The impact of microbial and inflammatory exposures on birth outcomes in rural Zimbabwe

One in seven babies in Africa are born with low birthweight, either because they are born too small (small-for-gestational age; SGA) or born too soon (preterm). Babies born SGA or preterm have a higher risk of dying, and do not grow as well in early life, leading to a higher risk of malnutrition. The most common form of malnutrition (stunting) affects health into adulthood, reduces learning at school, and lowers earning potential. To reduce child deaths and improve health, growth and prosperity throughout life, it is essential to improve birthweight. To do this, we need to understand the processes during pregnancy that lead to SGA and preterm.

The fetus depends on a delicate balance of processes to grow properly and be delivered on time. Infections during pregnancy, and activation of the body's defence system to tackle infections (called inflammation) may disturb these processes, leading to SGA and preterm birth. Mothers with sexually transmitted infections, urinary tract infections, gum disease or diarrhoea during pregnancy have a higher risk of SGA and preterm birth. Inflammation can also occur even when a pregnant woman is not sick with an infection. There are trillions of bacteria in the body, called the microbiome, which generally do not cause disease. However, a change in composition of the microbiome can cause inflammation. Unbalanced vaginal, oral and gut microbiomes in pregnant mothers have all been associated with SGA and preterm birth, although most of these studies have been done in high-income countries. It is unclear whether and how disturbed microbiomes cause inflammation, SGA and preterm birth in Africa.

We believe that taking antibiotics in pregnancy could improve birth outcomes by reducing harmful infections and inflammation. In order to test this, we will take advantage of an existing trial examining whether a daily antibiotic (called cotrimoxazole) during pregnancy can increase birthweight. We previously found that this antibiotic reduces inflammation as well as preventing infections. During the new study, 1000 women in rural Zimbabwe will receive either cotrimoxazole or placebo from the time they first book their pregnancy at the local clinic up until birth. The treatment will be decided randomly, like the flip of a coin. During pregnancy, oral samples (tongue swabs, dental plaque, saliva), vaginal swabs, stool, urine and blood will be collected from all mothers when they book and at 26, 34 and 36 weeks into pregnancy.

Our first aim is to see whether infections and inflammation during pregnancy are associated with SGA and preterm birth. Women will be examined by a dentist to check their oral health and be tested for sexually transmitted infections, urine infections and diarrhoea, with treatment provided if needed. Using the oral, vaginal and stool samples collected from booking and the end of pregnancy, we will study the microbiome and inflammation to see if they are linked to SGA and preterm birth. Our second aim is to compare the microbiome and inflammation in 100 women receiving the antibiotic and 100 women receiving placebo. We will see whether cotrimoxazole reduces inflammation, infections, or changes the microbiome during pregnancy. We will also test whether bacteria become resistant to the antibiotic. Our third aim is to see what effect maternal antibiotics have on the baby. We will collect samples of the placenta, blood and stool at birth, and collect stool and blood again when they are 4 weeks old, to compare infections, microbiome and inflammation in babies whose mothers received antibiotics or placebo in pregnancy.

Through this project, we hope to understand whether infections, microbiome disturbances and inflammation during pregnancy cause SGA and preterm birth, and exactly how the antibiotic works (if at all). This is important, because we may be able to design new treatments that can be given during pregnancy to help babies grow better and be born on time.

Children born small-for-gestational age (SGA) or preterm have elevated mortality. Together, SGA and preterm lead to low birthweight and increased risk of stunting, which impairs lifelong health and human capital. New interventions to reduce SGA and preterm are needed to reduce mortality and end stunting.

We hypothesise that maternal dysbiosis and inflammation at multiple sites in pregnancy drive SGA and preterm birth. A combined antimicrobial and anti-inflammatory intervention in pregnancy may modulate microbial and inflammatory exposures and improve birth outcomes. We will capitalise on a placebo-controlled, randomised trial of cotrimoxazole among pregnant women in rural Zimbabwe to longitudinally characterise oral, intestinal and vaginal dysbiosis and inflammation; evaluate their associations with SGA and preterm birth; and study the effect of cotrimoxazole on these mechanistic pathways.

