Effect of Zinc and Phenylalanine Supplementation on Birth Outcomes: A Systematic Review and Meta-Analysis

Abstract

Enhancing antenatal and birth outcomes is a global concern for midwives. This systematic review examined the effects of zinc and phenylalanine supplementation on antenatal and birth outcomes among healthy pregnant women. A systematically developed search strategy was employed to identify relevant studies published between 2004 and 2024, focusing on clinical trials conducted in English. Inclusion criteria encompassed studies involving healthy pregnant women receiving zinc and/or phenylalanine supplementation, with outcome variables including foetal death, preterm birth, birth weight, and low birth weight. A total of seven randomized controlled trials met the inclusion criteria and were included in the analysis. The results revealed that antenatal zinc supplementation did not significantly reduce the risk of foetal death (RR: 1.12, 95% CI: 0.84-1.50, p = 0.44), preterm birth (RR: 1.00, 95% CI: 0.66-1.52, p = 0.99), and low birth weight (RR: 1.09, 95% CI: 0.83-1.42, p = 0.54).  There was no difference in birth weight of newborns between the groups (Mean difference: -0.03, 95% CI: -0.07-0.00, p = 0.06). There was a paucity of studies on antenatal phenylalanine supplementation. The findings underscore the complexity of the relationship between zinc supplementation and antenatal outcomes. Future studies should explore the impact of phenylalanine supplementation with and without zinc on birth outcomes to provide a more comprehensive understanding of the role of the nutrients in antenatal care.