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Undernutrition and malaria in pregnancy a dangerous dyad?

Holger W. Unger1,2, Per Ashorn3,4,5, Jordan E. Cates6, Kathryn G. Dewey7 and Stephen J. Rogerson1*
Background: In low-resource settings, malaria and macronutrient undernutrition are major health
problems in pregnancy, contributing significantly to adverse pregnancy outcomes such as preterm birth
and fetal growth restriction. Affected pregnancies may result in stillbirth and neonatal death, and
surviving children are at risk of poor growth and infection in infancy, and of non-communicable diseases
in adulthood. Populations exposed to macronutrient undernutrition frequently reside in malaria-endemic
areas, and seasonal peaks of low food supply and malaria transmission tend to coincide. Despite these
geographic and temporal overlaps, integrated approaches to these twin challenges are infrequent.
Discussion: This opinion article examines the current evidence for malaria-macronutrition interactions
and discusses possible mechanisms whereby macronutrient undernutrition and malaria may interact to
worsen pregnancy outcomes. Macronutrient undernutrition dysregulates the immune response. In
pregnant women, undernutrition may worsen the already increased susceptibility to malarial infection and
could impair development of protective immunity to malaria, and is likely to exacerbate the impact of
placental malaria on fetal growth. Malarial infection, in turn, can drive nutritional depletion; poor
gestational weight gain and weight loss in pregnancy increases the risk of adverse pregnancy outcomes.
Despite a commendable number of studies and trials that, in isolation, attempt to address the challenges of
malaria and undernutrition in pregnancy, few dare to venture beyond the single disease single solution
paradigm. We believe that this may be a lost opportunity: researching malarianutrition interactions, and
designing and implementing integrated interventions to prevent and treat these commonly co-existing and
intertwining conditions, may markedly reduce the high burden of preterm birth and fetal growth
restriction in affected areas.
Conclusion: We call for more collaboration between researchers studying malaria and nutrition in
pregnancy, and propose a research agenda to address this important twin health problem.
Keywords: Pregnancy, Malaria, Nutrition, Low birthweight, Fetal growth restriction

Pregnancy and early childhood (the first 1000 days of life) are critical periods that determine short- and
long-term health outcomes [1]. In low- and middle-income countries (LMICs), two important barriers to a
successful pregnancy outcome are maternal undernutrition, which contributes to 800,000 neonatal deaths
annually [2], and malaria, estimated to cause approximately 900,000 low birthweight (LBW) deliveries
and over 100,000 infant deaths annually [3, 4]. Infant undernutrition, including fetal growth restriction
(FGR), contributes to 45 % of deaths in children under 5 years, and may lead to chronic disease in
adulthood [2, 5]. Ending the malaria epidemic and addressing the nutritional needs of children, adolescent
girls and pregnant women form key components of the recently-launched Global Strategy for Womens
Childrens and Adolescents Health for 20162030 [6]. The World Health Organizations (WHO)
Sustainable Development Goals include ending hunger and malnutrition; reducing maternal, newborn and
child mortality; and ending infections such as malaria [7]. In LMICs, populations are often affected by
both hunger and malaria [2, 8], and the two may interact (Fig. 1). Nutritional status and intake of specific
nutrients may affect immunity, modulating an individuals ability to control and clear infection [9]. In
turn, infection and associated inflammatory processes increase energy expenditure and protein
catabolism, draining nutritional reserves. Of the many potential nutrition-infection interactions in
pregnancy [10], malaria is especially important, being the leading preventable cause of LBW in Africa.
A growing body of evidence suggests that malaria and maternal undernutrition interact to worsen
pregnancy outcomes. However, interventions to protect pregnant women and their fetuses from
macronutrient undernutrition and gestational malaria remain poorly integrated. Our belief is that maternal
nutrient deficiency remains aneglected public health problem, and that few successful interventions in this
area have adequately dealt with malaria as a cofactor. In this call for increased collaboration between
malaria and nutrition experts, we discuss the evidence for malarianutrition interactions in pregnancy,
with a focus on macronutrient undernutrition, as this remains relatively understudied, notwithstanding the
importance of micronutrient deficiencies. Macronutrient undernutrition refers to insufficient consumption
of carbohydrates, fats and proteins, and is typically assessed using anthropometric measures in resource-
limited settings. We summarise currently available tools to prevent and treat macronutrient undernutrition
and malaria in pregnancy and outline key research questions that may advance our understanding of
gestational malaria nutrition interactions with a view to developing novel approaches to improve
pregnancy outcomes in LMICs.
