Morning sickness is such a common early pregnancy symptom that it’s thought to affect 85% of pregnant women. But scientists have no singular explanation for why it affects so many people—and why some sail through unscathed.
What is well understood is that nausea and vomiting can take a toll, and while various nutrients and herbal remedies may help (like vitamin B6 and ginger), a new study has found that taking probiotics may significantly reduce symptoms of morning sickness in the first and second trimester.
Morning sickness and the microbiome
Probiotics are beneficial bacteria that colonize the gut lining. In pregnancy, a time of major hormonal shifts, elevated levels of estrogen and progesterone can change the microbiome composition, directly affecting how the gastrointestinal tract functions. It can mean a marked difference in which foods you want to eat—and which you can no longer stomach, likely as a result of the nausea, vomiting and constipation that can ramp up quickly.
Morning sickness can start as early as week 6 of pregnancy and can last as long as week 22, says Dr. Ranae Yockey, a board-certified obstetrician and gynecologist and program director of the midwifery services at Northwest Community Hospital, to Motherly.
Read more: When does morning sickness start?
But the effects of taking probiotics on morning sickness had never been examined—until now. In a study led by researchers at University of California Davis, 32 participants who were between 14 and 21 weeks pregnant took a probiotic supplement twice daily for six days, then took two days off, and repeated the cycle once more. The study lasted 16 days and was published in the journal Nutrients.
The probiotic supplement used in the study consisted of 6 strains, but most were of the Lactobacillus species, which has been well studied for its beneficial GI effects.
By asking participants to record their symptoms 17 times per day for the duration of the study, the researchers were able to assess if probiotics reduced instances of nausea and vomiting, as well as constipation and time spent feeling nauseated. They also asked participants to rate their quality of life.
Probiotics use was associated with lower levels of morning sickness
Though the sample size was small and the study was short in duration, the results were impressive: Probiotic intake reduced episodes of nausea by 16%, reduced the hours participants spent feeling nauseated by 16%, and reduced vomiting episodes by 33%. Constipation was also improved, and study participants reported a higher quality of life in general, noting that they had less fatigue and were better able to manage their work and social commitments.
“Nausea, vomiting and constipation during pregnancy can significantly diminish the quality of patients’ lives. Once nausea and vomiting during pregnancy progress, they can become difficult to control, and sometimes the patient even needs to be hospitalized,” says Albert T. Liu, lead author for the study and a professor of obstetrics and gynecology, in a press release.
Related: 5 ways to protect your baby’s microbiome after birth
The researchers also analyzed fecal matter from participants both before and during the study, and found that those whose fecal matter contained lower amounts of bacteria carrying bile salt hydrolase, an enzyme that makes bile acid to help absorb nutrients in the digestive tract, had more pregnancy-related vomiting. Taking probiotics increased levels of the bacteria that produce bile salt hydrolase, which may explain the mechanism behind why the probiotics were correlated with less vomiting.
They also found that vitamin E levels were associated with lower vomiting levels, and that taking probiotic supplements increased vitamin E levels in fecal matter.
“This research provides key insights about the impact of gut microbes on gastrointestinal function during pregnancy. Our gut microbiota explains why we [eat] what we eat, and why bacteria-generated metabolites and products have a huge impact on our health,” says Vice Chair for Research Yu-Jui Yvonne Wan, a professor in the Department of Pathology and Laboratory Medicine and senior author on the study, in a press release.
Are probiotics safe for pregnancy?
While there isn’t a lot of data on their usage in pregnancy, probiotics are generally considered to be safe for use in pregnancy and lactation. “There is no reason they shouldn’t be used—they are going to stay in the gastrointestinal tract, not affect the baby in the uterus,” says Mary Jane Minkin, MD, an OB-GYN and clinical professor of Obstetrics, Gynecology and Reproductive Sciences at Yale University School of Medicine.
But because the research on the benefits of probiotics for use in pregnancy is limited, if you have significant nausea and vomiting, be sure to check in with your birth provider to discuss treatment options, suggests Dr. Minkin.
Probiotics may confer other benefits throughout pregnancy and birth, too, not just in the early stages. They have been shown to prevent some infections in pregnancy and prevent preterm delivery.
Dr. Minkin notes that where probiotics could be especially helpful for prenatal health is when they’re used before conception. “There is some literature that shows that a condition known as bacterial vaginosis [BV] can lead to preterm labor. However, there is good data to show that it is best to tend to this problem before pregnancy. One measure that can help is to use probiotics which are vagina-friendly pre-pregnancy. And one probiotic that women can turn to is Pro-B, to try to reduce the incidence of getting repeat episodes of BV,” she notes.
“So before pregnancy for someone with a history of recurrent bacterial vaginosis, treating with Pro-B may well be advantageous.”
Here are a few of our favorite probiotics
Mary Jane Minkin, MD, is an OB-GYN and clinical professor of Obstetrics, Gynecology and Reproductive Sciences at Yale University School of Medicine.
Baldassarre ME, Palladino V, Amoruso A, Pindinelli S, Mastromarino P, Fanelli M, Di Mauro A, Laforgia N. Rationale of probiotic supplementation during pregnancy and neonatal period. Nutrients. 2018 Nov;10(11):1693.
Elias J, Bozzo P, Einarson A. Are probiotics safe for use during pregnancy and lactation?. Can Fam Physician. 2011;57(3):299-301.
Liu AT, Chen S, Jena PK, Sheng L, Hu Y, Wan Y-JY. Probiotics Improve Gastrointestinal Function and Life Quality in Pregnancy. Nutrients. 2021; 13(11):3931. doi:10.3390/nu13113931