Disclosure
Approximately 1 million women of childbearing age in the United States have seizure disorders. Of these women, approximately 20,000 give birth each year. Concerns during these pregnancies include the risk of fetal malformation, miscarriage, perinatal death, and increased seizure frequency. Women with epilepsy appear to have a greater baseline risk of fetal malformations, which is further increased with the use of antiepileptic drugs (AEDs). During pregnancy, the volume of distribution and hepatic metabolism of AEDs are increased. This, along with decreased compliance with AEDs because of concerns about effects on the fetus, leads to an increase in seizure frequency, which is observed in as many as 17-33% of pregnancies. When treating these women during pregnancy, the risks of increased seizure frequency versus the risks of AED use must be weighed carefully. For excellent patient education resources, visit eMedicine's Pregnancy and Reproduction Center. Also, see eMedicine's patient education article Miscarriage.
The earliest reports of congenital malformations associated with AEDs occurred in the 1960s. Since then, unique malformations and syndromes have been ascribed to phenytoin, phenobarbital, primidone, valproate, carbamazepine, and trimethadione. However, similarities exist among most of the congenital abnormalities caused by the AEDs (see Table). Older evidence has indicated that women with epilepsy have an increased risk of fetal malformations, even without AED use. However, one recent systematic review of the topic found no statistically different rate of major fetal malformations among epileptic patients on no medications compared with normal controls. While some studies suggest that monotherapy does not increase that baseline risk over patients not on AEDs, most of the literature suggests that first-trimester use of even a single AED is associated with a 2- to 5-fold increase in major malformations. Furthermore, multiple studies present evidence indicating an increase in fetal malformations with AED polytherapy. Specific increases in congenital abnormalities observed in infants born to mothers with epilepsy include a 4-fold increase in cleft lip and palate and a 3- to 4-fold increase in cardiac anomalies. An increase in the rate of neural tube defects is also observed in the offspring of patients with epilepsy who are using carbamazepine or valproic acid. Long-term studies on neurodevelopment show higher rates of abnormal EEG findings, higher rates of developmentally delayed children, and lower intelligence quotient (IQ) scores. Fetal Anomalies Associated With AEDs
Phenytoin Fetal hydantoin syndrome was first described in 1973 by Loughnan et al. It consists of an array of anomalies, including craniofacial anomalies, distal digital hypoplasia, epicanthal folds, hypertelorism, low-set ears, and developmental delay. The early descriptions of this syndrome were noted in 12 infants, 11 of whom had been exposed to other AEDs, notably barbiturates. Of infants born to women who used phenytoin during pregnancy, 10-30% are reported to exhibit some of the syndromic findings, most commonly distal digital hypoplasia. However, few infants exposed to monotherapy have the entire constellation of findings. Of note, in a recent long-term neurodevelopmental study, 16 patients whose mothers received phenytoin monotherapy during pregnancy demonstrated slightly delayed locomotor development compared with children whose mothers took carbamazepine and with normal controls. Phenobarbital and primidone Infants exposed to phenobarbital have been reported to have many of the findings observed in infants with fetal hydantoin syndrome and fetal alcohol syndrome. Furthermore, many of the infants initially described as having fetal hydantoin syndrome were also exposed to phenobarbital. A recent drug registry reported 5 (6.5%) of 77 patients who had received phenobarbital monotherapy had fetuses with major malformations, compared with a background rate of 1.6%. Primidone is metabolized to phenobarbital; thus, many of the effects on the fetus are similar. In 1979, Rudd and Freedom reported a specific description of a possible distinct primidone embryopathy, which includes a hirsute forehead, thick nasal roots, a long philtrum, and anteverted nostrils. However, many of these findings were similar to those found in association with phenobarbital and phenytoin exposure. Valproic acid A syndrome of specific craniofacial abnormalities and long, thin digits with hyperconvex nails has been described in infants exposed to valproic acid during pregnancy. Furthermore, in 1982, an association between valproic acid and neural tube defects was noted at a rate of 1-2%, 20 times greater than the baseline population. In recent studies comparing valproic acid with carbamazepine, valproic acid appears to be associated with a higher risk for major congenital malformations as well as developmental delay and decreased verbal intelligence. Further, one study demonstrated a dose-response effect, with patients taking the highest doses of valproic acid at greatest risk. Carbamazepine In 1989, a syndrome that included craniofacial abnormalities and hypoplastic nails was described in infants exposed to carbamazepine monotherapy in utero. In a cohort study in 1996, 6 of 47 infants demonstrated this syndrome. These infants also had lower IQ scores than controls. However, a recent analysis of 86 patients on carbamazepine monotherapy showed no difference in IQ scores compared with normal controls. Carbamazepine is also associated with an increased risk of neural tube defects in as many as 0.5-1% of births (ie, 10 times the baseline risk). Carbamazepine is also associated with a risk of cardiac anomalies; thus, for patients taking this drug, a fetal echocardiogram is recommended at 20-22 weeks' gestation. Trimethadione In 1975, a cluster of findings, including epicanthal folds, low-set ears, microcephaly, short stature, and irregular teeth, was ascribed to trimethadione. A review of 57 pregnancies published in 1977 revealed either malformations or fetal loss 87% of the time. Currently, trimethadione is rarely used in the treatment of epilepsy and certainly should be discontinued during pregnancy. Gabapentin, lamotrigine, felbamate, topiramate, and oxcarbazepine These newer anticonvulsants have not been studied extensively in pregnancy. Several studies of in utero exposure reported either case reports of anomalies or no effects on the fetus. None of these studies revealed a rate of congenital malformations greater than that for a woman with epilepsy who is not taking AEDs. The new anticonvulsants generally have a better pharmokinetic profile and are not metabolized to known teratogens. All of these anticonvulsants are considered US Food and Drug Administration pregnancy category C. Of note, they are still known to both cross the placenta and into breast milk.
