A 2025 human study investigated placental and breast milk sulforaphane content:

“Uncomplicated pregnant patients (n = 8) scheduled for elective caesarean sections (>37 weeks gestation) provided written and informed consent. A single oral dose of EnduraCell, a broccoli sprout extract (equivalent to 21 mg of sulforaphane), was administered prior to caesarean section. Baseline blood pressure, blood and urine were collected and again at time of operation, alongside umbilical cord blood (vein and artery) and placental samples.

2–4 days post-delivery, a second dose was administered. Two hours later, maternal bloods and breast milk were collected.

Unlike in the maternal circulation, sulforaphane levels did not show an obvious peak at the 2–3 h timepoint in the fetal umbilical vein serum and plasma or the umbilical artery serum and plasma.

A linear regression indicated that the percentage of fetal sulforaphane relative to the maternal concentration increased over time, showing progressive transfer from maternal to fetal circulation.

This is the first study to demonstrate the successful maternal-fetal transfer of sulforaphane through the placenta and into breast milk following exposure to a broccoli sprout extract during and after pregnancy. No adverse events or outcomes were reported from any of the participants, supporting the reassuring safety profile of an acute exposure to a broccoli sprout extract in pregnancy.

https://www.sciencedirect.com/science/article/pii/S0143400425006964 “Assessing the transplacental passage and breastmilk levels of broccoli sprout-derived sulforaphane”

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1. These researchers incorrectly termed a commercially available broccoli sprout powder as an extract. Grinding up broccoli sprouts produces a different product than does processing broccoli seeds or sprouts using solvents into extracts.

2. They asserted the broccoli sprout powder was a 21 mg sulforaphane dose. A more realistic explanation should have been provided, since:

• No sulforaphane measurements were taken to back their assertion, which is understandable because the powder contained glucoraphanin, sulforaphane’s precursor, and sulforaphane wouldn’t be expected to be found in the powder; and
• Conversion of broccoli spout powder to sulforaphane would be dependent on each subject’s gut microbiota, which is different for each individual.

Here’s what How long does sulforaphane keep? said for the same broccoli sprout powder product:

“Per the manufacturer, each capsule contained 700 mg of 100% whole broccoli sprout powder, including active myrosinase and 21 mg of glucoraphanin, which upon full conversion to SFN would yield ∼8 mg, equaling ∼24 mg of SFN total per three-capsule dose. We note that full conversion to SFN, even with active myrosinase in the supplement, is not expected.”

3. Characterizing this minimal dose as “an acute exposure” mixed up its meaning with the common meaning of acute – “extremely sharp or severe; intense.”

4. Someday, researchers will be interested and forward-thinking enough about their field to plan ahead and investigate occurrences such as why both the highest and lowest maternal blood sulforaphane content didn’t translate into correspondingly ranked umbilical cord blood sulforaphane content.

5. Since blood contains up to 18,000 compounds, I don’t see where any other maternal blood compound wouldn’t pass to the fetus, unless it is definitively shown that the placenta specifically blocks it. It’s time to discard and disclaim any “safe and effective” propaganda with respect to pregnant women and breastfeeding mothers.

I found this study by it citing Eat broccoli sprouts for longevity.