Fig. 1.

Overflow of sample selection criteria. 6211 women from the cohort were genotyped and 5968 women passed the genotyping quality control. We then applied the selection criteria (gestational age at enrolment <14 weeks or difference between LMP dating and USG dating <7 days, participant's age ≥18 years, only spontaneous singleton live birth without any complications) on these 5968 women and 4682 women were selected among which 521 had spontaneous preterm delivery (<37 weeks) while 4161 had term delivery (≥37 weeks – ≤41 weeks). Next, we matched preterm and term delivering women in 1:2 ratio based on age, BMI, parity and occupational status for the association analysis.