pregnant patient. This often necessitates the administration of antibiotics.
Fortunately, most of the commonly used antibiotics in dentistry are classified as Category B drugs. These include: penicillin, amoxicillin, cephalexin, clindamycin and azithromycin.11
Importantly, antibiotics such as sulfamethoxazole/trimethoprim and ciprofloxacin are classified as Category C, and their use should be avoided if possible.11 Tetracycline and its derivatives are Category D, and their use is contraindicated throughout pregnancy.11
This is because they have the capacity to bind to hydroxyapatite within the developing tooth bud, thus impairing enamel formation and causing tooth discoloration.16 Furthermore, these drugs have been shown to effect bone formation.16
Finally, it bears noting that due to increased maternal blood volume, often times conventional doses of antibiotics may prove ineffective in pregnant patients.17
Infections must be monitored closely and those that show poor response should be referred to an oral and maxillofacial surgeon for inpatient hospital management when applicable.
The use of nitrous oxide or N2O during the treatment of pregnant patients remains the subject of great controversy.
Most providers agree that N2O should be used only when local anesthetics are inadequate and after consultation with the patient’s prenatal care provider. One important consideration for pregnant patients is to avoid hypoxia, and as such, N2O should be used judiciously. If used, it is not recommended to exceed a 50 percent mixture of N2O to oxygen.18
Anecdotal surveys of several dental practitioners have suggested that long-term exposure to N2O may be associated with spontaneous abortion and birth defects, but there is a lack of concrete evidence to validate these assertions.18
It is known, however that N2O affects vitamin B-12 metabolism, which in turn inactivates methionine synthase, an enzyme which is necessary for the production of DNA.18 Therefore, it is recommended that N2O be avoided during the first trimester when organogenesis occurs.18
Since the 1960s, there has been a lot of concern regarding the risk not only to patients, but also to health care workers who are subjected to chronic exposure of N2O. However, it cannot be over-emphasized that a definitive relationship between N2O exposure and reproductive sequelae has never been established.
In spite of this, great care is taken to reduce chronic N2O exposure in the medical setting.
In 1977, the National Institute for Occupational Safety and Health researched the efficacy of scavenger systems and chose 50 ppm to be the maximum exposure limit for personnel in a dental setting.19 This is measured most easily by time-weighted average or TWA dosimetry, which is a badge that may be worn much like radiation dosimeter and analyzed by an infrared spectrophotometer.
However, in 1995, a comprehensive literature review conducted at University of Colorado regarding biohazards associated with N2O use concluded that there was no scientific basis for these previously established levels. As a result, the American Dental Association’s Council on Scientific Affairs and Council on Dental Practice issued the formal position statement that a maximum N2O exposure limit in parts per million has not been determined.18
At present, no direct evidence exists of any causal relationship between chronic low-level exposure to N2O and potential biologic effects. Regardless, use of evacuation scavenger systems remains the standard of care, and every attempt should be made to reduce the level of trace N2O to exposed health care personnel. The recommended evacuation flow rate has been established by NIOSH as optimal at 45 L/min (Table 3).
General anesthetic considerations
Pregnant patients must be considered to have a “full stomach” and have an increased risk for aspiration. Physical changes during pregnancy include an increased size of the uterus, which causes a mechanical superior displacement of the stomach and increases intragastric pressure.
These patients also are prone to increased gastric reflux, delayed gastric motility and reduced competency of the gastroesophageal sphincter. The decreased lower esophageal sphincter tone may be due to direct hormonal effects of progesterone.
Administration of H2 blockers and metoclopramide should be considered in these patients. If a general anesthetic is to be used, it is preferable for the patient to have an empty stomach for at least six hours.
Dental radiographs are both safe and necessary for the treatment of pregnant patients. None of the conventionally employed radiographic modalities will generate a significant dose of ionizing radiation that may threaten the well-being of the developing embryo and fetus.
Regardless, collimated beams, high-speed film (or digital systems), a lead apron and a thyroid collar are protective measures that should always be used.
