VDR	Vitamin D receptor
GDM	Gestational diabetes mellitus
25(OH)D	25-hydroxyvitamin D
RR	Relative risk
CI	Confidence interval
BMI	Body mass index
GOUH	Gynaecological–obstetrical university hospital
PUMS	Poznan University of Medical Sciences
HbA1c	Glycated haemoglobin
IgG	Immunoglobulin G
Q1–Q3	1st–3rd quartiles
SE	Standard error
qPCR	Quantitative polymerase chain reaction
RT	Reverse transcription