Table 1.
Risk factors of PTB in SSA.
| First Author | Measure of Effect (Precision) | Sociodemographic Factors | Obstetric Factors | Infections and/or Morbidities | Lifestyle or Behavioral Factors | Anthropometric Factors | Treatment-Related Factors | Factors Adjusted for |
|---|---|---|---|---|---|---|---|---|
| Abadiga et al., 2021 [18] | AOR (95% CI) | NR | <2 ANC visits (6.0, 2.7–13.5), PROM (3.6, 1.8–7.1), IPI < 24 months (3.0, 1.8–7.1), lack of supplementation during pregnancy (2.4, 1.5–3.9) | PIH (3.1, 1.8–5.5), anemia during pregnancy (4.2, 2.1–8.3) | NR | NR | NR | Age at marriage, ethnicity, age of mother, husband and mothers occupation, residence, monthly income, time to reach a health facility, mode of delivery, plan of pregnancy, history of abortion, history of DM and hypertension, HIV/AIDS status, anemia during pregnancy, sexually transmitted disease, substance use, parity, the experience of stress, and maternal MUAC |
| Abaraya et al., 2018 [19] | AOR (95% CI) | NR | Previous PTB (6.4, 2.9–13.9), PROM (11.7, 6.2–21.9), <4ANC (4.8, 1.2–19.0), IPI < 24 months (2.7, 1.7–4.5), multiple pregnancies (4.5, 2.4–8.5), previous stillbirth (4.2, 2.0–8.9), APH (8.1, 3.5–18.5) | Preeclampsia (6.6, 3.3–13.4), Anemia (2.7, 1.0–7.01), PIH (6.0, 2.3–15.6) | NR | NR | NR | Number of ANC visits, hemoglobin levels, PIH, PROM, cardiac disease |
| Abdo et al., 2020 [20] | PROM (4.2, 1.4–12.9) | Preeclampsia (5.1, 2.0–13.3) | Age, residence, previous PTB, parity, ANC visits | |||||
| Abebe et al., 2020 [21] | AOR (95% CI) | Adolescence (2.9, 1.5–5.5) | APH (4.9, 1.9–12.9) | PIH (3.0, 1.4–6.6) | NR | NR | NR | Residence |
| Abrams et al., 2004 [22] | AOR (95% CI) | <4 ANC visits (2.6, 1.4–4.8) | HIV infection (5.0, 1.7–14.6) | NR | Weight ≤ 50 kg (2.1, 1.1–4.1) | Not on Malaria prophylaxis (3.3, 1.3–7.9) | Gravidity, age, weight, Anemia, folate supplementation, malaria prophylaxis, malaria infection, CD4 count, placental malaria, syphilis | |
| Adane et al., 2014 [8] | AOR (95% CI) | NR | Previous poor birth outcome (PTB/LBW) (3.10, 1.20–8.36) | NR | NR | NR | NR | Hypertension |
| Adu-Bonsaffoh et al., 2019 [23] | AOR (95% CI) | Age ≥ 35 years (1.5, 1.1–1.9), | <4 ANC visits (5.1, 4.1–6.6), PROM (3.1, 2.2–4.6) | Hypertension (3.3, 2.6–4.2) | NR | BMI ≥ 30 (0.6, 0.5–0.8), | NR | Age, parity, marital status, education, BMI, ANC visits, PROM |
| Agbla et al., 2006 [24] | AOR (95% CI) | Carrying heavy loads > 5 days/week (5.0, 1.4–18.8), walking and carrying heavy loads > 5 days/week (6.9, 1.5–32.2) | NR | NR | NR | NR | NR | Age, education, health problems during pregnancy, twin birth |
| Akintayo et al., 2015 [9] | AOR (95% CI) | Age > 35 years (2.16; 1.36–3.42), | Previous PTB (6.4, 2.5–16.6), unbooked for ANC care (2.5, 1.8–3.6), PROM (11.1, 6.6–18.6), APH (10.9, 4.9–24.1), (32.2, 13.1–79.5) | PIH (6.4, 3.8–10.9) | NR | NR | NR | Parity, socioeconomic status, education, fetal sex, previous history of surgical abortion |
| Akintije et al., 2020 [25] | AOR (95% CI) | NR | ANC visits ≥ 4 (0.22, 0.1–0.5) | NR | NR | NR | NR | Age, parity, marital status, previous cesarean section, type of pregnancy, mode of delivery, living area, sex of the newborn |
