Although a new baby is eagerly awaited, no one wants it coming too soon.

Preterm birth (PTB) is never good. An estimated 15 million babies worldwide are born prematurely, which can result in disability and even death.

Delaying the delivery via tocolysis (labor suppressants) is the usual option but risks can ensue for both mother and child. A review titled Prenatal Probiotics: A Way Forward in Prevention of Preterm Birth published in Journal of Clinical Gynecology and Obstetrics in 2019 does an excellent job of describing the intricacies.

The newest strategy is identifying the causes and trying to eliminate them.

This is where microbes enter the picture. Infection or inflammation contributes to up to 30% of PTBs. Indeed, one meta-analysis involving 20,232 women showed that the risk of PTB doubles in women with bacterial vaginosis (BV) at less than 37 weeks of gestational age.

There is growing evidence for the usage of probiotic to prevent PTB. First, let’s take a look at what is considered normal microbiota.

Healthy vaginal microbiota

The healthy human vagina is dominated by Lactobacilli during reproductive years and pregnancy; rising estrogen levels account for their presence.

These particular bacteria are highly effective for several reasons:

  • Lactobacilli maintain a good pH of the vaginal tract
  • Lactobacilli produce lactic acid and hydrogen peroxide to boost immunity

The difference in vaginal health is striking: Women who have hydrogen peroxide producing strains of Lactobacilli have only a 4% prevalence rate of BV compared with 32% in women colonized by non hydrogen peroxide producing strains and 56% in those without Lactobacilli .

Abnormal microbiota

Abnormal vaginal microbiota and bacterial vaginosis (BV) are important risk factors for PTB and premature rupture of membranes. In women with BV, a harmful dysbiosis results from changes in the vaginal microbiome. Pathogens move in and colonize, overwhelming the lactobacillus population. One study found that pathogens associated with BV such as Prevotella, Sneathia, and Gardnerella are rarely found in women who deliver at term.

Bacterial vaginosis and preterm delivery

How do pathogens lead to a premature birth?

Pathogens may:

  • Spark inflammation in the endometrium, making the intrauterine environment incompatible for embryo implantation and placental development
  • Produce enzymes that elevate prostaglandin levels which induce changes in the fetal membranes. This devious process leads to uterine contraction and preterm labor
  • Secrete endotoxins such as lipopolysaccharides (LPSs) which trigger a complex cascade of changes leading to premature birth

At this point in the infection, antibiotics (most commonly metronidazole and clindamycin) are prescribed as they have been for many decades. However, antibiotics are obviously not ideal as they will not spare needed healthy bacteria which can lead to relapse. In addition, prolonged uses of antibiotics can cause drug resistance and, in some cases have increased the incidence of PTB.

Therefore in this era of multidrug-resistant bacteria, it is important to look for an alternative and effective method for the prevention of PTB.

Probiotics in preterm birth

Probiotics are increasingly considered a better remedy.

A number of clinical trials with probiotics have confirmed that probiotics are both safe and effective for the prevention or treatment of numerous infectious and or inflammatory dis eases in both pregnant and non-pregnant women. They also reduce the recurrence of BV by increasing the colonization of Lactobacilli in the vagina.

Lactobacilli appear to be effective against dysbiosis: they multi-task by:

  • Producing lactic acid which lowers pH effectively killing off pathogens
  • Making bacteriocins, collagen-binding proteins and hydrogen peroxide which inhibit growth and adhesion of harmful endotoxins

The effect of Lactobacilli on the immune system and their vaginal colonization ability are species and strain-specific.

Which strain is best?

Among many strains of Lactobacilli, Lactobacillus rhamnosusGR1 and Lactobacillus reuteri RC14 are found to be highly effective. There are probably more; ProbioticsNow will keep looking but meanwhile here is a link to one product called Pro-Flora.

But both these strains are integral to the female genital tract and are able to colonize in the vagina when administered orally.


Do all you can to prevent a preterm birth.

Promote a healthy vaginal microbiome with a diet high in prebiotics and probiotics. Supplement with Lactobacilli on recommendations of a nutritionist or doctor.