Quick take: Studies in rats and human reports suggested that ginger use during pregnancy does not interfere with embryo development.
Ginger (Zingiber officinale) is a tropical plant the rhizomes of which are used for both culinary and medicinal purposes. Ginger contains monoterpenes and sesquiterpenes, as well as phenolic ketones, mainly gingerols (CAS 1391-73-7) and their derivative shogaols (CAS 555-66-8). Ginger, a very common ingredient in traditional Chinese herbal formulas, has been used to treat gastrointestinal disorders, arthritis, and many other conditions. As occurs with many herbal medications, there appears to be large variation in the composition of many ginger root preparations (10).
Ginger is a thromboxane synthase inhibitor in vitro (3). Thromboxane synthesis inhibition would be expected to affect platelet aggregation, but clinical studies specifically designed to assess the effect of ginger on bleeding risk (4,5,6) have found no effect of up to 15 g raw ginger, 40 g cooked ginger, or 4 g dried ginger daily on platelet aggregation; however, dried ginger 10 g/day decreased platelet aggregation (4). There are clinical reports (19) and in vitro studies (20) indicating that ginger might have anticoagulant effects. One commentator expressed concern about this potential pharmacological action during pregnancy (21).
Experimental animal development
Female rats given 100, 333, or 1000 mg/kg/day of a commercial ginger extract by gavage on days 6-15 of gestation showed no effect on food consumption or maternal weight gain and no effect on fertility index (ratio of pregnant to mated females), pregnancy index (ratio of females with viable fetuses to mated females), weight of the gravid uterus, placental weight, numbers of fetuses per litter, numbers of early or late resorptions, numbers of implantations, corpora lutea, preimplantation losses or postimplantation losses (7). No differences in fetal body weight or sex ratio were noted. The authors of this study stated that there were differences in skeletal development but did not show statistically significant differences in skeletal end points.
In another study, pregnant Sprague-Dawley rats were given ginger tea made with 20 g/L or 50 g/L ginger via drinking water (8). No maternal toxicity was noted. There were no significant differences in resorptions per litter or number of litters with resorptions, but the four animals with resorption of all embryos were in ginger-treated groups. No gross morphologic malformations were seen in treated fetuses. Fetuses exposed to ginger tea weighed significantly more than controls, an effect independent of litter size. Skeletal variations were similar between exposed and control fetuses, but exposed fetuses also had more advanced skeletal development than controls, consistent with their higher weights.
The thromboxane synthase inhibitor action of ginger led one researcher to speculate that ginger might affect testosterone receptor binding and alter sex steroid differentiation of the fetal brain (3). Two studies of ginger in rats showed no difference in sex ratio and normal development of genitalia (7,8).
In a clinical trial, pregnancy outcomes were assessed in 27 women (1). One patient in the ginger group experienced a spontaneous abortion and one patient in the placebo group underwent induced abortion. Twenty-five patients went to term and all infants were normal in appearance, birthweight, and Apgar scores (1). In a prospective study based on women contacting a Canadian teratology information service, no significant increase in adverse outcomes was detected in a population of 187 women who reported using ginger in early pregnancy (11). The Norwegian Mother and Child Cohort study identified 1020 women who retrospectively reported using ginger during gestation (18). No increase in adverse outcomes was detected when comparisons were made with unexposed controls. A case control study from the National Birth Defects Prevention Study did not identify an association between ginger therapy during pregnancy and facial clefts, neural tube defects, or hypospadias (16).
A 2003 review found that neither ginger nor other alternate treatments were effective in the treatment of hyperemesis gravidarum (12). A 2007 report from Thailand on the effectiveness of ginger for treatment of nausea and vomiting in pregnancy did not seem to be placebo-controlled (13). Two other double-blind, randomized, placebo-controlled trials have suggested that dried ginger root in doses up to 1 g/day may be an effective treatment for mild hyperemesis during pregnancy (1,2). An Australian study compared the effectiveness of ginger (1.05 g/day) with vitamin B6 (#1190, 75 mg/day) in groups of 145 women <16 wk gestation (14). Neither agent was effective at reducing nausea, retching, or vomiting. There was no difference in pregnancy outcomes except that the ginger group had slightly more live births. A 2013 review of 4 studies that included randomized controls to evaluate the safety and effectiveness of ginger for the treatment of nausea and vomiting in pregnancy concluded that ginger was effective for this indication (17). This review did not find that use of ginger in early pregnancy increased risk of adverse outcomes but brought attention to the limited data on the maximum safe dose of ginger and appropriate duration of treatment (17). There was no increased risk of major malformations among 159 pregnant Korean women who used dried ginger as a medication when compared to a control group of 306 pregnant women (22). An increase in stillbirth among treated women was more prominent when treated women were compared to the general population of South Korea (odds ratio 7.9, 95% CI 2.9-21.4, p < 0.0001). Comparison to a population control rather than a contemporaneous control detracts from the reliability of this finding. There was variability in dose of ginger, and there were exposures to other herbal medicines (22).
A daily dose of 1000 mg dried ginger given to lactating mothers for seven days postpartum increased milk volume on day 3 of treatment but not on day 7 (23). There was no effect of ginger on serum prolactin concentration.
Ginger aromatherapy apparently has an aphrodisiacal effect on fruit flies. Male Mediterranean fruit flies exposed to ginger root essential oil outcompeted unexposed males in obtaining matings (9). Ginger contains alpha-copaene, a known male attractant. A small study in diabetic male mice suggested that Ginger root might increase fertility index, serum testosterone #1629, and testis, seminal vesicle, and prostate weight and might improve semen quality (15).
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