| Alhaj et al., 2010 [26] | AOR (95% CI) | NR | Previous PTB (3.2, 1.0–9.8), previous miscarriage (2.1, 1.0–4.5), previous CS (5.4, 1.7–17.3), IPI < 18 months (2.0, 1.3–5.4), Vaginal bleeding (1.3–18.1) | Dental maneuvers (3.7, 1.1–11.8) | NR | BMI < 25 (3.0, 1.0–8.3), BMI > 30 (3.1, 1.0–9.0) | NR | History of malaria, miscarriage and PTB, CS delivery, diabetes, hypertension, vaginal bleeding, APH, placenta praevia, dental procedures, BMI, sex of the newborn |
| Aregawi et al., 2019 [27] | AOR (95% CI) | Rural residence (2.1, 1.1–4.2) | IPI < 24 months (5.4, 1.3–22.1), Previous PTB (3.7, 1.1–16.3), PROM (4.1, 1.9–8.9), induced labor (2.5, 1.1–5.9), multiple pregnancy (5.7, 2.3–14.3) | Malaria during pregnancy (4.7, 2.0–11.2), presence of a chronic illness (4.6, 1.8–11.3) | NR | NR | NR | NR |
| Asefa et al., 2020 [28] | AOR (95% CI) | Age ≥ 35 (3.0, 1.4–6.3) | NR | NR | NR | NR | NR | Residence, ANC visits, gravidity |
| Aseidu et al., 2019 [29] | AOR (95% CI) | NR | PROM (2.3, 1.0–5.5), ANC > 4 (0.2, 0.1–0.4) | Preeclampsia/eclampsia (3.4, 1.0–11.9) | NR | NR | NR | Parity, Number of ANC visits, APH before, multiple birth, Mode of delivery, (P)PROM labor, Gestational Diabetes Mellitus (GDM), PIH, Pre-eclampsia/eclampsia, Preterm history, Birth Interval, Previous mode of delivery |
| Bater et al., 2020 [30] | AOR (95% CI) | Residence (0.6, 0.5–0.8), age > 20 years (0.8, 0.6–0.9), single (1.4, 1.0–2.0), home delivery (1.3, 1.1–1.5) | IPI > 24 months (0.8, 0.6–0.9), ANC > 4 (0.6, 0.5–0.7) | NR | NR | NR | NR | Residence, being age, education, diet, IPI, ANC visits, household food insecurity, not taking deworming medication or iron tablets during pregnancy, and delivering at home |
| Berhane et al., 2019 [31] | AOR (95% CI) | Unmarried mothers (4.1, 1.2–14.1) | NR | NR | NR | NR | NR | Sex of the newborn, marital status, maternal education, socioeconomic index, gravidity, parity |
| Berhanie et al., 2019 [32] | AOR (95% CI) | NR | NR | NR | IPV (2.5, 2.2–2.9), Physical violence (5.3, 4.0–7.1) | NR | NR | IPV, sexual violence, physical violence, psychological violence, and controlling behaviors |
| Berhe et al., 2019 [33] | ARR (95% CI) | NR | NR | PIH (5.1, 3.4–8.0) | NR | NR | NR | Maternal age, wealth status, educational status, residence, gravidity, mode of delivery, anemia and maternal undernutrition |
| Berhe et al., 2019 [34] | AOR (95% CI) | Unmarried mothers (5.2, 1.8–15.1) | NR | NR | NR | MUAC < 11 cm (2.4, 1.2–4.9) | NR | Age, income, education, occupation, height, pregnancy status, diet, medical problems |
| Brabin et al., 2019 [35] | ARR (99% CI) | NR | Préconception iron supplementation (2.2, 1.4–3.6) | NR | NR | NR | NR | MUAC at baseline, bed net use, birth month |
| Brhane et al., 2019 [36] | AHR (95% CI) | NR | IPI < 24 months (6.9, 3.1–15.3), ANC < 4 (2.2, 1.0–4.9), pregnancy complication (3.2, 1.6–6.3) birth defect (8.0, 2.6–25.1) | NR | NR | NR | NR | Maternal residence, planned pregnancy, history of perinatal death and maternal hemoglobin level |
| Butali et al., 2016 [37] | AOR (95% CI) | Age > 35 years (1.4, 1.1–1.7) | PMTCT attendance (0.9, 0.6–1.3), PROM (4.03, 2.5–6.40), unbooked for ANC (2.15, 1.6–2.9) | Hypertension (2.8, 1.9–4.0) | NR | NR | NR | Maternal age, parity, fetal position, delivery method and booking status |