Burden of malaria and macronutrient undernutrition in pregnancy
Each year, 125 million pregnant women, mostly in subSaharan Africa and Asia, are at risk of
malaria infection [8]. Worldwide, at least 10 % of pregnant women are undernourished, defined as a pre-
pregnancy body mass index (BMI) of less than 18.5 kg/m2, with prevalence being highest, again, in
LMICs in Africa and Asia [2]. Severe maternal undernutrition is rare outside of famine and conflict
situations, but moderate undernutrition is common, and associated with LBW [2, 11, 12].
Current evidence for malariamacronutrition links in pregnancy
There is evidence for geographical, socio-economic, temporal and mechanistic links between
malaria and macronutrient undernutrition (Fig. 1). Global distribution maps of malaria transmission and
undernutrition statistics clearly highlight a broad geographical overlap. Undernourished individuals,
including pregnant women, are more likely to live in economic and environmental circumstances that
favour malaria exposure [2]. Arguably, these overlaps in disease geography and exposure risk alone
provide sufficient proof of need to design interventions that prevent and treat both malaria and
undernutrition in pregnancy and infancy.
Malaria and macronutrient undernutrition in pregnancy are also linked temporally. In pregnant
Gambian women, the incidence of FGR, preterm birth (PTB) and malaria were all highest late in the
hunger season [13], the part of the rainy season before harvest begins. In the same setting, food
supplements (high-energy groundnut biscuits) had most impact on birthweight over this period [14].
These results suggest that simple environmental co-incidence of both conditions worsens pregnancy
outcomes (whether in an additive or synergistic manner remains unknown), and/or that acute
macronutrient shortages increase the risk and impact of gestational malaria (effect measure modification).
These findings urgently require confirmation.
Macronutrient undernutrition is associated with increased malaria morbidity and mortality in
children and non-pregnant adults, suggesting important immunological interactions [15, 16]. Malaria, in
turn, causes nutritional depletion and worsens child undernutrition [17]. Such interactions are likely to
exist in pregnancy [18]. Whether undernutrition alters pregnant womens risk of contracting malaria
infection is unknown, but in the Democratic Republic of Congo women with low mid-upper arm
circumference (MUAC) and low BMI were most likely to have high placental parasite loads [19].
Studies suggest that the effect of Plasmodium falciparum infection on fetal growth and
birthweight is more pronounced amongst women with macronutrient undernutrition compared to well-
nourished women [18, 20, 21]. In the Democratic Republic of Congo, the effects of maternal P.
falciparum parasitaemia on uteroplacental flow and fetal growth were most pronounced amongst
undernourished women (low MUAC or BMI) [18, 20]. Similarly, in Kenya, an association between
peripheral P. falciparum infection and reduced birthweight was only reported amongst women with a low
BMI [21].
Fetal and postnatal effects
While poor nutrition and malaria have important adverse consequences for maternal health, the
developing fetus is most affected. This can have severe immediate as well as long-term consequences
the foundations for an effective immune system, adequate growth, and short- and long-term health are
laid in utero [5]. Macronutrient undernutrition and malarial infection have been independently associated
with FGR, PTB and stillbirth [1, 11, 22], and the risk of adverse outcomes may be highest when pregnant
women are affected by both [18]. To date, it remains unknown whether malaria and undernutrition act
additively or even synergistically to affect pregnancy outcome, or whether effect measure modification of
the impact of malaria on birthweight by nutritional status is present [18].
Malaria and macronutrient undernutrition in pregnancy have each been associated with increased
infant morbidity and mortality. Many of the 900,000 LBW deliveries attributed to malaria take place in
areas where maternal nutrition is poor, but the extent to which undernutrition contributes to this burden is
unknown [3]. In utero exposure to malaria or undernutrition may affect the immunocompetence of the
offspring, and could thus alter the risk of malaria-related morbidity and mortality in infancy [5, 23, 24].
Gestational malaria and undernutrition have been associated with suboptimal postnatal growth, suggesting
in utero insults have lasting effects on the growth trajectory [25]. Growth faltering in utero and early
infancy results in short adult stature, itself a risk factor for LBW, highlighting the cyclical,
transgenerational effects of poor nutrition (Fig. 1) [26]. Moreover, LBW due to maternal macronutrient
deficiency has been epidemiologically linked to adulthood non-communicable diseases [5, 27, 28].
Effects of nutrition on antimalarial antibody
In undernourished children, research indicates that antibody responses to various infections
remain adequate, yet most such studies involve a small number of subjects and rarely assess antibody
functionality [29]. By contrast, there is evidence to suggest that undernutrition reduces immunological
response to vaccines [30] and diminishes antibody-mediated antimalarial immunity [31, 32]. Limited
studies have assessed the effect of maternal macronutrient undernutrition on acquisition or maintenance
of P. falciparum antibody responses. In pregnancy, the most important antibody target is PfVAR2CSA, a
parasite protein inserted in the surface of infected erythrocytes that mediates placental parasite
sequestration [33]. Susceptibility to malaria is greatest in first pregnancy, when women lack antibody to
the PfVAR2CSA protein [33], and this antibody has been correlated with protection against placental
malaria, LBW and anaemia [34].
In Papua New Guinea and Malawi, maternal MUAC was not associated with levels of antibody
to PfVAR2CSAexpressing infected erythrocytes but maternal weight was inversely correlated with
antibody levels to P. falciparum merozoite surface protein 2 and to PfVAR2CSA [35]. In a different
study, Malawian women with a BMI of less than 18.5 kg/m2 at first antenatal visit had higher antibody
levels to PfVAR2CSA at 36 gestational weeks than those with a normal or raised BMI [36]. A similar
relationship was found for low socio-economic status: the association between undernutrition and
antibody levels may be a result of increased exposure to malaria due to poor housing and limited access to
bed nets and antimalarials [36]. In the same cohort, lipid-based nutrient supplementation (LNS) during
pregnancy did not improve anti-malarial antibody responses [36]. To untangle the overlapping exposures
relating to malaria immunity and undernutrition, further randomised trials of interventions may be
Even if antibody levels or functionality are not affected, maternal macronutrient undernutrition
might affect the ability of phagocytic cells to clear infection [37]. Undernutrition and placental malaria
appear to reduce transplacental transfer of protective antibodies to some pathogens, but not to others [38,
39]. Malaria in pregnancy and undernutrition may also affect vaccine response in the offspring [29, 40]
such potential intergenerational effects require urgent evaluation.
Effects of malaria and nutrition on cellular immune responses
Pregnancy is characterised by a switch from a proinflammatory T-helper 1 (Th1) to a Th2
cytokine response, which protects the fetal allograft from rejection by the maternal immune system [41].
Although inflammation plays critical roles in implantation, placentation and birth, at other time points, it
may contribute to adverse pregnancy outcomes including LBW [41]. Placental malaria causes local
inflammatory cytokine and chemokine production, which is associated with LBW, PTB and FGR [33],
while macronutrient undernutrition has been associated with reduced T-cell activation (due to lowered
circulating glucose), a decrease in total T-cell numbers and an altered cytokine profile [42]. The impact of
the dysregulated cellular immune response in undernourished women on fighting malarial infection
remains poorly understood. Infections other than malaria are likely to play an important role too [43], in
particular if resulting in systemic and/or placental inflammation, which have been associated with adverse
pregnancy outcomes [44]. These infections may be more common and detrimental amongst
undernourished women.
Effects on fetal nutrient supply
Placental malaria affects transplacental transport of nutrients, including amino acids and glucose
[45]; this is most apparent when there is intervillositis (accumulation of malaria pigment-containing
mononuclear cells) [33]. In undernourished women, compensatory upregulation of transplacental amino
acid transport can occur in response to reduced amino acid availability [46], but this could be impaired by
placental malaria, thereby limiting fetal nutrient supply even further.
Effects on placental development
A growing body of evidence suggests that malaria infection in early pregnancy increases the risk
of adverse pregnancy outcomes independently of infections following organogenesis and placentation
[47]. While the impact of pre-conceptional malaria is unknown, nutritional status at conception has
important consequences for embryonic and placental development and fetal growth [48], and maternal
weight and gestational weight gain both influence placental weight [49]. Further, both malaria and
undernutrition are known to negatively affect trophoblast migration and invasion capacity [50, 51],
important determinants of the development of maternal placental blood flow. In Congolese women, early
pregnancy parasitaemia was associated with increased uterine artery resistance in undernourished but not
in wellnourished women [20]. Malaria and undernutrition may both affect vascular development of the
fetal placental circulation [52].
