Table 1.
Included studies assessing maternal zinc status and birthweight.
| Author, Country | Sample Size | Zinc Measure | Outcome of the Study |
|---|---|---|---|
| (1) Sample Type | |||
| (2) Time at Which Gestation Diet Was Assessed or Sample Collected | |||
| (3) Method of Analysis | |||
| [42] Simmer, United Kingdom a | 28 SGA 29 uncomplicated |
Dietary zinc intake Third trimester of pregnancy 7 day dietary recall |
↓ mean (SEM) dietary intake in the SGA mothers compared to the women with uncomplicated pregnancies. SGA: 11.3 (0.5) vs. uncomplicated: 13.0 (0.6) mg/day, p < 0.05 |
| [43] Negandhi, India b | 144 LBW 240 uncomplicated |
Dietary zinc intake 26–30 weeks 24 h dietary recall |
↓ mean dietary zinc intake in women with a LBW infant compared to those with an uncomplicated pregnancy. LBW: 5.39 mg/day vs. uncomplicated 6.77 mg/day, p < 0.001 |
| [44] Scholl, United States c | 115 with zinc intake ≤6 mg/day 699 with zinc intake ˃6 mg/day |
Dietary zinc intake 28 and 36 weeks 24 h dietary recall |
2-fold ↓ risk of delivering a LBW infant with dietary zinc intake ˃6 mg/day. OR: 2.01, 95% CI: 1.11–3.66 |
| [45] Neggers, United States d | 180 LBW 1218 uncomplicated |
Dietary zinc intake 18 and 30 weeks 24 h dietary recall using the nutrient data base developed by the University of Minnesota |
NS association between low dietary zinc intake (less than median) and risk of LBW. OR: 1.4, 95% CI: 0.9–2.1 |
| Inadequate dietary zinc intake estimated to affect <17% of the studied population | |||
| [46] Wang, China b | 247 with serum zinc <560 µg/L 2940 with serum zinc ≥560 µg/L |
Fasting serum zinc Across gestation Flame AAS |
↑ incidence of LBW in the mothers with serum zinc <560 µg/L compared to those with serum zinc ≥560 µg/L. Adjusted RR: 3.41, 95% CI: 1.97, 5.91 |
| [47] Voss Jepsen, Denmark a | 10 SGA 30 uncomplicated |
Heparin plasma zinc Collected at 35–41 weeks AAS |
↑ mean (SD) plasma zinc between SGA mothers and those with uncomplicated pregnancies. SGA: 732 (85) vs. uncomplicated: 654 (78) μg/L, p = 0.03 |
| [48] Borella, Italy a | 16 SGA 35 uncomplicated |
Heparin plasma zinc Collected in the third trimester Flame AAS |
↑ mean (SD) plasma zinc in SGA women compared to women with uncomplicated pregnancies. SGA: 685.6 (119.6) vs. uncomplicated: 627.5 (150) µg/L, p < 0.001 |
| [49] Neggers, USA e | 39 LBW 437 uncomplicated |
Serum zinc Collected across gestation Flame AAS |
8-fold ↑ prevalence of LBW with serum zinc in the lowest quartile (457.5–797.4 µg/L) compared to the highest (1039.2–1660.1 µg/L). OR: 8.2, 95% CI:2.4–27.5 |
| [50] Bro, Denmark a | 47 SGA and 34 preterm 220 uncomplicated |
Serum zinc Collected at delivery Flame AAS |
NS mean (SD) serum zinc levels between SGA and women with uncomplicated pregnancies. SGA: 764.7 (119.6) vs. uncomplicated: 679.7 (98) µg/L |
| [38] Hyvonen-Dabek, Finland f | 4 SGA 10 uncomplicated |
Serum zinc Collection time not specified Particle induced X-ray emission |
NS mean (SD) serum zinc in SGA women compared to those with uncomplicated pregnancies. SGA: 1270 (320) vs. uncomplicated: 1150 (220) µg/L |
| [51] Mistry, UK a* | 19 SGA 107 uncomplicated |
Heparin plasma zinc Collected at 28–32 weeks Inductively coupled plasma mass spectrometry |
NS in mean (95% CI) plasma zinc between SGA women and those with uncomplicated pregnancies. SGA: 708.1 (510.4–905.8) vs. uncomplicated: 634.4 (580.5–688.2) μg/L |
| [52] Tamura, USA g | 80 SGA 80 uncomplicated |
Serum zinc Collected at 18 weeks and 30 weeks Flame AAS |
NS in mean (SD) plasma zinc between SGA and women with uncomplicated pregnancies at 18 weeks. SGA: 627 (118) vs. uncomplicated: 667 (98) µg/L NS in mean (SD) plasma zinc between SGA and women with uncomplicated pregnancies at 30 weeks. SGA: 562 (92) vs. uncomplicated: 575 (92) µg/L |
| [53] Tamura, USA a | 139 SGA 2038 uncomplicated |
Non-fasting heparin plasma zinc Collected at first prenatal visit (6 to 34 weeks) Flame AAS |
NS in the prevalence (n (%)) of SGA measured between the lowest quartile and upper 3 quartiles of zinc. Highest: 103 (4.4) vs. lowest: 36 (4.8) |
| [54] Ghosh, China a | 22 SGA 38 uncomplicated |
Serum zinc Collected within 24 h of delivery AAS |
NS in mean (SD) serum zinc levels between SGA and women with uncomplicated pregnancies. SGA: 508.1 (185.9) vs. uncomplicated: 542.3 (162.8) μg/L |
| [55] Cherry, USA b | 29 LBW 230 uncomplicated |