| Chen et al., 2012 [38] | AOR (95% CI) | NR | NR | HIV infection (1.3, 1.2–1.4) | NR | NR | Preconception HAART (1.2, 1.1–1.4) | NR |
| Chiabi et al., 2013 [39] | AOR (95% CI) | Student mother (0.4, 0.2–0.9), married (0.4, 0.19–0.8) | Multiple gestation (3.8, 2.6–5.4), congenital malformation (2.8, 1.2–6.2), ≥4 ANC visits (0.2, 0.1–0.4) | UTI (39.0, 17.2–88.6) | NR | NR | NR | Gender, age, occupation, education, marital status, residence, parity, gravidity, ANC visits, place of ANC visit |
| Conroy et al., 2017 [40] | AOR (95% CI) | NR | NR | NR | NR | NR | First trimester ART initiation (1.31, 1.03–1.68) | NR |
| Dadi et al., 2020 [41] | ARR (95% CI) | Muslim (1.61, 1.17–2.22), government employee (1.49, 1.00–2.19), have fear of delivery (1.46, 1.06–2.01) | No ANC uptake (1.77, 1.03–3.03) | NR | NR | NR | NR | MUAC, depressive symptoms, coping with stress |
| De Beaudrap et al., 2013 [42] | AOR (95% CI) | NR | NR | Malaria (1.9, 1.1– 3.5), HIV (2.33, 1.17–4.64 | NR | NR | NR | Maternal age, education level, residence, HIV status, number of clinic follow-up visits, newborn’s sex |
| Debelo et al., 2020 [43] | ARR (95% CI) | Age > 35 (2.7, 1.8–3.8) | NR | NR | NR | NR | NR | Number of alive child(ren), wealth quintile, husband occupational status, gravidity, husband educational status, maternal educational status, parity, ANC follow-up, previous adverse pregnancy outcomes, health insurance, place of residence |
| Deressa, 2018, Ethiopia [44] | AOR (95% CI) | NR | NR | PIH (0.182, 0.067–0.493), HIV (3.4, 1.048–11.1) | NR | NR | NR | NR |
| Ejigu et al., 2019 [45] | AOR (95% CI) | NR | NR | NR | NR | NR | Zidovudine monotherapy (0.4, 0.2–0.6) | Maternal age, weight, marital status, education, parity, CD4 cell count during pregnancy and WHO clinical stage during pregnancy |
| Elphinstone et al., 2019 [46] | ARR (95% CI) | NR | NR | Malaria positive before 24 weeks (1.7, 1.2–2.3) | NR | NR | NR | Treatment arm (ISTp versus IPTp), maternal age, gravidity, socioeconomic status, education status, body mass index (BMI), and hemoglobin at Visit 1 |
| Ezechi et al., 2012 [47] | AOR (95% CI) | NR | Multiple pregnancy (8.6, 6.7–12.9) | Presence of opportunistic infection (1.9, 1.1–5.7) | NR | NR | PI based regimen (5.4, 3.4–7.8) | Birth weight, stage of HIV disease, reproductive tract infection and medical disorders |
| Feresu et al., 2010 [48] | APR (95% CI) | Rural residence (1.2, 1.1–1.3) | Multiple gestation (4.2, 3.7–4.6), ANC < 1 visit (3.0, 2.8–3.3), nulliparity (0.90, 0.83–0.99) | NR | NR | NR | NR | Age, sex, residence antenatal care, delivery type and parity |
| Feresu et al., 2004 [49] | ARR (95% CI) | NR | History of abortion/stillbirth (1.5, 1.1–2.1), APH (3.1, 1.9–5.0), placental Previa (3.3, 1.3–8.1) | Eclampsia (3.6, 1.7–7.6), anemia (4.1, 1.8–9.4), Malaria (2.9, 1.7–5.0) | NR | MUAC < 28.6 cm (0.95, 0.92–0.99), | NR | Maternal age, antenatal care attendance, referral status, drinking home brew during pregnancy, and history of abortion or stillbirth |
