Authors, year (Reference number) Study design Sample size Mean age Country Trimester Pregnancy outcomes Confounding factors
Abeysena et al., 2010 [17 ] Prospective cohort 817
Sri Lanka First PTB, LBW, and SGA Not specify
Kumar et al., 2010 [34 ] Prospective cohort 2,027
India First LBW Maternal age, parity, maternal height, maternal weight, BMI, and gestational age
Kidanto et al., 2009 [32 ] Case control 1,721 24a Tanzania First PTB, LBW, and SB Not specify
Zhang et al., 2009 [16 ] Prospective cohort 160,700 NA China First Second Third PTB Maternal age at delivery, education, occupation, parity, folic acid, BMI, time of first prenatal visit, and fetal gender
Zhang et al., 2009 [33 ] Prospective cohort 164,667 NA China First Second Third SB, ND Maternal age at delivery, education, occupation, parity, folic acid, BMI, time of first prenatal visit, and fetal gender
Ren et al., 2007 [12 ] Retrospective cohort 88,149
China First PTB, LBW, and SGA Maternal age, gravidity, education, and BMI
Lee et al., 2006 [29 ] Prospective cohort 248
Korea Third PTB, LBW Not specify
Mamun et al., 2006 [30 ] Retrospective cohort 1,584
Bangladesh Second SB, PD Not specify
Monawar Hosain et al., 2006 [31 ] Prospective cohort 350 NA Bangladesh First LBW Not specify
Levy et al., 2005 [11 ] Retrospective cohort 153,396
Irael First PTB, LBW, and PD Ethnicity, maternal age, placental problems, caesarean delivery, and nonvertex presentation
Little et al., 2005 [15 ] Retrospective cohort 222,614 NA England First STB, ND Prematurity, birth weight
Ronnenberg et al., 2004 [10 ] Prospective cohort 405
China First PTB, LBW Maternal age, height, BMI, education, exposure to dust, noise, passive smoking, work stress, infant gender, and gestational age
Chang et al., 2003 [26 ] Retrospective cohort 918
USA Second Third PTB, LBW Parity, BMI, smoking, preeclampsia, and antenatal care
Hämäläinen et al., 2003 [27 ] Case control 22,799
Finland First Second Third PTB, LBW, SGA, and PD Not specify
Xiong et al., 2003 [28 ] Retrospective cohort 16,936
China First PTB, LBW, and PD Hospital stay, maternal age, maternal education, parity, gestational age at the first prenatal visit, BMI, hypertensive disorder in pregnancy, vaginal bleeding, and prior spontaneous abortion
Martí et al., 2001 [25 ] Case control 543
Venezuela Third PTB Placenta abruption, PROM, previous premature labor, ANC visit, and antenatal bleeding
Zhou et al., 1998 [9 ] Prospective cohort 829
China First PTB, LBW, and SGA Not specify
Onadeko et al., 1996 [24 ] Prospective cohort 4,649 NA Nigeria Third LBW, SB Not specify
Rasmussen and Oian, 1993 [18 ] Retrospective cohort 3,074 NA Norway First Second PTB, SGA Not specify
Knottnerus et al., 1990 [7 ] Prospective cohort 796 27a Netherland Third PTB, LBW Pregnancy induced hypertension