The mechanisms of teratogenicity of the AEDs have not been fully characterized. Phenobarbital, primidone, and phenytoin act as folate antagonists. Certainly, a folate deficiency appears to lead to an increase in congenital malformations, particularly neural tube defects; thus, folate administration prior to conception has been recommended for prophylaxis. Because AEDs all have a similar central mechanism to control seizures, a common pathway that is disrupted during embryogenesis may lead to the similarities in the syndromes described, and this may be why an additive effect is observed with polytherapy. Recent studies in teratogenesis, particularly fetal hydantoin syndrome, point to a genetic predilection for the generation of epoxides. These anomalies have been observed at an increased rate in children whose enzyme activity of epoxide hydrolase is one third less than the reference range. Anomalies have also been observed in children with low epoxide hydrolase activity who were exposed to carbamazepine. Regarding the cognitive and neurodevelopmental differences seen, one interesting study demonstrated that among rats treated with AEDs to achieve therapeutic levels, apoptosis of neural tissue was noted. This is consistent with smaller brains demonstrated in animal studies and may be a causal mechanism in the lower IQs and developmental delay seen in a minority of these patients. |
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Because exposure to multiple AEDs seems to be more teratogenic than monotherapy, patients are advised to switch to a single AED prior to conception and taper to the lowest possible dose (see Preconceptual management of women with epilepsy). Patients who have not had a seizure for 2-5 years may wish to attempt complete withdrawal from AEDs prior to conception. Because evidence indicates that high peak plasma levels of valproic acid may be more teratogenic, this drug should be dosed at 3-4 times per day rather than the standard twice-per-day dosing. However, patients with epilepsy should be counseled that they are still at a greater risk (ie, 4-6% vs 2-3%) for fetal anomalies than the baseline population. Because folate has been shown to decrease neural tube defects in patients without epilepsy, patients, particularly those using either valproic acid or carbamazepine, should be advised to take supplemental folate prior to conception. Because of the increased risk of anomalies, a level II fetal survey should be performed at 19-20 weeks' gestation, with careful attention to the face, central nervous system, and heart (see Management of women with epilepsy during pregnancy). Because of the increased risk of neural tube defects, a maternal serum alpha-fetoprotein (MSAFP) screening test should be offered. Whether to perform an amniocentesis routinely for alpha-fetoprotein and acetylcholinesterase is controversial. Many authors recommend it in the setting of a family history of neural tube defects or with the use of valproic acid or carbamazepine because the sensitivity of amniocentesis is higher than either MSAFP screening tests or ultrasound for detecting neural tube defects. Reports of increased risk of spontaneous hemorrhage in newborns suggest that the inhibition of vitamin K–dependent clotting factors (ie, II, VII, IX, X) secondary to increased vitamin K metabolism and the inhibition of placental transport of vitamin K results from AED use. Historically, most patients on AEDs received oral vitamin K supplementation at the end of pregnancy. However, a recent study of 204 neonates born to mothers taking AEDs who did not received vitamin K supplementation showed no evidence of coagulopathy. Upon delivery, clotting studies can be performed on the cord blood, and vitamin K can be administered to the infant. If the cord blood is deficient in clotting factors, fresh frozen plasma may be required to protect the newborn. Preconceptual management of women with epilepsy
Management of women with epilepsy during pregnancy
Generalized tonic-clonic seizures during pregnancy can lead to increased maternal trauma. If the maternal trauma involves the abdomen, a theoretical risk of abruption possibly leading to fetal hypoxia or death exists. Furthermore, the risk of maternal aspiration can lead to maternal hypoxia, which can also lead to fetal hypoxia. Evidence indicates seizure frequency increases during 17-33% of pregnancies. Several possible etiologies have been proposed for this occurrence. Increased renal and hepatic metabolism of the AEDs, increased volume of distribution, and changes in serum-binding proteins all impact circulating levels of AEDs. The increased stress, hormonal changes, and decreased sleep during pregnancy likely lower the seizure threshold and have been shown to increase seizure frequency in patients who are not pregnant. Finally, many women may have decreased compliance with taking AEDs because of concerns regarding the effects on their fetuses. Increased levels of circulating estrogen during pregnancy increase the function of the P-450 enzymes, which leads to more rapid hepatic metabolism of the AEDs. Also, renal function increases during pregnancy, with a 50% rise in creatinine clearance, which impacts the metabolism of carbamazepine, primidone, and benzodiazepines. The increase in total blood volume and a concomitant rise in the volume of distribution also lead to decreased levels of circulating AEDs. In contrast, the decrease in albumin and circulating plasma proteins likely increases the free component of the AEDs in serum. The increased levels of both estrogen and progesterone may have a direct impact on seizure activity during pregnancy. Estrogen has been shown to be epileptogenic, decreasing the seizure threshold. Thus, the rising estrogen levels in