. 2019 Oct 9;22(1):114–125. doi: 10.1177/1099800419880615

Table 1.

Study Characteristics.

Author(s)	PICO Statement	Participants and Comparison Groups	Definition of Prepregnancy BMI and Obesity	Time Point for Microbiome Collection	Sample Source^a	Quality Assessment^b
Biospecimens collected from mothers only
Collado et al. (2008)	Do BMI and GWG alter the maternal gastrointestinal microbiota before delivery?	N = 54 women: n = 18 OW (called OW in study but defined as OB according to post-2008 guidelines) n = 36 NW Groups: OW and NW	BMI: Maternal self-report of weight at first clinic visit Overweight/obesity: BMI > 30 kg/m²	First (10–15 weeks’ gestation) and third (30–35 weeks’ gestation) trimesters of pregnancy	Study	IIB
Houttu et al. (2017)	Does the degree of overweight alter the composition of the maternal gastrointestinal microbiome during pregnancy?	N = 99 women n = 52 OW n = 47 OB Groups: OW and OB	BMI: Maternal self-report of weight at first clinic visit Obesity: BMI > 30 kg/m²	< 17 weeks’ gestation	Study	IIB
Gomez-Arango et al. (2016a, 2016b)	Is there a difference in gut microbiome composition and circulating metabolic hormones between OW and OB pregnant women?	N = 70 women n = 29 OW n = 41 OB Groups: OW and OB	BMI: not reported Obesity: BMI > 30 kg/m²	16 weeks’ gestation	Study	IIB
Santacruz et al. (2010)	Do body weight and GWG^c alter the composition of the maternal gastrointestinal microbiome during pregnancy?	N = 50 women n = 34 NW n = 16 OW Groups: NW and OW/OB	BMI: not reported Obesity: BMI > 25 kg/m²	24 weeks’ gestation	Study	IIB
Smid et al. (2018)	Does EGWG change the maternal gastrointestinal microbiome during pregnancy?	N = 31 women Groups: Above and below median GWG for this cohort, baseline and follow-up	BMI: Weight at first clinic visit Obesity: BMI > 30 kg/m²	Baseline: < 20 weeks’ gestation Follow-up: 36−39 weeks’ gestation	Study	IIIB
Biospecimens collected from mothers and infants
Chu et al. (2016)	Does maternal obesity alter the neonatal and infant gut microbiome in early life?	N = 157 women, 157 infants Groups: High fat intake and control	Not reported	First maternal and infant stool samples at 24−48 hr after delivery and second sample at 4−6 weeks of life	Study	IIB
Stanislawski et al. (2017)	Is maternal prepregnancy overweight/obesity associated with differences in the maternal gastrointestinal microbiota at the time of delivery or in the gastrointestinal microbiota of their infants during the first 2 years of life?	N = 169 women, 181 infants Groups: NW and OW/OB mothers	BMI: Maternal self-report of weight at first clinic visit Overweight and obesity: BMI ≥ 25 kg/m²	Maternal sample 4 days after delivery, newborn samples at 6 time points over the first 2 years of life	Biobank	IIA
Biospecimens collected from infants only
Collado et al. (2010)	Do maternal BMI status and EGWG alter the microbiota of their infants?	N = 42 infants, 26 NW mothers, 16 OW mothers Groups: OW and NW	BMI: Maternal self-report of weight at first clinic visit Overweight: BMI ≥ 25 kg/m²	1 and 6 months of life	Study	IIA
Galley et al. (2014)	Is maternal obesity associated with differences in the composition of the gut microbiome in children in early life?	N = 77 infants, 25 OB mothers, 51 non-OB mothers Groups: OW and OB	BMI: Not reported Obesity: BMI > 30 kg/m²	18–27 months of age	Study	IIB
Mueller et al. (2016)	Is maternal prepregnancy BMI associated with differences in the gastrointestinal microbiota between infants delivered vaginally and those delivered via ECS?	N = 74 neonates n = 18 VD n = 56 ECS n = 31 to OW/OB mothers Groups: VD and ECS	BMI: Not reported Overweight and Obesity: > 25 kg/m²	2 days after delivery	Study	IIB
Robinson et al. (2017)	Is GWG^c associated with changes in infant fecal microbiota composition, bacterial-community richness, and Shannon diversity index?	N = 84 infants Groups: GWG categories	Not reported	<1 year of age	Biobank	IIB

Note. Studies are arranged to highlight the population studied. BMI = body mass index; ECS = elective cesarean section; EGWG = excessive gestational weight gain; GWG = gestational weight gain; NW = normal weight; OB = obese; OW = overweight; PICO = population, intervention, comparison/control, outcome; VD = vaginal delivery.

^aSamples were either sourced directly from a biobank or from a prospective cohort study. ^bThe quality assessment score includes level (Level I = randomized controlled trial or experimental study, Level II = quasi-experimental, Level III = nonexperimental, Level IV = qualitative) and quality assessment (A = high, B = good, or C = low quality) which was adapted from Keim-Malpass, Letzkus, and Kennedy (2015). ^cGWG was defined by the Institute of Medicine guidelines.