Q&A 92.4
Is it safe to take herbal medicines during pregnancy?
Prepared by UK Medicines Information (UKMi) pharmacists for NHS healthcare professionals
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Date prepared:7th July2014
Background
A recent observational cohort study in South West England found that 26.7% (n=3774) of women had used a complementary or alternative medicine at least once during pregnancy; the use rising from 6% (n=824) in the first trimester to 12.4% (n=1639) in the second and to 26.3% (n=3269) in the third (1).Only 7.6% (n=1073) of women did not take any medicinal product (conventional or complementary) throughout the whole of their pregnancy. The most common herbal products were chamomile, peppermint, raspberry leaf and rosehip. Use of complementary medicines increased with age of the mother, with older mothers more likely to have used a complementary medicine than younger mothers (43.5% aged over 35 years and 15.2% aged 24 years or under) (1). Another United Kingdom (UK)-based study reported 57.8% (n=334) of women used herbal remedies during pregnancy, with a mean of 1.2 remedies (range 0-10) per woman. The most commonly used remedies were ginger, cranberry and raspberry leaf (2). Of some concern is that 76% of the pregnant women reported not informing their doctor or midwife that they were using herbal medicines, and that family or friends were the most frequently cited source of information about herbal remedies during pregnancy (2).
One recent survey involving 600 postpartum women in Norway found that 39.7% had used herbal medicines during pregnancy with an average of 1.6 products per woman. Echinacea, iron-rich herbs, ginger, chamomile and cranberry were the most commonly used herbal medicines (3).
Evening primrose oil, ginseng, green tea, flax andvalerian are also reportedly commonly used by women during pregnancy (4-6).
Herbal medicines are often mistakenly viewed as natural and safe alternatives to conventional medicines. Unfortunately, some plants have toxic constituents and many have constituents with pharmacological activity, such as stimulation of uterine muscle, which could render them unsuitable during pregnancy (7). Contamination with substances such as pesticides, conventional medicines or heavy metals cannot be ruled out. There is a published case report of a preterm infant found to have elevated blood lead levels as a result of the long-term ingestion of lead-contaminated herbal medicines by the mother (8). Lead poisoning has been reported in association with the use of Ayurvedic medicinesby pregnant women (9). These productsmay contain herbs only, or in some cases are combined with metals, minerals or other materials (10).
Preparations often differ with regard to the concentration and origin of their constituent herbs (11). Furthermore, many modern herbal preparations are available as highly concentrated extracts, the effects of which could differ substantially from those of more traditional preparations such as teas made from the leaves of herbs. Therefore the assumption should not be made that a preparation will be safe merely because its main herbal ingredient has been used during pregnancy for many years without apparent ill effect (11). As with conventional drugs, the route of administration (e.g. oral, rectal or injectable) should be considered when determining the safety of an herbal medicine. Finally, any assessment of risk should take into account potential interactions between the herbal preparation(s) and any conventional medicine(s) a women is taking, as well as her past obstetric history and general health.
Answer
Few scientific studies have looked at the effects of herbal medicines in pregnant women and literature reporting the outcome of pregnancies during which herbal medicines were used is limited. Because of the scarcity of relevant safety information, use of herbal medicines during pregnancy cannot be recommended. Despite this, it is clear that many pregnant women use herbal preparations, particularly for pregnancy-related symptoms. The following information covers the herbal medicines most likely to be in common usage by pregnant women.
Blue Cohosh
Blue cohosh has traditionally been used to induce labour (12). There are three case reports in the literature of potential adverse effects in the neonate following maternal exposure to blue cohosh around the time of delivery. In the first case stroke was reported in a neonate whose mother had taken a tea made of blue cohosh (13). The tea was found to contain a metabolite of cocaine and the authors noted that maternal use of cocaine is a cause of perinatal stroke. It is unclear if the cocaine metabolite was also a metabolite of blue cohosh or a contaminant in the tea. No follow up details are provided for this case. In the second case report a neonate experienced a myocardial infarction associated with congestive heart failure and shock (14). The mother had taken three times the recommended daily amount of blue cohosh tablets for three weeks to induce labour. The authors state that other causes of myocardial infarction were ruled out. The infant went on to recover though some cardiac symptoms persisted at 2 years of age (14). In the third case severe multi-organ hypoxic injury was reported in a neonate whose mother had taken a blue and back cohosh herbal mixture (15). At three months there was lower limb spasticity and the infant required nasogastric tube feeding (15). In vitro evidence suggests that blue cohosh may have teratogenic, embryotoxic and oxytoxic effects (16). There have been calls for tighter control of its use and for further investigations into its safety (16).
Chamomile
Traditionally, chamomile is used as a mild sedative and to aid digestion (3), and has reportedly been used for the treatment of morning sickness (17). There are two types of chamomile – German and Roman. German chamomile is the type used most often as a medicinal herb. Extracts of German chamomile have been reported to increase the tone of uterine muscle (18). There is a documented case in which a 35-year-old woman received an enema made from German chamomile and experienced life-threatening anaphylaxis; her baby experienced severe asphyxia and died the following day (19,20).