We will undertake 3 specific aims:

1) Characterise microbial and inflammatory exposures during pregnancy and their association with adverse birth outcomes: We will compare microbiome characteristics and inflammation in oral samples, vaginal swabs and stool samples collected at baseline and late pregnancy from mothers of SGA, preterm and AGA/term infants, and evaluate associations between microbial and inflammatory exposures and adverse birth outcomes.

2) Determine the impact of cotrimoxazole on maternal microbiomes and inflammation: We will compare oral, gut and vaginal microbiomes, local and systemic inflammation between women randomised to cotrimoxazole or placebo (N=100/arm).

3) Determine whether maternal cotrimoxazole confers neonatal health benefits: We will compare linear growth, hospitalisation, microbiome and inflammation between infants of mothers randomised to cotrimoxazole or placebo at delivery and 4 weeks (N=100/arm). We will characterise inflammation and immune function in placenta and cord blood, and assess vertical pathogen transmission and AMR.

Who might benefit from this research?
The ultimate beneficiaries of this research are mothers and their infants in low- and middle-income countries, where the burden of preterm birth, SGA and their associated long-term sequelae occur. Small for gestational age (SGA) accounts for 22% of all neonatal deaths and preterm birth is the leading cause of under-5 mortality. These adverse birth outcomes are also major predictors of child stunting, which affects one quarter of children globally and impairs health and human capital across the life-course. In the setting where this study will take place (Shurugwi, Zimbabwe), 14% of newborns are SGA and 17% preterm (SHINE trial data). This is consistent with national statistics for Zimbabwe, placing the country in the top six worldwide for preterm birth prevalence. This proposal therefore, will benefit a community with a heavy burden of adverse birth outcomes. Identifying the root causes of adverse birth outcomes and subsequently reducing their burden in LMIC will benefit mothers, children and entire communities through improved health, wellbeing, resilience, productivity and prosperity.

This project builds on our recent findings in the same community through the SHINE trial, in which we showed that improved infant feeding modestly reduced stunting by 20%, while improved water, sanitation and hygiene had no effects. Given the limit impact of these interventions, we now want to improve child health further by intervening earlier in the life-cycle and concurrently investigating the prenatal causes of poor growth. The current proposal builds on an existing placebo-controlled randomised trial of cotrimoxazole during pregnancy to improve birthweight, thereby ensuring its feasibility. Importantly, this proposal will improve our understanding of the causes and underlying mechanisms of adverse birth outcomes which remain poorly characterised in LMIC. This simultaneous approach, combining a novel intervention with mechanistic sub-studies, will ensure that we gain a rigorous understanding of the potential of such interventions to benefit the large populations currently bearing the burden of SGA and preterm birth.

How might they benefit from this research?
This proposal will build upon an existing trial examining the effect of cotrimoxazole on birthweight, thereby ensuring its feasibility. Participants will directly benefit from increased clinical assessments included in this proposal, including a detailed oral health assessment with provision of emergency treatment, and screening for sexually transmitted infections, with appropriate treatment. Infants will be followed in a dedicated study clinic at 4 weeks of age, where any clinical problems will be addressed. Members of the community will be engaged through our engagement pathways about dental hygiene and the role of infections in adverse birth outcomes. Community members will also benefit through active engagement in the study planning process, through establishment of an advisory board to ensure feasibility. In the long-term, communities with a high burden of adverse birth outcomes globally will benefit through better understanding of the impact of inflammation and microbial exposures in SGA and preterm birth. This will ultimately lead to improved targeted preventative therapies to reduce SGA and preterm prevalence, and thereby improve child growth and potential across the life course. Poor child growth is associated with reduced economic potential, therefore the broader impact of large-scale improvements in child growth will result in greater economic potential, prosperity and potential in LMIC.