| Gejo et al., 2021 [50] | AOR (95% CI) | Urban residence (0.5, 0.2–1.0) | No ANC (0.1, 0.0–0.7), PROM (3.8, 1.5–9.7), multiple pregnancies (5.5, 2.5–12.4) | PIH (3.8, 1.4–10.1) | NR | NR | NR | Parity, residency, history of abortion, history of PTB, history of stillbirth, UTI, diabetes mellitus, anemia, ANC follow up, labour, APH, PROM, PIH, polyhydramnios and multiple pregnancy |
| Gesase et al., 2018 [51] | AOR (95% CI) | NR | NR | Periodontal disease (2.3, 1.3–4.3) | NR | NR | NR | Age, parity, previous preterm birth, he same adverse fetal outcome, and pre-eclampsia |
| Gumede et al., 2017 [52] | AOR (95% CI) | NR | ANC < 1 visit (1.6, 1.4–1.8) | HIV infection (1.3, 1.2–1.4) | NR | NR | NR | HIV status, study site, infant sex |
| Habib et al., 2011 [53] | ARR (95% CI) | Unknown HIV status (1.4, 1.2–1.6) | HIV infection (1.8, 1.1–2.7) | NR | ||||
| Hassen et al., 2021 [54] | AOR (95% CI) | NR | Previous PTB (3.5, 1.4–8.8), IPI < 24 months (4.5, 2.0–10.2), history of obstetric complications (3.8, 1.6–9.0) | NR | NR | NR | NR | Monthly family income, history of PTB, IPI, ANC visit, mode of delivery in current pregnancy, experiencing obstetric complication in current pregnancy, maternal weight, infant birth weight, and presence of birth asphyxia |
| Hussain et al., 2011 [55] | AOR (95% CI) | NR | NR | HIV infection (1.4, 1.1–1.7) | NR | NR | NR | NR |
| Hussein et al., 2009 [56] | AOR (95% CI) | NR | NR | Mild anemia (1.4, 1.1–1.9), severe anemia (4.1, 2.5–6.6) | NR | NR | NR | NR |
| Hussein et al., 2020 [57] | ARR (95% CI) | Charcoal use (1.5, 1.1–2.1) | NR | NR | NR | NR | NR | Maternal malaria at birth, parity and number of cooking sessions a day |
| Iyoke et al., 2015 [58] | AOR (95% CI) | Unmarried mothers (2.4, 1.5–3.7) | ANC < 1 visit (2.6, 1.9–6.1), previous PTB (5.1, 2.7–9.1), pregnancy complication (5.1, 2.4–11.8), nulliparity (2.1, 1.2–4.9) | NR | NR | NR | NR | Educational status, occupation, PTB, parity, marital status and the presence of complicationsof pregnancy (antepartum hemorrhage, preeclampsia/eclampsia or PROM) |
| Johnson et al., 2016 [59] | ARR (95% CI) | NR | NR | Gestational hypertension (1.2, 1.1–14), chronic hypertension (2.3, 2.1–2.6), severe hypertension (4.4, 3.2–6.2) | NR | NR | NR | Maternal age, marital status, salaried employment, and booking weigh |
| Kalanda et al., 2006 [60] | AOR (95% CI) | NR | Primigravida (2.3, 1.3–4.0), <5 ANC visits (2.2, 1.3–3.7) | NR | NR | NR | NR | Maternal age, ANC visits, maternal height, MUACHb leval at recruitment, peripheral or placental and peripheral malaria, taking ferrous sulphate supplements and taking sulphadoxine–pyrimethamine |
| Kalengo et al., 2020 [61] | ARR (95% CI) | NR | Previous PTB (1.9, 1.5–2.3), IPI > 59 months (1.4, 1.0–1.9) | Preeclampsia (1.5, 1.1–2.0) | NR | NR | NR | Mother’s age, mother’s education, PROM and alcohol use |
| Kassa et al., 2019 [62] | AOR (95% CI) | Age < 20 (1.7, 1.1–2.5) | ANC ≥ 1 visit (0.4, 0.2–0.8) | Preeclampsia (2.6, 1.2–5.5) | NR | NR | NR | Maternal age, residence, school attendance, marital status, wealth status, educational status of the father and the mother, anemia, iron-folic acid supplementation during current pregnancy, ANC attendance, partner involvement in ANC, experience of at least one form of gender based violence (physical, sexual or psychological violence) during the current pregnancy, and preeclampsia |
