Exercise as it relates to Disease/The effects of aerobic exercise during pregnancy on infant neuromotor skills

This is a critical analysis of the journal article from Medicine and Science in Sports and Exercise: "Effects of Aerobic Exercise during Pregnancy on One-Month Infant Neuromotor Skills" by McMillan AG, May LE, Gaines GG, Isler C, Kuehn D (2019).

What is the background to this research?
The purpose of this article is to determine the effects of exercise during pregnancy on the development of infant neuromotor skills at one-months old. The prevalence of childhood obesity continues to increase as nearly one third of children aged 2-19 years in the United States meet the criteria for overweight or obese. Increased childhood obesity is linked to decreased physical activity levels and poor motor skill performance within early childhood. Studies of maternal obesity also report infant motor skills to be delayed and linked to long term consequences of cognitive function. Therefore, the earliest intervention to decrease this trend occurs within the prenatal period. This study hypothesised that aerobic exercise during pregnancy would be associated with higher neuromotor scores in infants at one month of age, based on standard paediatric assessments of motor skills which include reflexes, stationary and locomotion. The link between infancy and motor competence is important to understand as motor competent children are more likely to enjoy movement and therefore participate more in physical activities. Children are also more likely to have a decreased risk of obesity and other chronic diseases such as cardiovascular disease and diabetes when they obtain a positive association with movement.

Where is the research from?
This is an American study, conducted at the East Carolina University in Greenville, North Carolina. Dr Amy Gross McMillan is the leading researcher for the study as she obtains extensive background knowledge and specialises within the field of paediatric obesity. The study was funded by the American Heart Association and by the East Carolina University, these organisations held no influence to the study design, interpretation of data or writing and submission of the manuscript. This study was published within the Journal of Medicine and Science in Sports and Exercise in February 2019.

What kind of research was this?
The research conducted was a Randomised Control Trial (RCT). This study design is the most precise way to determine the effectiveness of whether a cause-effect relationship exists between the intervention and the outcome. Participants were randomly assigned to either a supervised exercise group or a non-exercise group where the outcome of the intervention was determined through the performance of infant neuromotor skills at one month old.

What did the research involve?
Seventy-one healthy pregnant women aged between 18-35 years with a pre-pregnancy BMI between 18.5-34.9 kg/m2 and all pregnant with a single foetus were selected for this study. All women were healthy, not using any current medications, non-smokers and had no history of alcohol or drug use during their pregnancy. Participants who also obtained any other contraindications to exercise during pregnancy such as diabetes mellitus, cardiovascular disease, hypertension or any other factors known to effect foetal wellbeing were excluded from the study. These women were randomly assigned to either an aerobic exercise intervention or a non-exercise group. Participants assigned to the exercise group performed 50 minutes of moderate-intensity, supervised aerobic exercise three times per week, whilst the participants in the non-exercise group maintained their usual activities. Infant neuromotor skills were measured at one month of age using the second edition of the Peabody Developmental Motor Scales (PDMS-2). This study focused on implementing a supervised exercise intervention. The use of this method enhanced the compliance of participants with roughly 89% of pregnant women performing three 50-minute sessions of aerobic activity per week.

Although there was high compliance this study did have some limitations. The sample size was relatively small for this intervention and although a diverse population of healthy women pregnant with a single child participated, results cannot be generalised for all pregnant women, especially those considered high risk due to multiple gestations or co-morbidities. This intervention didn’t control for factors such as diet, sleep, sedentary behaviour, occupation and postnatal infant stimulation and environment which could also influence the development of their nervous system and neuromotor control. Another limitation is that this study only focused on the performance of motor skills at one month, there was no later check-in to assess neuromotor ability at another milestone age. Finally, this study only focused on the effects of aerobic exercise rather than other forms of exercise (i.e., resistance or circuit) and their potential benefits on infancy motor skills.

What were the basic results?
Infants of women within the exercise group obtained higher PDMS-2 scores in comparison to infants of mothers in the non-exercise group; females also had higher scores compared to male infants. These results were interpreted by researchers as the findings confirmed their hypothesis that; infants of mothers who exercised during pregnancy scored higher on stationary, locomotive and reflex motor skills in relation to infants of mothers who did not exercise during their pregnancy. Exercise during pregnancy has therefore been proven to positively impact the infants developing systems allowing for improved neuromotor development, ultimately leading to the outcome of infants who are more proficient with movement and more likely to be active. It is also possible that women who exercised during pregnancy are more likely to provide a stimulating postnatal environment to enhance their child's development.

What conclusions can we take from this research?
The findings of this study are consistent with other research within this field, reporting positive outcomes of exercise during pregnancy on neuromotor behaviour and development of newborns. Increased maternal exercise for both the mother and child are shown to positively affect the incidence of many diseases and alleviate the risk of childhood obesity. This study only identified the effects of one form of activity and obtained a relatively small selection of participants. Future areas of research, could demonstrate the effects of further exercise interventions across a more diverse population of pregnant women.

Practical advice
Excessive gestational weight gain (GWG) can increase complications during pregnancy for both the mother and her child. Complications for the mother include gestational diabetes, hypertension, pre-eclampsia and obesity; whilst complications for the unborn child include the risk of respiratory syndromes, diabetes, cardiovascular disease and obesity. Therefore, staying active during pregnancy has many benefits for the health of both the mother and child, Australian Physical Activity Guidelines during pregnancy outline a total of either 2.5 to 5 hours of moderate intensity activity, 1.25 to 2.5 hours of vigorous intensity activity or a combination of both moderate and vigorous physical activity as well as strengthening activities performed at least 2 days per week. Physical activity during pregnancy doesn’t have to be vigorous to be beneficial; examples for aerobic and resistance exercises include walking, cycling, swimming and light resistance activities. As pregnancy progresses, it is important to modify physical activities and limit or avoid certain activities; consulting with a doctor is the best way to determine what type of activity would better suit the mother and the unborn child.

For healthy infant development from birth to one year, the Australian Physical Activity Guidelines address that physical activity should be supervised and predominantly floor based. Activities and movement help the infant to keep their minds active, develop senses of sight, touch and hearing, build strength, balance and posture as well as encourage the development of self-confidence and independence. The promotion of movement activities for infants are important as capabilities of motor control in early ages of their development link to physically active behaviours in adolescence and adulthood.

Further information/resources

 * Australian Physical Activity Guidelines for Pregnancy: https://www.health.gov.au/health-topics/physical-activity-and-exercise/pregnancy
 * Australian Physical Activity Guidelines for Birth to 1 Year: https://www1.health.gov.au/internet/publications/publishing.nsf/Content/gug-indig-hb~phys-0-1
 * Exercise Modifications During Pregnancy: https://www.pelvicfloorfirst.org.au/pages/exercise-modifications-during-pregnancy.html
 * Development of Infancy Motor Skills: https://www.pregnancybirthbaby.org.au/toddler-development-motor-skills
 * World Health Organisation Obesity and Overweight Fact Sheet: https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight