Relationship between serum zinc levels and preeclampsia in pregnant women at the University Teaching Hospital, Lusaka, Zambia

Abstract

Preeclampsia is one of the leading causes of maternal mortality and pre-term delivery around the world. Though its exact cause is not yet known, it is found more commonly in developing countries. Deficiency of serum Zinc has been implicated in the pathophysiology of preeclampsia due to its crucial role as a cofactor of antioxidant enzymes as oxidative stress is a hallmark of preeclampsia. Reports from various regions of the world are controversial and largely inconclusive. In Zambia, the relationship between serum Zinc levels and preeclampsia remains unexplored yet Zambia lies within the geographical region thought to be most deficient in Zinc. The purpose of the study was to investigate the association between serum Zinc levels and preeclampsia in pregnant women at University Teaching Hospital, Lusaka, Zambia. A comparative cross-sectional study design was employed on purposively sampled 41 preeclamptic and 57 non-preeclamptic pregnant women over a four month period from February 2016 to May 2016 at the maternity clinic of the University Teaching Hospital. Systolic blood pressure > 140 mm Hg and/ or diastolic blood pressure > 90 mm Hg with proteinuria atleast 1+ defined a preeclamptic case. Control participants comprised healthy pregnant women who were attending antenatal services. An interview guide was used to collect data on social demographics. Serum samples from participants were analysed for Zinc concentration by Atomic Absorption Spectrophotometry. Data was analysed using Student T-test and entered in Stata version 14. Maternal age was identified as a risk factor of preeclampsia in that there was significantly greater proportion of preeclamptic women aged between 30 and 40 years (61%; p = 0.006) than that of preeclamptic women aged between 18 to 30 years of age (32%; p = 0.018). However, there was no significant difference in the mean serum Zinc levels of the preeclamptic (89.17 ± 47.19 μg/dL) versus the non-preeclamptic pregnant women (76.20 ± 35.23 μg/dL) (p = 0.122). The data also showed that maternal age group, gestational age, family history of preeclampsia, and residential area density had no significant effect on the relationship p between serum Zinc level and preeclampsia (p values > 0.05). No correlation was found between blood pressure and serum Zinc levels in the total sample (SBP: r = 0.149, p = 0.2599; DBP: r = 0.1656, p = 0.1031) or in the preeclamptic cases alone (SBP: r = -0.0636, p = 0.6928; DBP: r = 0.0452, p = 0.7788). Our results implied lack of a direct relationship between serum Zinc level and preeclampsia in the pregnant women at UTH. Incidentally, maternal age was found to be a risk factor for preeclampsia. Serum Zinc is of doubtful clinical value in preeclampsia. Nonetheless, further investigation in the role of serum Zinc and other minerals/ metabolites in preeclampsia is merited as they may act as early predictors of the condition. Key words: preeclampsia, Zinc level, pregnant women, University Teaching Hospital