| Kelkay et al., 2018 [63] | AOR (95% CI) | NR | History of abortion (2.3, 1.2–4.9) | Anemia (2.4, 1.1–5.2) | Cigarette/alcohol use (3.6, 1.6–8.2) | NR | NR | Parity, medication intake, smoking cigarette/drinking alcohol during the most recent pregnancy, history of abortion, hemoglobin level, a physical congenital defect in the most recent baby, and history of bearing low birth weight baby, history of still birth, history of PTB, malaria |
| Kongnyuy et al., 2008 [64] | AOR (95% CI) | Age < 20 (1.8, 1.2–2.5) | NR | NR | NR | NR | NR | Gravidity, antenatal visits, marital status, employment status and level of education |
| Koss et al., 2014 [65] | AOR (95% CI) | NR | NR | NR | NR | Weight gain < 0.1 Kg/week (2.4, 1.2–4.4) | NR | Adjustment for time since HIV diagnosis and ART regimen |
| Kumwenda et al., 2017 [66] | AOR (95% CI) | Age < 20 (2.6, 1.2–5.8) | NR | NR | NR | NR | NR | NR |
| Li et al., 2016 [67] | ARR (95% CI) | NR | NR | Hypertension (1.3, 1.1–1.5) | NR | NR | Preconception HAART use (1.2, 1.1–1.5) | CD4+ cell count, maternal nutritional status |
| Mahande et al., 2013 [68] | ARR (95% CI) | NR | Previous PTB (2.7, 2.1–3.4), previous perinatal death (2.6, 1.9–3.5), previous LBW (2.9, 2.3–3.6) | Previous preeclampsia (2.5, 1.7–3.7) | NR | NR | NR | Maternal age and maternal education |
| Mahande et al., 2016 [69] | AOR (95% CI) | NR | IPI < 24 months (1.5, 1.3–1.7), IPI ≥ 60 months (1.1, 1.02–1.2) | NR | NR | NR | NR | Maternal age, maternal marital status, maternal educational status, maternal occupation, parity, area of residence, number of antenatal care visits (ANC), use of family planning methods and use of alcohol during pregnancy |
| Mahande et al., 2016 [70] | AOR (95% CI) | NR | NR | Malaria (1.12, 1.01–1·26), amebiasis (1.8, 1.1–2.9) | NR | NR | NR | Maternal age, parity, antenatal care visits maternal education, maternal occupation, area of residence, marital status |
| Mahapula et al., 2016 [71] | AOR (95% CI) | NR | No ANC (5.1, 1.4–17.8), vaginal discharge (5.2, 1.1–24.4), public perinatal care (2.1, 1.1–4.1), multiple pregnancy (8.6, 4.5–16.5), complications (2.7, 1.3–5.3), cervical incompetency (11.6, 1.1–121·5), polyhydramnios (8.3, 1.7–40.2) | Untreated UTI (2.7, 1.2–6.1) | NR | NR | NR | NR |
| Malaba et al., 2017 [72] | AOR (95% CI) | NR | NR | HIV infection (1.9, 1.3–2.8) | NR | NR | NR | Age, parity, BMI and previous PTB |
| Malaba et al., 2020 [73] | ARR (95% CI) | NR | NR | PIH (1.5, 1.1–2.0) | NR | NR | NR | Age, parity, BMI and previous PTB |
| Mboya et al., 2021 [74] | AOR (95% CI) | NR | Referred for delivery (1.3, 1.1–1.5), <4 ANC visits (5.6, 4.7–6.8), PROM (1.6, 1.1–2.5), placental Previa (8.1, 3.6–18.1) | Preeclampsia/eclampsia (1.6, 1.3–2.0), | NR | NR | NR | Maternal age, level of education, referral status, pre-eclampsia/eclampsia, number of ANC visits, parity, PROM, abruption placenta, placenta previa, delivery mode, child’s birth weight, perinatal status and year of birth. |
| Mehari et al., 2020 [75] | AOR (95% CI) | Age ≥ 35 years (3.6, 1.5–8.9) | NR | NR | NR | NR | NR | Residence, number of ANC visits, malpresentation, gravidity, bad obstetric history, Pregnancy Induced Hypertension, APH, PROM and Amniotic Fluids disorders |