pregnancy, which peak in the third trimester, may have some impact on the observed increase in seizure frequency. Conversely, progesterone seems to have an antiepileptic effect, and women with seizure disorders have been observed to have fewer seizures during the luteal phase of the menstrual cycle. Rarely, some patients experience their first seizures during pregnancy. This can be a result of true gestational epilepsy, a rare syndrome of seizures occurring only during pregnancy. Patients with this syndrome have a variable presentation with single or multiple seizures in one or more of their pregnancies. It can also be a manifestation of epilepsy (see Women's Health and Epilepsy and Seizures and Epilepsy: Overview and Classification) that may extend beyond the pregnancy. The workup of these patients should involve a neurologic examination, consultation with a neurologist, CBC count, chemistry panel (particularly for electrolytes), head MRI versus CT scan, and EEG. The differential diagnosis should include eclampsia (see Eclampsia, Preeclampsia and Eclampsia, and Preeclampsia (Toxemia of Pregnancy)) and any possible etiology considered in the nonpregnant patient, including stroke, electrolyte abnormalities, tumor, trauma, drugs/withdrawal, and epilepsy. |
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Recent studies of seizure frequency show a smaller increase in seizure frequency than older studies, which suggests that the practice of closer monitoring of AED dosing and levels may have some impact on the number of seizures during pregnancy. A recent study showed that 38% of pregnant patients with epilepsy required changes in their AED dosing to achieve seizure control. Assuming that successful monotherapy with one of the AEDs has been achieved preconceptually, the same total and free levels of the AED that keep the patient from having seizures should be maintained (see Management of women with epilepsy during pregnancy). In most patients with epilepsy, total levels of AEDs are followed; however, because of the aforementioned physiologic changes of pregnancy, checking free levels in patients who are difficult to treat may be more useful. Most authors suggest that these AED levels should be monitored monthly during pregnancy, with adjustment of dosing based on these levels and the clinical manifestations of seizure frequency.
Treating a patient with epilepsy during labor and delivery should include preparation and close monitoring. All care providers, including obstetricians, neurologists, nurses, anesthesiologists, and pediatricians, should be informed during labor and delivery that the patient has epilepsy. AED levels should be checked upon admission (see Management of women with epilepsy upon labor and delivery). If the serum drug level is low, patients may be administered extra doses or may be switched over to intravenous benzodiazepines or phenytoin, although benzodiazepines can cause respiratory depression in both the mother and the newborn. Because trauma and hypoxia from a seizure can put both the mother and fetus at risk, treatment of seizures should be discussed a priori with the group of practitioners who are caring for the patient. Rarely, a patient has intractable seizures upon labor and delivery. When these last longer than 30 minutes with either (1) a continuous seizure or (2) a lack of full recovery between seizures, the patient is considered to be in status epilepticus. Assuming that preeclampsia and eclampsia have been excluded, the protocol for managing status epilepticus is similar to the management of any seizure, ie, using benzodiazepines, phenytoin, and, rarely, phenobarbital (see Management of a pregnant patient in status epilepticus). During this situation, the fetus must be monitored. In the setting of nonreassuring fetal testing results, establish an airway and attempt intrauterine resuscitation. If the seizure is not treated easily and the fetal testing results continue to be nonreassuring for longer than 10 minutes, a neuromuscular blocking agent can be administered and emergent cesarean delivery can be performed. Management of women with epilepsy upon labor and delivery
Management of a pregnant patient in status epilepticus
Pregnancies in patients with seizure disorders can be complicated by a variety of maternal and fetal issues. Patients can experience higher rates of seizures because of the lower serum plasma levels of their AEDs. The fetus is likely to be at increased risk for congenital abnormalities, most notably facial clefts, cardiac anomalies, and neural tube defects. Long-term outcomes show that children of patients with seizure disorders may have lower IQs and higher rates of developmental delay. Syndromes related to several of the AEDs, and to specific abnormalities observed in patients with seizure disorders, are not known to affect rates of chromosomal abnormalities. Women with epilepsy should be treated during pregnancy by a team of providers, including a perinatologist and a neurologist, that can focus on balancing the risks of seizures versus the administration of AEDs. Preconceptual management with tapering to AED monotherapy and folate supplementation are recommended. During pregnancy, AED levels should be monitored closely, and the fetus should be carefully screened for anomalies with serum testing, ultrasound, and, possibly, amniocentesis. Vitamin K supplementation for the patient and then for the newborn at the end of the pregnancy is controversial; the risks and benefits of this aspect of management should be discussed by the entire team of providers caring for the patient. With careful treatment of these patients, more than 90% have an entirely uncomplicated pregnancy.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
){kind=small}
