Synbiotics are beneficial in case of gestational diabetes.
Ahmadi S, Jamilian M, et al. The effects of synbiotic supplementation on markers of insulin metabolism and lipid profiles in gestational diabetes: a randomised, double-blind, placebo-controlled trial. Br J Nutr. 2016 Sep 29:1-8.
Babies born via Cesarean delivery may have a different intestinal flora up to the age of 7.
 Grönlund MM, Lehtonen OP, Eerola E, et al. Fecal microflora in healthy infants born by different methods of delivery: permanent changes in intestinal flora after cesarean delivery. J Pediatr Gastroenterol Nutr. 1999; 28(1):19–25.
 Salminen S, Gibson GR, McCartney AL, et al. Influence of mode of delivery on gut microbiota composition in seven year old children. Gut. 2004; 53(9):1388–9.
Normal vaginal microflora is best restored and maintained by Lactobacillus rhamnosus and L. reuteri.
A double-blind, placebo controlled study by Reid et al found that 32 healthy women displayed a significant increase in the amount of lactic acid bacteria in the vagina after oral supplementation of L.rhamnosus GR-1 and L.fermentum RC-14 bacteria, as compared to the placebo group. The study lasted 2 and 4 weeks. The 64 subjects of the study displayed signs of asymptomatic bacterial vaginosis, but after 2 and 4 weeks of the study their vaginal microflora was rated as normal on the Nugent score. The placebo group displayed significantly less improvements. A similar result was demonstrated in another double-blind study by the same author where 59 subjects were given the same strain of bacteria or a placebo. 
 Reid G, Charbonneau D, Erb J, Kochanowski B, Beuerman D, Poehner R, Bruce AW. Oral use of Lactobacillus rhamnosus GR-1 and L. fermentum RC-14 significantly alters vaginal flora: randomized, placebo-controlled trial in 64 healthy women. FEMS Immunol Med Microbiol. 2003 Mar 20;35(2):131-4.
Bifidobacterium lactis help treat constipation.
In a 2-week study involving 100 subjects (average age – 44), one group received a dose of B.lactis (17.2 billion CFU, n=33), one received a low dose (1.8 billion CFU, n=33), and one was a placebo group (n=34). After 2 weeks the overall intestinal transit time, i.e. the time it takes for the intestines to empty, had significantly decreased in the two B.lactis groups, while remaining unchanged for the placebo group. 
Probiotics speed up intestinal transit because they reduce the formation of methanogens, which can hinder intestinal transit by producing methane, which, in turn, blocks intestinal motor function or motility. It has been found that people with slow intestinal transit have more methane producing bacteria in the intestines as compared to healthy individuals. Furthermore, probiotics promote fermentation processes in the intestines thus boosting the peristalsis, i.e. the frequency of contraction, of the large intestine thus speeding up transit time. 
 Waller PA, Gopal PK, Leyer GJ, Ouwehand AC, Reifer C, Stewart ME, Miller LE. Dose-response effect of Bifidobacterium lactis HN019 on whole gut transit time and functional gastrointestinal symptoms in adults. Scand J Gastroenterol. 2011 Sep;46(9):1057-64.
Saccharomyces boulardii reduce risk of diarrhea when travelling or beginning kindergarten.
A summary of 12 double-blind, placebo controlled studies shows that probiotics are a promising preventive treatment for traveler’s diarrhea. A combination of Saccharomyces boulardii and two probiotic bacteria - Lactobacillus acidophilus and Bifidobacterium bifidum – has been shown to be very effective.  Incidence of traveler’s diarrhea in the groups using S.Boulardi was 5-11%.  
To date the most extensive study on the positive effects of Saccharomyces on traveler’s diarrhea has been carried out by Kollaritsch et al. The main conclusion – probiotics are an effective preventive treatment. If used approximately one week prior to travelling, they can reduce the risk of contracting traveler’s diarrhea. One study involved 1231 Austrian tourists travelling to exotic destination. They took a dose (250 or 500 mg) of S.boulardii or a placebo over a course of three weeks. The tourists began the course of probiotics 5 days prior to travelling and continued it throughout the holiday. Traveler’s diarrhea was experienced by 43% of the placebo group, but incidence was significantly less in the 250 mg S.boulardii dose group (34%) and the 500 mg group (32%). Another study by Kollaritsch et al involving 1016 Austrians travelling to Northern Africa, the Middle and the Far East, subjects were given 250 mg/d (5 × 109) S. boulardii, 1000 mg/d (2 × 1010) S. boulardii or a placebo, and they began taking the doses 5 days prior to travelling. S.boulardii significantly reduced the number of tourists who experienced traveler’s diarrhea: 39% of the placebo group, but only 34% of the 250 mg S. Boulardii group and 29% or 500 mg S. Boulardii group were afflicted (P < 0.05).
 Kollaritsch H, Kremsner P, Wiedermann , G , Scheiner O. Prevention of traveller’s diarrhea: comparison of different non-antibiotic preparations. Travel Med Internatl. 1989;7:9–18.
 Kollaritsch H, Holst H, Grobara P, Wiedermann G. [Prevention of traveler's diarrhea with Saccharomyces boulardii. Results of a placebo controlled double-blind study] Fortschr Med. 1993;111:152–156