Two cases of premature constriction of the foetal ductus arteriosus have been reported following the maternal consumption of chamomile herbal tea (21). The first patient reported drinking chamomile tea on a regular basis. A constricted ductus arteriosus and increased blood velocity across it was seen at 20 weeks’ gestation on foetal echocardiography, including Doppler velocity. The patient was advised to stop drinking the tea and re-assessed one week later, which revealed complete resolution of ductal constriction with no acceleration in blood flow velocity across the ductus arteriosus (21). The second case was referred for foetal cardiac assessment at 35 weeks’ gestation on suspicion of foetal tachycardia. Doppler imaging confirmed high diastolic flow velocities with a pattern consistent with ductal constriction. The patient confirmed intermittent consumption of chamomile tea during pregnancy, including about 48 hours before the scan (21). The authors have postulated that ductal constriction associated with the consumption of chamomile tea is likely to be produced by a similar pharmacological mechanism to that observed with non-steroidal anti-inflammatory drugs, due to its inhibitory effects on the cyclo-oxygenase and lipo-oxygenase pathways of arachidonic acid metabolism (21).
Roman chamomile is believed to be an abortifacient (22, 23).
Both types of chamomile should be avoided during pregnancy until further information is available (17).
Cranberry
Cranberry is used orally to prevent and treat urinary tract infections (24). Reliable scientific information on the use of cranberry during pregnancy is not available (24, 25). Cranberry at the doses normally found in foods are not known to cause problems in pregnancy, but medicinal doses of cranberry should be avoided by pregnant women (26).
Echinacea
Echinacea is commonly used orally to treat and prevent the common cold and other upper respiratory infections (27). Only one prospective study (28) has looked at pregnancy outcome after gestational exposure to echinacea. The study included 412 pregnant women who had contacted a teratogen information service to ask about the safety of echinacea for an upper respiratory tract illness. The study group comprised those who went on to take echinacea (n=206), whereas those who chose not to use it or used a non-teratogenic antibiotic instead formed the control group (n=206). In the study group, use of echinacea was generally for between five and seven days and 54% (n=112) of women used echinacea during the first trimester. The groups did not differ statistically significantly with regard to pregnancy outcome, delivery method, gestational age, birth weight or foetal distress. In the study group, 6 major and 6 minor malformations occurred and in the control group there were seven major and seven minor malformations. As the authors noted, limitations of the study included the small sample size and lack of standardisation of doses (tablets, capsules and tinctures in varying doses were used) (28). Further evidence of the safety of echinacea during pregnancy is required (29,30).
Evening Primrose Oil
Midwives reportedly use evening primrose oil to expedite cervical ripening, in an attempt to shorten labour and reduce the incidence of postdate pregnancies (31). One study compared outcomes in 54 women who took evening primrose oil orally from week 37 of pregnancy with those in 54 women who did not. No difference in the overall length of labour was found between groups. Further, it was concluded that women taking evening primrose oil might be more likely to experience prolonged rupture of membranes, oxytocin augmentation, arrest of descent and vacuum extraction (31).
One report was found of ecchymoses and petechiae on the trunk, extremities and face of a female baby, aged 17 hours. The infant had no other symptoms. In the week before delivery her mother had taken raspberry leaf tea and a total of thirteen 500mg capsules of evening primrose oil, vaginally and orally, in an attempt to improve labour. The authors suggested that the evening primrose oil had inhibited platelet function in the newborn infant. The platelet count was reported as normal in the infant and her symptoms resolved spontaneously by day 5 (32).
Flax
There is very little information on the effects of flax during human pregnancy, but it might have oestrogenic effects, which would be a cause for concern in a pregnant woman (33). One study found that flax use during the last two trimesters of pregnancy was associated with an increased risk of preterm birth (34).
Ginger (root)
Between 50 and 80% of women experience nausea during pregnancy (35). A Cochrane review on interventions for nausea and vomiting during pregnancy concluded that the use of ginger may be helpful to women, but the evidence of effectiveness was limited and inconsistent (35). The current National Institute for Health and Clinical Excellence (NICE) guidance on antenatal care highlighted that ginger appears to be an effective intervention in reducing nausea and vomiting symptoms in early pregnancy (36).
According to information produced by the UK Teratology Information Service, two cohort studies and several small clinical trials found no increase in the incidence of adverse pregnancy outcomes, including congenital malformations, when ginger was used during pregnancy. Despite this, since only small numbers of pregnant women have been exposed to ginger in studies, the risk of adverse effects cannot be completely ruled out (37).
Areview on the efficacy and safety of ginger for pregnancy-induced nausea and vomiting includedsix double-blind randomised controlled trials (RCTs) (n=675) and one prospective observational cohort study (38). Ginger doses in the trials ranged from 125mg ginger extract four times a day to 500mg three times a day. The prospective observational cohort study involved 187 women exposed to ginger during the first trimester of pregnancy and 187 women exposed to non-teratogenic drugs. Dosage and origin of the ginger were not documented. No statistically significant differences were noted between the two groups for live births, spontaneous abortions, still births, therapeutic abortions, birth weight or gestational age. Follow-up of four of the reviewed RCTs found ginger to have no significant adverse effects on pregnancy outcome. Adverse effects taken into account included antepartum haemorrhage, pre-eclampsia, preterm birth, perinatal and neonatal death and congenital abnormalities (38).
Similar conclusions were reached in a study conducted in Norway in which over 68,000 women were given questionnaires to complete during weeks 17 and 30 of their pregnancy and when their child was 6 months old. One thousand and twenty women reported using ginger during pregnancy. No differences were found between women who had been exposed to ginger during pregnancy and those who had not with regard to the risk of congenital malformations, stillbirth/perinatal death, preterm birth, low birth weight, or low Apgar score. However, compared to controls, a higher percentage of the women who took ginger after week 17 experienced vaginal bleeding (7.8% versus 5.8%, p=0.007). When the investigators looked specifically at vaginal bleeding that was more than spotting, the association was no longer significant (39).
A double-blind, randomised controlled trial lasting seven days in 170 pregnant (<16 weeks gestation) women indicated that ginger 500mg twice daily is as effective, but slower than dimenhydrinate 50mg twice daily to take effect in the treatment of nausea and vomiting during pregnancy. Over the course of the study, the mean nausea score (measured by participants using a visual analogue scale) decreased in both groups, but no statistically significant difference in score was seen between the two groups. Drowsiness and heartburn were noted in both groups, the incidence of drowsiness being significantly higher in the dimenhydrinate group (78% versus 6%, p<0.01). No additional adverse effects are reported but follow up was only for one week (40). Dimenhydrinate is only available in the UK in combination with cinnarizine in a preparation licensed to treat vestibular disorders in adults (41).
Ginger 650mg three times a day was found to be more effective than vitamin B6 25mg three times a day in 123 pregnant (≤16 weeks gestation) women. Participants in this study received their treatment at home for four days and then returned to antenatal clinic for follow up. Side-effects reported in the ginger group were heartburn (n=8), sedation (n=7) and arrhythmia (n=1) (no further details reported). Two and eleven patients in the vitamin B6 group also experienced heartburn and sedation, respectively (42).
Concern has been raised that the thromboxane synthetase inhibitory action of ginger could affect testosterone receptor binding (43) thereby possibly altering sex steroid differentiation of the foetal brain (44). Ginger also has limited potential to stimulate uterine smooth muscle (45). Despite these theoretical concerns, the risk posed by ginger to the foetus is considered to be low (43), particularly when it is used at the doses found in foods (45). However, it has been suggested that doses of ginger higher than 1g/day should be avoided during pregnancy (45).
Ginseng (Panax)
Little information is available on the safety of ginseng during pregnancy in humans (or animals) and further data are warranted (46). In non-pregnant patients, hypertension and hypoglycaemia have been reported with ginseng and these effects could complicate pregnancies with hypertensive disorders or diabetes (46). It is possible that ginseng has oestrogen-like properties (47) and is therefore not recommended during pregnancy (48).
A study in which 88 women who had taken ginseng during pregnancy were matched with 88 controls, found no statistically significant differences between groups in birth weight, mode of delivery, preterm delivery, low Apgar scores, stillbirths or neonatal death. No mention was made of congenital malformations (49).
Pregnancy outcome was reported for 149 cases of exposure to ginseng during the first trimester of pregnancy (50). In 116 of these cases, foetal exposure was to ginseng alone. Of the children born to women who had taken ginseng alone during the first trimester, six had malformations, but evaluation by individual defect category did not indicate that the risk of malformation was significantly higher than that in a control group in which herbal medicines had not been used (50,51). It is interesting to note that in traditional Chinese medicine ginseng is contraindicated in pregnant and lactating women except in the treatment of specific conditions (51).
There is one report of androgenisation in a neonate exposed to ginseng in the womb and through breastfeeding (52), however the cause of the androgenisation was later reported to be most likely caused by the mother taking Periploca sepium (silk vine) rather than ginseng (53). Therefore causality has not been established.
Green Tea
There is limited evidence regarding the use of green tea during pregnancy (54). Large quantities of green tea should be avoided by pregnant women because of their caffeine content (54,55). Caffeine crosses the placenta producing foetal blood concentrations similar to maternal levels (54). The Food Standards Agency advises pregnant women not to consume more than 200mg caffeine per day because higher caffeine intakes might cause miscarriage or low birth weight (56).
Iron-rich herbs
During pregnancy the need for iron increases and may not be sufficiently covered by food or maternal iron stores (57). Several different preparations of iron-rich herbs are available. The quantity of iron found in these products may vary greatly and the risk of contaminants cannot be ruled out. If a patients thinks they may be iron deficient then this should be verified by their doctor who can prescribe appropriate treatment.
Peppermint
Some sources suggest that peppermint in large doses during pregnancy might have an emmenagogue (stimulating menstruation) and abortifacient effect (58, 59). Peppermint has been traditionally used for hundreds of years; one source suggests that in the absence of medical literature reporting adverse effects, that there is little risk from the typical use of this herb in pregnancy (59). Given the lack of published information to support the use of therapeutic doses of peppermint oil during pregnancy, the UK Teratology Information Service does not recommend its use during this period unless there is a compelling clinical need (60).