“…The 45 articles included investigated 14 470 pregnant women in total, of which 13 757 underwent normal full-term pregnancies, 145 experienced spontaneous preterm deliveries, 536 experienced spontaneous abortions, and 32 had performed an induced abortion. The study populations were from Europe ( n = 4639) [ 13 , 22 , 27 , 28 , 32 , 38 , 40 , 42 , 43 , 45 , 47 , 51 , 58 – 60 , 62 – 64 , 66 , 67 ], Asia ( n = 7116) [ 23 , 34 , 35 , 37 , 39 , 41 , 46 , 52 , 55 , 57 , 61 ], USA ( n = 1681) [ 18 , 20 , 21 , 29 , 48 , 53 , 56 , 65 , 68 ], and Latin America ( n = 1034) [ 36 , 44 , 49 , 50 , 54 ]. Table 1 shows demographic characteristics, key aspects of study design, and study strength and potential biases of all included studies.…”