| Mekonen et al., 2019 [76] | AOR (95% CI) | NR | Obstetric complications (6.6, 3.4–12.6), <4 ANC visits (5.1, 1.7–15.4), PROM (3.0, 1.5–6.2) | Anemia (2.9, 1.3–6.6) | NR | MUAC < 24 cm (2.6, 1.1–6.1) | NR | NR |
| Mekuriyaw et al., 2020 [77] | AOR (95% CI) | No education (2.2, 1.3–3.9) | PROM (6.4, 3.2–12.8), multiple pregnancy (4.1, 1.7–9.8), previous abortion (2.9, 1.3–6.4) | Anemia (2.8, 1.1–7.3), PIH (4.7, 2.5–9.0), | NR | NR | NR | NR |
| Mochache et al., 2018 [78] | ARR (95% CI) | NR | NR | Depression (3.6, 1.7–7.5) | NR | NR | NR | NR |
| Mombo-Ngoma et al., 2016 [11] | AOR (95% CI) | Age ≤ 16 years (2.16, 1.10–4.24) | NR | NR | NR | NR | NR | Country, first antenatal clinic visit, treatment group and infant sex |
| Moodley et al., 2017 [79] | AOR (95% CI) | Age ≥ 35 years (0.4 (0.2–0·90) | NR | NR | NR | NR | NR | Age, gravidity, socioeconomic status, HIV infection, chlamydia, trichomonas, gonorrhea |
| Muhihi et al., 2016 [80] | ARR (95% CI) | Age < 20 years (1.2, 1.1–1.4) | Nulliparity (1.2, 1.1–1.3) | NR | NR | Mothers’ height < 150 cm (1.3, 1.1–1.7) | NR | NR |
| Muhumed, 2021, Ethiopia [81] | AOR (95% CI) | Rural residence (4.5, 1.4–14.4) | History of abortion (5.0, 1.9–13.5) | Hypertension (3.2, 1.1–10.2) | NR | NR | NR | NR |
| N’Dao et al., 2006 [82] | AOR (95% OR) | NR | NR | Placental malaria (3.5, 1.8–6.7) | NR | NR | NR | NR |
| Ngandu et al., 2021 [83] | AOR (95% CI) | Secondary level education (2·21, 1.07–4.59), South African (3.72 (1.51–9.15) | Duration between first prenatal visit and delivery (0.72, 0.68–0.77), vaginal delivery (1.97, 1.22–3.15), GA determined at first prenatal visit (0.93, 0.89–0.98), | NR | NR | Weight at delivery (0.99, 0.97–1.00), gestational weight gain per week (0.21, 0.07–0.61) | NR | Newborn and maternal characteristics, and country |
| Noble et al., 2005 [84] | AOR (95% CI) | NR | NR | Tuberculosis (10.2, 1.2–89.9), Malaria (2.4, 1.1–5.3) | NR | NR | NR | Maternal age, gravidity, education, marital status, pre-pregnancy body mass index, and maternal use of and iron supplements during the current pregnancy |
| Oluwole et al., 2020 [85] | AOR (95% CI) | NR | NR | Vitamin D serum level < 30 ng/mL (9.4, 2.4–36.5) | NR | NR | NR | Age, level of education, religion, booking status, alcohol intake, smoking of tobacco, and skin color |
| Olusanya et al., 2010 [86] | AOR (95% CI) | Unmarried (1.7, 1.1–2.7), shared sanitation (1.3, 1.1–1.5), small trading (1.5, 1.3–1.9), fulltime job (1.3, 1.1–1.6) | PROM (3.6, 2.0–6.5), APH (3.5, 2.0–6.4), No history of CS (1.4, 1.1–1.9), No ANC (1.3, 1.1–1.5) | Hypertension (2.2, 1.7–2.9), Maternal disease (1.5, 1.1–2.1), | NR | NR | NR | Maternal and infant perinatal factors |
| Omokhodion et al., 2010 [12] | AOR (95% CI) | Exposure to vibration at work (2.40, 1.21–4.77) | Nulliparity (2.24, 1.26–3.97), history of PTB (6.45, 1.41–29.53), ≤ 4 ANC visits (4.05, 1.70–9.66), prolonged PROM (6.41, 1.86–22.11) | NR | NR | NR | NR | Age, marital status, matenal education, type of residence, cooking with kerosense, parity, history of PTB, prolonged PROM, hospital admission during preganancy, ANC visits, hypertension |
