Is kefir safe during pregnancy?

What does the evidence say about kefir during pregnancy?

1. Unpasteurized milk and raw milk products are named among the foods that carry listeria, and fermentation is not a substitute for the pasteurization step. 1
2. Pregnancy carries a crude listeriosis incidence roughly 10 to 100 times that of the general population, and maternal symptoms are often subtle or absent even when the infection is serious. 2
3. Probiotics are live microorganisms found in yogurt and other fermented foods, and while some uses look promising, in most cases it is still unclear which ones help and which do not. 3
4. A case-control study of 249 pregnancies found probiotic yogurt intake during pregnancy associated with lower odds of gestational diabetes, with the authors cautioning that self-reported intake and study design mean intervention trials are still needed. 4
5. Kefir measures around 3.1 grams of lactose per 100 grams, lower than unfermented milk, because the culturing process breaks some of it down. 5

Is kefir safe in each trimester?

• First trimester. If you are already drinking kefir, read the bottle now rather than later. Fermenting raw milk does not undo the raw milk problem, and first-trimester listeria infection carries the highest chance of loss.
• Second trimester. Kefir made from pasteurized milk is a reasonable way to get calcium and some vitamin D if plain milk has stopped appealing. Home-brewed kefir is only as safe as the milk it started from, so use pasteurized milk if you culture your own.
• Third trimester. Keep it cold and finish bottles within their date. Kefir keeps fermenting slowly in the refrigerator, which is normal, but a bottle that has been open for weeks is not worth drinking now.