Researchers conducted a secondary analysis on the Women First Preconception Maternal Nutrition Trial and found high rates of maternal hypozincaemia despite daily zinc supplementation for the Indian cohort.
“Despite daily zinc supplementation for at least seven months or more, high rates of maternal hypozincaemia were observed. The association of hypozincaemia with impaired foetal growth suggests widespread zinc deficiency in these settings,” wrote the researchers in The Journal of Nutrition.
Data from foetal development at various stages of gestation up till the point of birth were also analysed. Researchers also studied their length- and weight-for-age Z scores, which refer to a newborn's length and weight in comparison to the mean measurements for their age.
“Maternal hypozincaemia at 34-weeks was associated with lower birth length-for-age Z-scores and weight-for-age Z-scores,” said the researchers.
In human pregnancy, adverse outcomes due to zinc deficiency have been harder to document. Furthermore, data regarding effects of small quantity-lipid-based nutrient supplements (SQ-LNS) on maternal serum zinc concentrations (SZC) in pregnancy and lactation are limited. Researchers therefore wanted to evaluate the effectiveness of zinc supplementation among women in low resource settings, and to assess the links with birth anthropometry (measurements that include weight, length and head circumference).
Researchers analysed data from three different sites – Guatemala, India and Pakistan – of the Women First Preconception Nutrition Trial.
The women were randomised into three arms, with approximately 100 participants in each arm. Arm 1 was the preconception group, Arm 2 the early pregnancy group, and Arm 3 the control group.
Arm 1 took 15 mg zinc of SQ-LNS daily from three months or more prior to conception; Arm 2 took the same SQ-LNS from around 12 weeks gestation through delivery, and Arm 3 did not take any SQ-LNS at all.
The researchers compared SZC at 12 weeks gestation, 34 weeks gestation, and three months postpartum. For this analysis, the proposed cut-off value for defining hypozincaemia was an SZC of below 66 μg/dL.
Birth anthropometry was also examined for newborns, who also had their gestational ages determined via ultrasound at various stages of pregnancy. Data analyses were performed separately for each stage of development.
There were three significant findings.
First, the association of hypozincaemia at 34-weeks with lower birth size contrasts with systematic reviews, which have generally found reduced rates of preterm delivery associated with zinc supplementation but without detectable benefit on foetal growth. Although hypozincaemia was not associated with preterm delivery in this study, as a secondary outcome, the sample size and rates of prematurity were likely too small to detect such a relationship.
Second, maternal SZC at 34 weeks of gestation were significantly higher for the preconception and pregnancy groups (Arms 1 and 2, respectively) compared to the control Arm 3. Since this result was observed at 34-weeks and not in early gestation, it may be related to the greater demand for zinc at a time of rapid foetal growth. Even with enhanced zinc absorption in the third trimester, however, these results show that the supplementation is insufficient to compensate for chronic marginally low dietary zinc intakes observed in the participants.
Third, a substantial prevalence of hypozincaemia was evident throughout the study despite women in the preconception group receiving SQ-LNS daily for at least 6 months and an average of around 12 months prior to the collection of biospecimen samples at 12 weeks. During pregnancy, the rate of hypozincaemia exceeded 20% in Pakistan in both early and late pregnancy and were more than 20% for India and Guatemala at 12-weeks and approached 50% by 34 weeks. The researchers’ observations were consistent with a dose-response meta-analysis that found only a modest association of zinc intake with SZC during pregnancy.
The rates of hypozincaemia observed in late pregnancy in the Women First participants in India and Pakistan (48% and 74%, respectively) are similar to or higher than indicated by limited data in existing literature.
Additionally, data from a randomised zinc supplementation trial conducted in healthy fully lactating women in Colorado indicated that the averages for both placebo and 15-mg/day zinc supplementation groups exceeded 80 μg/dL by 3 months postpartum.
The findings suggest that the prevalence of zinc deficiency was high among the Women First trial participants, and optimal intake of zinc over the course of a reproductive cycle in similar low resource settings is yet to be determined.
“Overall, the high rates of hypozincaemia observed in the participants through pregnancy and early lactation; the association of hypozincaemia with birth anthropometry; and the epidemiologic evidence of wide-spread zinc deficiency in women of reproductive age in similar low- and middle-income settings, support a conclusion that the risk of zinc deficiency was high in the WF (Women First) participants. In these contexts, the amount of zinc provided may have been insufficient,” concluded the researchers.
This signals a need for public health intervention to increase zinc intake among the affected populations, especially for pregnant and lactating women, to mitigate the risks of impaired foetal growth.
Source: The Journal of Nutrition
DOI: https://doi.org/10.1016/j.tjnut.2024.04.018
“Zinc supplementation initiated prior to or during pregnancy modestly impacted maternal status and high prevalence of hypozincemia in pregnancy and lactation: the Women First Preconception Maternal Nutrition Trial”
Authors: Jennifer F. Kemp 1, K Michael Hambidge et al.
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