| Osman et al., 2001 [87] | AOR (95% CI) | NR | NR | NR | NR | Weight < 49 Kg (3.0, 1.7–5.2), Weight gain < 1 Kg (2.8, 1.6–5.0) | NR | Number of children alive |
| Padonou et al., 2014 [88] | AOR (95% CI) | NR | NR | NR | NR | NR | NR | Parity, maternal anaemia, presence of placental malaria, infections |
| Parek et al., 2011 [89] | AOR (95% CI) | NR | NR | HIV infection (1.7, 1.3–2.2), Hypertension (1.8, 1.2–2.6) | NR | NR | NR | Maternal age, marital status, employment status, time of Initiation of prenatal care |
| Regasa et al., 2021 [90] | AOR (95% CI) | NR | No ANC (3.2, 1.4–7.4), 1–2 ANC visits (2.3, 1.2–4.4), Previous PTB (5.2, 2.3–20.9), IPI < 24 months (4.4, 2.1–9.5), obstetric complication (2.5, 1.3–4.7) | Reproductive tract infection (2.5, 1.0–6.3) | NR | NR | NR | History of abortion, male sex, lack of ANC follow up, iron supplementation, anxiety during pregnancy |
| Rugumisa et al., 2020 [91] | AOR (95% CI) | NR | Previous PTB (13.2, 1.7–102.0), placenta Previa (12.6, 1.6–98.0), PROM (8.8, 1.3–46.0) | NR | NR | NR | NR | NR |
| Shava et al., 2019 [92] | AOR (95% CI) | HIV and Syphilis coinfections (1.5, 1.1–2.1) | Maternal age, marital status, occupation, education, parity, low maternal haemoglobin | |||||
| Siakwa et al., 2020 [93] | AOR (95% CI) | Age 20–34 (1.6, 1.4–2.6) | NR | NR | NR | NR | NR | NR |
| Sigalla et al., 2017 [94] | AOR (95% CI) | NR | Previous miscarriage (2.2, 1.1–4.1) | NR | Physical violence (2.9, 1.3–6.5) | NR | NR | Previous PTB, women’s age, education level, occupation, and alcohol consumption, previous LBW |
| Sullivan et al., 1999 [95] | AOR (95% CI) | Delivery in rainy season (3.9, 1.8–8.8), no education (3.5, 1.6–7.8) | NR | Malaria (3.3, 1.3–8.8) | NR | NR | NR | Placental parasitemia, maternal peripheral parasitemia- delivery, ANC visits, placental weight |
| Tadese et al., 2020 [96] | AOR (95% CI) | NR | NR | NR | IPV (2.9, 1.4–6.2), Physical IPV (2.6, 1.3–6.8), emotional IPV (3.1, 1.4–6.9) | NR | NR | Residence, education level, maternal age, ANC visits, previous history of adverse birth outcomes, current maternal and husband substance use during pregnancy, medical problems during pregnancy, any other IPV |
| Teklay et al., 2018 [97] | AOR (95% CI) | NR | <4 ANC visits (2.2, 1.2–3.9), multiple pregnancy (2.5, 1.1–5.3), fetal distress (4.0, 1.9–8.2), birth defect (3.2, 1.2–83) | Hypertension (3.2, 1.6–6.7) | NR | NR | NR | Maternal height, PROM |
| Tembo et al., 2020 [98] | AOR (95% CI) | Age < 20 (1.4, 1.1–1.8) | NR | NR | NR | NR | NR | NR |
| Ticconi et al., 2003 [99] | AOR (95% CI) | NR | NR | HIV infection (4.1, 2.1–7.8), malaria (25.5, 12.2–52.9) | NR | NR | HIV treatment (9.1, 4.0–20.8), Malaria treatment (23.2, 11.4–47.2) | Age, parity, malaria, malaria treatment, HIV treatment |
| Uwambaye et al., 2021 [100] | AOR (95% CI) | NR | NR | Periodontitis (6.4, 3.9–10.4) | NR | NR | NR | Employment status, tobacco use, history of Malaria, History of UTI, History of stress during pregnancy, other causes of stress |
| Van Den Broek et al., 2014 [101] | AOR (95% CI) | NR | Previous PTB (2.1, 1.2–3.80) | NR | NR | BMI > 18·5 (0.91, 0.85–0.97), Weight gain (0.89, 0.82–0.97) · | NR | |
