American Journal of Clinical Nutrition Supplement: Prevention Options for Preterm Birth, Fetal Growth Restriction, and Small Birth Size

Low birth weight, defined by the World Health Organization (WHO) as a birth weight of less than 2,500 grams, or about 5.5 pounds, has been linked to a risk of growth faltering in infancy, poor lung function and fitness, chronic non-communicable diseases as well as early life mortality.  Low birth weight can result from preterm birth or fetal growth restriction in which the newborn infant presents as small for gestational age.  Globally, 15 to 20% of all infants are born with low birth weight, with the highest prevalence in Sub-Saharan Africa and South Asia.

Published as a Supplement to The American Journal of Clinical Nutrition (AJCN), Prevention Options for Preterm Birth, Fetal Growth Restriction, and Small Birth Size reviews the effectiveness of interventions designed to reduce the incidence of adverse birth outcomes, including interventions centering on nutrition, psychosocial support, infection control, and environmental remediation.  Overall, these reviews help dietitians and other health care providers determine which interventions are likely to work as well as where more research is needed to improve birth outcomes globally.  This supplement is sponsored by Tampere University, Faculty of Medicine and Health Technology, with grant support from the Children’s Investment Fund Foundation.

Below is a brief summary of the five articles published in the Supplement:

Antenatal Interventions to Reduce Risk of Low Birth Weight Related to Maternal Infections during Pregnancy

Maternal infections during pregnancy have been linked to an increased risk of poor birth outcomes.  Seeking to better understand how key interventions targeting maternal infections affect birth outcomes, Yvonne Muthiani et al. reviewed the scientific literature.  Specifically, the authors sought evidence from randomized controlled trials as well as reviews of randomized controlled trials, leading them to 15 antenatal intervention studies of pregnant women that reported low birth weight, preterm birth, small for gestational age, or stillbirth as outcomes.  According to the authors’ findings, “there is insufficient data on the intervention efficacy of several key interventions and outcomes of interest, despite a strong rationale and impetus to address maternal infections to reduce adverse outcomes.”  For example, the authors pointed to an association between maternal periodontal disease and low birth weight.  In most of the intervention trials under review, however, periodontal treatment started during the second trimester.  “By this time it may be too late to address inflammatory responses to periodontal pathogens.”

What More Can Be Done? Prioritizing the Most Promising Antenatal Interventions to Improve Birth Weight

WHO has published recommendations for antenatal interventions to reduce low birth weight.  Estimates, however, suggest that even if the current WHO recommendations were fully scaled up, the impact would fall short of WHO’s targets.  In response, Annariina M. Koivu et al. conducted a prioritization exercise to identify the most promising antenatal interventions not currently recommended by WHO that could further reduce the global prevalence of low birth weight.  To conduct this exercise, the authors employed an adapted version of the Child Health and Nutrition Research Initiative method, created to set priorities in global child health research.  The exercise led to six recommendations: (1) multiple micronutrients, (2) low-dose aspirin, (3) high-dose calcium, (4) prophylactic cervical cerclage, (5) psychosocial support for smoking cessation, and (6) other psychosocial support for targeted populations and settings.  The authors believe that “these promising interventions, coupled with increasing coverage of currently recommended antenatal care, could accelerate progress toward the global target of a 30% reduction in the number of low-birth-weight infants born in 2025 compared to 2006-10.”

A Modular Systematic Review of Antenatal Interventions to Address Undernutrition during Pregnancy in the Prevention of Low Birth Weight

Poor nutrition during pregnancy can lead to adverse birth outcomes.  In search of solutions, Patricia J. Hunter et al. explored the effectiveness of seven antenatal nutrition interventions on reducing low birth weight, preterm birth, small for gestational age, and stillbirth, working with the results of randomized controlled trials.  For their analysis, the authors relied on a recently developed systematic review method, the modular review, that enables the review of multiple related interventions.  The review’s findings suggest that “provision of balanced protein and energy, multiple micronutrients, and lipid-based nutrient supplements to pregnant women in populations with undernutrition can reduce the risk of low birth weight and related outcomes.”  On the other hand, the authors found that “the benefits of omega-3 fatty acids and calcium supplementation to this population require further investigation.”  In summary, the authors believe that “the path to the birth of the thriving newborn involves holistic approaches to nutrition and its seamless integration in a complete program of social, environmental and medical support.”

Antenatal Interventions to Address Harmful Behaviors and Psychosocial Risk Factors in the Prevention of Low Birth Weight

There is increasing recognition that psychosocial factors such as smoking, alcohol use, depression, stress, and partner violence are associated with a higher risk of adverse birth outcomes.  In response, the authors of this systematic review of randomized controlled trials to assess the effect of 11 antenatal interventions designed to ameliorate the impact of psychosocial risk factors on adverse birth outcomes.  According to their findings, of the 11 reviewed interventions, “professionally provided psychosocial support during pregnancy in general and specifically as a means to reduce smoking can potentially contribute to improved newborn health.”  On the other hand, the other interventions under review “either appear not to be effective in preventing adverse birth outcomes or there is little evidence in any direction regarding the efficacy.”  Calling for more research, the authors noted that the majority of the randomized controlled trials they reviewed were conducted in high-income countries and that their findings could not necessarily be applied to low- and middle-income countries.

A Modular Systematic Review of Antenatal Interventions Targeting Modifiable Environmental Exposures in Improving Low Birth Weight

Many modifiable environmental exposures are known to be risk factors of poor birth outcomes, including air and environmental pollutants, household cooking fumes, and poor sanitation and hygiene.  This prompted Pieta K. Näsänen-Gilmore et al. to review eight interventions designed to improve birth outcomes by reducing harmful environmental exposures.  Overall, the authors found that “there is a paucity of evidence from randomized controlled trials on interventions that modify environmental risk factors during pregnancy to potentially improve birth outcomes.”  In particular, the authors noted that the evidence indicated that interventions designed to reduce indoor air pollution were not likely to reduce the prevalence of adverse birth outcomes.  The authors, however, cautioned that “lack of evidence does not necessarily signal lack of effect,” noting that “the effect of interventions reducing environmental risk factors may be harder to quantify or separate from other socio-behavioral factors, which may influence the success of the intervention.”

We invite you to explore this AJCN Supplement in its entirety to gain a deeper understanding of what we can do as nutritionists and health care providers to improve birth outcomes as well as to learn where more research is needed.