Heparin plasma zinc Collected across gestation AAS |
NS mean (SEM) plasma zinc in mothers with a LBW infant compared to mothers with uncomplicated pregnancies. LBW: 604.9 (22.4) vs. uncomplicated: 577.2 (7.7) μg/L |
| [56] Bogden, USA h | 22 LBW 50 uncomplicated |
EDTA plasma zinc Collected at delivery Flame AAS |
NS mean (SEM) plasma zinc in women with a LBW infant compared to women with uncomplicated pregnancies. LBW: 640 (20) vs. uncomplicated: 620 (20) µg/L |
| Inadequate dietary zinc intake estimated to affect ≥17% of the studied population | |||
| [57] Atinmo, Nigeria h | 20 LBW 30 uncomplicated |
Heparin plasma zinc Collected at delivery AAS |
↓ mean (SD) serum zinc in women with a LBW infant compared to those with uncomplicated pregnancies. LBW: 663.1 (144.6) vs. uncomplicated: 731.5 (235.6) µg/L, p < 0.05 |
| [58] Abass, Sudan b | 50 LBW 50 uncomplicated |
Serum zinc AAS Atomic absorption spectrometry |
↓ median (IQR) serum zinc in women with a LBW infant compared to those with uncomplicated pregnancies. LBW: 629 (363–968) vs. uncomplicated 962 (846–1257) µg/L, p < 0.001 |
| [59] Rwebembera, Tanzania c | 81 LBW 84 uncomplicated |
EDTA plasma zinc Collected at delivery Flame AAS |
3-fold ↓ risk of delivering a LBW infant with serum zinc ≥ 392.2 µg/L OR: 3.07, 95% CI: 1.07–8.97 |
| [60] Bahl, India c | 19 LBW 56 uncomplicated |
Serum zinc Collected at delivery Flame AAS |
↓ mean (SD) serum zinc in women with a LBW infant compared to those with uncomplicated pregnancies. LBW: 553 (43) vs. 692 (95) µg/L, p < 0.001 |
| [61] Singh, India e | 47 LBW 45 uncomplicated |
Serum zinc Collected at delivery AAS |
↓ mean (SD) serum zinc in women with a LBW infant compared to those with uncomplicated pregnancies. LBW: 623 (330) vs. uncomplicated: 895 (514) μg/L, p < 0.001 |
| [62] Prema, India e | 23 LBW 208 uncomplicated |
Serum zinc Collected at delivery between 9–11.30 a.m. Flame AAS |
↑ mean (SD) serum zinc in mothers with a LBW infant compared to mothers with an uncomplicated pregnancy. LBW: 660 (162) vs. uncomplicated: 620 (146) µg/L, p < 0.01 |
| [63] Badakhsh, Iran b | 30 LBW 110 uncomplicated |
Serum zinc Collected at delivery AAS |
↑ mean (SD) serum zinc in mothers with a LBW infant compared to mothers with an uncomplicated pregnancy. LBW: 686.2 (204.8) vs. uncomplicated: 514.3 (138.8) µg/L, p < 0.001 |
| [64] Goel, India a | 20 LBW 25 uncomplicated |
Heparin plasma zinc Collected at delivery AAS |
NS mean (SD) plasma zinc in women with a LBW infant compared to those with an uncomplicated pregnancy. LBW: 726 (61) vs. uncomplicated: 763 (56) μg/L |
| [65] Srivastava, India b | 26 LBW 25 uncomplicated |
Heparin plasma zinc Collected at delivery Flame AAS |
NS mean (SD) plasma zinc between mothers with a LBW infant and mothers with uncomplicated pregnancies. LBW: 6470 (4860) vs. uncomplicated: 5670 (2490) µg/L |
| [66] Jeswani, India a | 10 SGA 25 uncomplicated |
Serum zinc Collected at 28–40 weeks AAS |
NS mean (SD) serum zinc in SGA women compared to those with uncomplicated pregnancies. SGA: 938 (76.2) vs. uncomplicated: 962.8 (194.8) µg/L |
| [67] George, India a | 65 SGA 51 uncomplicated |
Heparin plasma zinc Collected before labor between 8–10 a.m. AAS |
NS in mean (SD) plasma zinc between SGA and women with uncomplicated pregnancies. SGA: 675 (90) vs. uncomplicated: 706.7 (139) µg/L |
| [68] Akman, Turkey f | 22 SGA 34 uncomplicated |
Serum zinc Collected at delivery AAS |
NS mean (SD) serum zinc between SGA women and women with uncomplicated pregnancies. SGA: 1218 (543) vs. uncomplicated 1038 (343) µg/L |
| [69] Ozdemir, Turkey b | 16 LBW 59 uncomplicated |
Serum zinc Collected at 38–42 weeks Flame AAS |
NS mean (SD) serum zinc between mothers with a LBW infant and mothers with uncomplicated pregnancies. Data represented on graphs |
a SGA defined as ˂10th percentile; b LBW defined as ˂2500 g; c LBW defined as ≤2000 g; d LBW defined as ˂2750 g; e LBW defined as ˂2000; f SGA not defined; a* SGA defined as ˂10th percentile based on customised centiles; g SGA defined as ˂15th percentile; h LBW defined as ≤2500 g. Bold print signifies results that were significantly different. Abbreviations: AAS: atomic absorption spectrometry; CI: confidence interval; IQR: interquartile range; LBW: low birth weight; NS: non-significant; OR: odds ratio; SD: standard deviation; SEM: standard error of the mean; SGA: small for gestational age.