| Van der Merwe et al., 2011 [102] | AOR (95% CI) | NR | NR | NR | NR | NR | HAART exposure < 28 weeks; PI-based (3.0, 1.1–8.4), NVP-based (5.4, 2.1–13.7), EFV-based (5.6, 2.1–15.2) | Age, anaemia, malaria, BMI, previous neonataL death or stillbirth |
| Wagura et al., 2018 [103] | AOR (95% CI) | NR | APH (4.3, 1.5–12.0), Prolonged PROM (5.3, 2.3–12.2) | PIH (7.8, 3.7–16.5) | NR | NR | NR | Maternal age, parity, twin gestation, UTI, previous preterm birth |
| Wakeyo et al., 2020 [104] | AOR (95% CI) | Secondary education and above (0.1, 0.1–0.7), | ANC (0.4, 0.2–0.9), history of abortion (2.3, 1.1–5.0), Previous PTB (5.0, 1.6–15.0) | UTI (3.6, 1.1–11.0) | NR | NR | NR | HIV status, employment status |
| Watson-Jones et al., 2007 [105] | AOR (95% CI) | NR | NR | Malaria (3.2, 1.9–5.2), Treated Bacterial Vaginosis (0.9, 0.6–1.4), untreated Bacterial Vaginosis (3.0, 1.3–6.6) | NR | NR | NR | Age, occupation, gravidity, bacterial vaginosis during pregnancy, HIV at delivery and maternal malaria |
| Woday et al., 2019 [106] | AOR (95% CI) | Age < 24 years (3.5, 1.1–10.8), rural residence (3.0, 1.2–7.5), No education (4.6, 1.1–8.6) | IPI < 24 months (2.5, 1.1–5.8), No ANC (10.8, 4.4–26.3), Previous adverse birth outcomes (3.5, 1.5–8.0) | Medical problems in pregnancy (13.9, 4.4–24.23) | NR | NR | NR | MUAC, HTN status in pregnancy, Alcohol consumption in pregnancy |
| Young et al., 2012 [107] | AOR (95% CI) | NR | NR | NR | NR | Gestational weight gain < 0·1 kg/week (3.5, 1.2–10.1) | NR | Birth spacing < 2 years, Baseline CD4 count, Maternal weight at 7 months gestation, socioeconomic status |
| Zar 2020 et al., [108] | Adjusted B (95% CI) | Mothers who were food insecure (−0.542), moderate-high (0.543) or high (0.605) socioeconomic status | Primigravida (0.481) | PIH (−1.226), preeclampsia or eclampsia (1.741), gestational diabetes (−2.837), anemia (0.420) | NR | Higher BMI (0·078) | NR | Substance abuse, mental health and psychosocial factors, HIV infection, maternal age, ANC clinic attended, marital status |
| Zash et al., 2018 [109] | ARR (95% CI) | NR | NR | NR | NR | NR | Preconception ART (1.3, 1.1–1.7) | NR |
| Zewde et al., 2020 [110] | AOR (95% CI) | NR | Previous PTB (2.6, 1.3–5.2) | NR | NR | NR | NR | ANC visits, history of APH, hemoglobin levels, birth interval less than 24 months, history of chronic disease |
ANC—Antenatal Care, APH—Antepartum Haemorrhage AHR—Adjusted Hazard Ratio, AOR—Adjusted Odds Ratio, ARR—Adjusted Risk Ratio, ART—Antiretroviral Therapy, BMI—Body Mass Index, BW—Birthweight, CFR—Case Fatality Rate, CS—Caesarean Section, EFV—Efavirenz, HAART—Highly Active Antiretroviral Therapy, IPI—Inter Pregnancy Interval, IPT—Intermittent Malaria Preventive Therapy, IPV—Intimate Partner Violence, LMP—Last Menstrual Period, LBW—Low Birthweight, MUAC—Mid-Upper Arm Circumference, NA—Not Applicable, NDD—Neurodevelopmental Delay, NR—Not Reported, NVP—Nevirapine, PIH—Pregnancy-induced Hypertension, PMTCT—Prevention of Mother To Child Transmission, PTB—Preterm Births, PROM—Premature Rapture of Membranes, RCT—Randomised Control Trial, SFH-Symphysis—Fundal Height, USS—Ultrasonography/Ultrasound, UTI—Urinary Tract Infection.