The purpose of the study is to investigate if the probiotics Vivomixx® can affect gestational weight gain, microbiota and pregnancy complications in pregnant obese women and birth weight body composition of their infants.

Accumulating evidence indicates that the gut microbiota plays a significant role in obesity and because the "ideal" composition of the gut microbiota remains poorly understood, modulation of the gut microbiota composition represents a potentially attractive treatment option against excessive gestational weight gain and adverse outcomes for obese pregnant women and their newborn. Dietary supplements in the form of probiotics could be an efficient treatment for controlling weight gain in pregnancy by inducing changes in the gut microbiota and could have influence on infant's microbiota, which could have important implications for infant development and health.

A pilot study including 50 obese pregnant nulliparous with BMI between 30-35 kg/m2 will, after accepting participation, be randomized to receive daily placebo or probiotics (four capsules of Vivomixx®; total of 450 billion CFU/day) from gestational age 14-20 until delivery. The infants will be followed until 9 months of age. Shortly after birth, tissue composition will be measured in the infants by DEXA-scanning. The women will be monitored by weight, blood-, fecal- and urine samples, diet questionnaires and hospital record review. Vivomixx® is a probiotic mixture of 8 probiotic strains, (Bifidobacterium breve, Bifidobacterium longum, Bifidobacterium infantis, Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus paracasei, Lactobacillus bulgaricus and Streptococcus thermophilus).

This is the first pilot study in which the probiotic Vivomixx® are added in a randomized fashion to the standard of care in obese pregnant women. 50 pregnant women are planned to be included. The aim of this group size is to clarify the feasibility, compliance and to estimate parameters such as the standard deviation which will be used in a sample size calculation for a full-scale trial.

Inclusion Criteria:

• BMI ≥ 30 and ≤35 kg/m2- calculated from pre-pregnancy weight
• Primiparous singleton pregnancy
• Able to read and speak Danish
• Normal ultrasound scan of the fetus at gestational age 12-14
• Oral glucose tolerance test at gestational age 14-20

Exclusion Criteria:

• Pregnancy at > 20 weeks gestation at recruitment
• Pre-gestational diabetes or other serious diseases
• Multiple pregnancy
• Previous bariatric surgery
• Ingestion of probiotics < 1 month before the inclusion or ingestion of other kinds of probiotics than the study probiotics