Certainly, avoiding radiation exposure throughout the first trimester is paramount, and accordingly, this should be limited to only emergent situations. However, it has been well-documented that there has been no increase in reported congenital anomalies or intrauterine growth retardation for radiation exposure less than 5-10cGy.20,21
Practitioners should feel confident in knowing that a full-mouth series of dental radiographs results in only
8 ×10–4 cGy, while bitewing or orthopantomagram (panoramic) radiographs generate about one-third this amount.20
At present, the use of cone beam computerized tomography (CBCT) scanners has become an ever-increasing part of dentistry. CBCT scans provide a useful modality for evaluating dental implant treatment planning, dentofacial anomalies, craniofacial pathology and temporomandibular joint disorders.22
Therefore, CBCT scans may likely be considered during the course of treating pregnant patients. It must be noted that there are two major differences that distinguish CBCT scanners from helical or “medical grade” CT scanners.28 The first is that CBCT machines use a low-energy fixed anode tube to generate the flow of electrons, and secondly, CBCT machines only rotate around the patient one time as they capture data.22
The net result is that the patient is exposed to approximately 20 percent of the ionizing radiation dose as that of a helical CT scan.22 This is approximately equivalent to the radiation exposure from a full-mouth series of conventional radiographs.22
Obviously, the use of CBCT scans should be exercised judiciously and certainly lead aprons and thyroid collars should again be used at all times. If CBCT is deemed to be the necessary imaging modality, then the best decision is to limit the field of capture as much as possible to only the necessary anatomical structure in question.
The fundamental principle that should be maintained at all times is that the patient should be exposed to the lowest dose imaging modality possible, while still achieving the necessary diagnostic data.
Treatment of the postpartum breast-feeding patient
The American Academy of Pediatrics has formally stated its position that breast-feeding is the optimum nutritional source for the newborn infant in the first six months of life.23,24 Not surprisingly, a high percentage of postpartum women breast-feed throughout the first year.
In fact, in 2010 the Centers for Disease Control and Prevention released data on breast-feeding in the US. They report that from 2000-2008, the percentage of breast-feeding in the early postpartum period was 81.9 percent; 60.06 percent at six months; and even at 12 months after delivery, it still remained at 34.1 percent.25
Therefore, it is reasonable for the dental health practitioner to be concerned with any medications they provide to a breast-feeding patient and what sequelae may exist.
Several studies have examined the transmission of medications into milk in the bovine model.26 It is important to be aware that there is a paucity of data regarding human breast milk, primarily because radioactive isotopes are necessary for data collection.25 One problem with attempting to extrapolate information from the bovine model is that there is a difference in the pH between human milk and breast milk.25 So, while a direct correlate is not possible, the information available can be applied in a useful manner.
The general rule is that for most drugs, the infant is exposed to a considerably higher dose in utero than during lactation.25 Therefore, there is a much safer therapeutic index for medications that are used during lactation.
However, lactating patients should consider the “pump and discard” model. This is based on the fact that it takes the human body four half-lives of a drug to eliminate 90 percent of a drug. Prior to the application of a drug (especially a short-acting medication), the patient can be counseled to pump and store an appropriate amount of breast milk to last the duration of four half-lives of the drug.
Then after administration of the drug, she can pump and discard all breast milk for the corresponding time frame.25
The dental health practitioner should feel comfortable in knowing that the treatment of pregnant patients is not only permitted, but actually is necessary in order to promote sound oral health. The recommendations compiled within this review highlight the major treatment considerations that one may reasonably encounter over the course of routine practice.
The purpose of this article is not to create treatment algorithms, but rather to suggest that the treatment administered must be individualized to each patient.
However, if the principles and guidelines set forth here are applied in good judgment, then the treatment of this patient cohort can be administered in a both safe and effective manner.
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Dr. Shessel is a resident at the Department of Oral and Maxillofacial Surgery at Nova Southeastern University in Fort Lauderdale.
Dr. Portnof is an Associate Professor and Director of Pediatric Maxillofacial Surgery and Craniomaxillofacial Surgery at Nova Southeastern University.
Dr. Kaltman is Professor and Chairman of the Department of Oral and Maxillofacial Surgery at Nova Southeastern University.
Dr. Nitsch is an Assistant Professor of Obstetrics and Gynecology at Queen’s University, Kingston in Ontario.