Fennel

Pregnancy

The 2015 Trabace et al. study was retrospective and observational. It interviewed 630 expectant mothers after childbirth and considered 600 interviews; fennel was among the herbs used during pregnancy. Its abstract states that regular fennel use resulted in shorter gestational age, but does not establish cause, dose, exact timing, or a trimester-specific estimate. The EMA assessment report gives fennel subgroup counts and mean comparisons that are absent from the primary abstract; those exact figures are not verified against the primary study and are omitted from the period summaries. The 2019 Shayan et al. study assigned 24 pregnant mice to four groups and gave aqueous fennel extract by oral gavage from gestational day 6 to day 15; dose-related fetal changes were reported. This concentrated animal extract is not evidence about ordinary seasoning or human pregnancy. EMA's 2026 decision says pregnancy safety has not been established and medicinal use is not recommended; Swissmedic also advises against use in pregnancy.

Breastfeeding

LactMed describes fennel as a traditional galactagogue and summarizes small studies with different products and outcomes. Ghasemi et al. (2014) randomized 78 mother-infant pairs; the intervention was 7.5 g fennel seed powder plus 3 g black tea three times daily for four weeks, compared with black tea alone, and outcomes included infant growth and feeding signs rather than direct milk-volume measurement. Vafaei et al. (2018) tested 3 g fennel syrup daily for 15 days; the abstract reports 69 pairs but allocates 35 to each group, and the adjusted prolactin difference was not significant (P-value=0.76); milk volume was not measured. Wagner et al. (2019) randomized 60 fully breastfeeding mother-infant pairs to a multi-herb tea containing fennel, anise, coriander, fenugreek, and other herbs or a placebo tea; the abstract reports no adverse effects attributable to the interventions, but the result cannot be assigned to fennel. A 2026 single-group pre/post study enrolled five mothers and tested one 2 g fennel tea bag daily for four weeks; without a control group and with inconsistent table values, it cannot establish cause. Hausner et al. (2008) detected trans-anethole in milk after a 100 mg capsule exposure; that was not a fennel-tea transfer study. Turkyilmaz et al. (2011) tested fenugreek tea, not fennel, and is excluded as fennel-specific evidence. LactMed cites an older case report whose publisher record has no abstract; its case details and fennel's role are not verified and are not repeated in the public summary.

What was tested

Pregnancy evidence includes one retrospective human cohort and one mouse study of concentrated aqueous extract by gavage. Lactation studies include fennel seed added to black tea, a fennel syrup trial measuring prolactin, and a multi-herb tea trial measuring maternal and infant outcomes. The 2026 study tested a once-daily 2 g fennel tea for four weeks in five mothers without a control group. A trans-anethole capsule study measured transfer into milk but did not test fennel tea. A completed registry record describes 1 L fennel infusion daily for seven days in a single group of 22 participants; the registry has no posted results section. Ordinary seasoning and fennel essential oil were not tested in these trials.