Effects of malaria and undernutrition on growth-related hormones
Leptin The adipokine leptin increases Th1 cell numbers and cytokine secretion [42]. Low levels
of leptin are seen in undernourished women [53] and are predictive of mortality in undernourished
children [54]; they have also been reported in placental malaria [55]. Nevertheless, the consequences of
suppressed maternal leptin for pregnancy outcome remain unknown.
Both protein-energy undernutrition and malaria infection are associated with elevated serum
cortisol levels [56, 57], which may translate into increased fetal cortisol exposure. Undernutrition can
reduce the function of 11 hydroxysteroid dehydrogenase, the gatekeeper for fetal cortisol exposure;
effects of placental malaria on its activity remain unknown [22]. Increased fetal cortisol levels have been
associated with reduced thymus size and impaired lymphopoiesis and with effects on the hypothalamus
pituitaryadrenal axis and on both cellular and humoral immunity [53].
IGF axis The IGF axis is a principal driver of fetal growth [22]. Inflammatory cytokines, such as
TNF and IL-1, produced in response to malaria decrease placental amino acid uptake [45] and decrease
IGF1 [22], as does undernutrition [58], suggesting malaria and undernutrition might act synergistically to
affect fetal growth. In utero stress can cause neuroendocrine changes that predispose to diseases such as
diabetes; altering the regulation of IGF levels may be one possible pathway [59].
The conundrum of co-existing macro- and micronutrient deficiencies Pregnant women with
macronutrient undernutrition are prone to concurrent micronutrient deficiencies, with iron deficiency
probably being the most common. Attempts should be made to take these into account when studying
malarianutrition relationships [15, 60]. In children, iron deficiency may protect from severe malaria, and
iron supplementation without antimalarial chemoprophylaxis exacerbates infection and mortality risk
[61]. Iron deficiency may reduce the risk of placental malaria [62], yet it increases the risk of maternal
anaemia and could cause LBW directly or via anaemia-dependent effects [63]. Iron supplementation
combined with adequate malaria prevention appears not to increase the risk of maternal Plasmodium
infection [6365]. Furthermore, both malaria infection and macronutrient malnutrition, particularly
protein deficiency, are causes of maternal anaemia, itself associated with LBW [2, 22]. Other infectious
causes of iron deficiency and anaemia, such as intestinal helminth infection, may also be important, given
their potential modifying impact on malaria, nutrient absorption and LBW risk [66, 67]. Folate
supplementation in pregnancy prevents neural tube defects, but may increase infection risk and, in high
doses, could result in failure of antifolate antimalarials [68]. Multiple micronutrient supplements decrease
LBW, FGR and stillbirths [69]; however, whether deficiencies of micronutrients such as zinc, calcium
and vitamin A interact with malaria in pregnancy remains unclear [70].
Assessment of macronutrient nutritional status in pregnancy
Assessment of maternal nutrition forms part of the WHOs focused antenatal care strategy [71],
which states that women with a low booking BMI (<18.5 kg/m2) should receive support. Many pregnant
women still seek antenatal care late, and BMI tends to increase as a result of gestational weight gain [12];
therefore, women who might benefit from nutritionmalaria interventions could be missed. MUAC varies
little over gestation, and can help to identify undernourished women who are at risk of delivering a LBW
baby [72], but cut-points for low MUAC and BMI may not identify the same women [72]. Maternal
height less than 155 cm (indicating childhood stunting) and low gestational weight gain are also
associated with PTB and FGR [26]. These measures need to be evaluated in relation to malaria risk,
although the best and most applicable nutrition-related predictor of adverse pregnancy outcome remains
to be clarified.
Current tools to combat malaria and macronutrient undernutrition in pregnancy
To protect pregnant women from malaria, the WHO currently recommends the use of insecticide-
treated bed nets, monthly intermittent preventive treatment with sulphadoxine-pyrimethamine from
second trimester onwards, and malaria case detection and management [73]. By contrast, current
management of macronutrient undernutrition is largely limited to dietary advice and improving womens
economic status, although studies demonstrate that balanced energy-protein supplements are beneficial
[74, 75]. Nevertheless, given the omnipresence of poverty, dietary advice may have limited effect in
LMICs [76].
Balanced energy-protein supplementation was shown to improve pregnancy outcomes and
increase birthweight by an average of 100 g in undernourished women [77]. In The Gambia, daily dietary
supplementation with high-energy groundnut biscuits (4.3 MJ/day) improved gestational weight gain and
increased birthweight; effects were greatest in primigravidae and in the hunger (malaria) season [14].
Lipid-based nutrient supplements (LNS) may be alternative strategies to improve birthweight and
gestational length. In Burkina Faso, daily LNS (1.56 MJ/372 kcal, 14.7 g protein and micronutrients)
increased gestational length amongst women with a low baseline BMI and anaemia and had greatest
impact during the rainy season [78]. In Ghana and Malawi, daily LNS (118 kcal, including 20
micronutrients) increased length (~45 mm) and weight (~50 g) at birth, and had greatest effects on birth
size amongst primigravid, anaemic and short-statured women (Ghana) [79]. In Malawi, LNS was most
beneficial in women who had HIV infection or malaria [80]. Multiple micronutrient and iron/folic acid
supplements may also significantly increase birthweight and reduce LBW and stillbirth, but effect sizes
tend to be modest [77]. Taken together these results suggest that nutritional supplementation may be most
beneficial in vulnerable women, such as primigravidae and women living with HIV, who have no or
impaired immunity to pregnancy-associated malaria and are at high risk of undernutrition, malaria and
LBW [22]. Adolescent women are another potential target group, being at increased risk of
undernutrition, malaria and adverse pregnancy outcomes [81].
Other approaches to improve maternal nutritional status whilst reducing malaria risk could be of
use. Intermittent preventive treatment with sulphadoxinepyrimethamine and azithromycin reduced the
risk of LBW, improved birthweight and gestational length, and prevented growth faltering in early
infancy in two of three clinical trials [82, 83]. In Papua New Guinea and Malawi, it was associated with
increased gestational weight gain (Ashorn P, unpublished observations) [12]. Beyond azithromycins
antimalarial effects, underlying mechanisms could involve reduction in maternal energy expenditure
following clearance of infections, increased appetite once infection resolves, increased nutrient
availability to the fetus, and effects on maternal gut microbiota that improve dietary energy harvest [84].
Infection and nutrition-related inflammatory processes have been associated with adverse pregnancy
outcomes, including PTB [44]. Azithromycin has anti-inflammatory activity and may clear other
infections responsible for inflammatory responses [83].
Building the evidence base
Many pregnant women are at risk of both undernutrition and malaria, yet few studies have
investigated gestational malarianutrition interactions. Given their potential consequences for fetal
growth and development, an expanded evidence base on malarianutrition interactions in pregnancy is
urgently needed, with closer collaboration between malariologists, nutritionists and reproductive health
specialists. Table 1 summarises current research gaps.
Better mapping the overlapping burdens of undernutrition and malaria infection in pregnancy
could be complemented by pooled analysis of data from pregnancy cohort studies that measured both
nutritional and malariometric indices to confirm effect measure modification of the malariabirthweight
relationship by nutritional status. Studies are needed in early pregnancy and periconceptionally [48],
when impacts on fetal development and immunological programming may be most profound.
Determining the long-term effects of malaria and undernutrition, and research that aims to untangle the
effects of mixed macroand micronutrient deficiencies for malaria immunity and placental malaria-
associated adverse pregnancy outcomes, are needed. Similarly, the impact of poor nutrition in pregnancy
on efficacy of malaria treatment and vaccines should be assessed.
Potential new interventions
There is mounting evidence that antenatal identification and tailored management of high-risk
mothers may prevent adverse pregnancy outcomes due to malaria and undernutrition, and further
research, such as pooled analysis, may provide additional evidence for this approach. Potential target
groups include adolescent, primigravid, undernourished, HIV-infected or anaemic women. These women
in particular may benefit from enhanced malaria prevention strategies combined with effective nutritional
supplementation, which can be delivered conjointly through antenatal care systems. Drugs that improve
gestational weight gain in undernourished women, or that clear other deleterious infections (e.g.
Chlamydia trachomatis) whilst providing antimalarial protection, also deserve further evaluation [12, 83].
Macronutrient undernutrition, alone and in concert with placental malaria, can deleteriously impact fetal
growth, and could affect both immunocompetence (and infection risk and mortality in the offspring), and
long-term health. To meet the World Health Assemblys targets for improving nutrition status, including
decreases in maternal anaemia and LBW, improvement of malaria prevention will also be necessary given
the major contributions of malaria to both LBW and anaemia. Joint efforts by nutritionists and malaria
experts are needed to determine the burden and significance of malaria-nutrition interactions in
pregnancy, and to develop interventions that protect pregnant women and their children from this
dangerous dyad.