Date of Award

2016

Degree Name

Doctor of Philosophy (College of Health Sciences)

Schools and Centres

Health Sciences

First Supervisor

Professor Beth Hands

Second Supervisor

Professor Max Bulsara

Abstract

Longitudinal studies are important to fully understand the processes of neurological development during gestation and how risk factors present during this time impact motor development outcomes, yet few to date have focused on this critical time period.

The purpose of this study was to identify modifiable risk factors influencing motor development during the prenatal period. Of particular interest was finding out whether these risk factors differed between the sexes.

Participants (N=2900) were from the Western Australian Pregnancy Cohort (Raine) Study. The Raine Study began in May 1989 and women were recruited between 16-20 weeks gestation (m = 18 weeks) from the main obstetric hospital in Western Australia (W.A.), King Edward Memorial Hospital. Approximately 100 participants per month were recruited, with the process completed during November 1991. The women were primarily Caucasian, from European descent (88.2%), and included mothers who identified as Aboriginal (2.4%), Chinese (4.4%), Indian (2.6%), Polynesian (0.9%) and Vietnamese (0.3%). Recruitment criteria included adequate English language skills for the understanding of the study process and a desire to reside in W.A. to facilitate future follow up. There were 2868 live births and extensive obstetric, antenatal and sociodemographic data were recorded. Maternal and child health data were collected in a series of data collection phases at ages 1, 2, 3, 5, 8, 10, 14, 17, and 21 years. Motor coordination was measured at 10 (n = 1622), 14 (n = 1584) and 17 (n = 1221) years using the McCarron Assessment of Neuromuscular Development (MAND) (McCarron, 1997). The Neuromuscular Development Index (NDI) of the MAND was used as a continuous outcome measure.

Potential risk factors for a poorer motor outcome, including maternal smoking, alcohol and drug consumption, maternal age, parental handedness, maternal health (illness and infection), delivery mode, gestational hypertensive status, stress, socioeconomic status, percentage of optimal birth weight (a measure of whether growth potential has been met), child’s sex, gestational age, parity and breastfeeding were examined. Cross sectional analyses comprising chi-square tests, t-tests and univariate ANOVA models (general linear model - GLM) with Bonferroni post hoc correction were used to identify variables that contributed to motor development outcomes. The effect of these variables on motor development were further examined using linear mixed models accounting for the unbalanced nature of longitudinal data with repeated measures. A series of studies were conducted to analyse the impact of these factors on long term motor development outcomes.

The first study found that maternal hypertensive disease, in particular preeclampsia, had negative long term effects on motor development outcomes. The second study examined the number, timing and type of stressful events mothers experienced during pregnancy. A significant relationship between number of stressful events and motor development outcomes was revealed, suggesting increased stress led to suboptimal neurological development. Stress later in pregnancy was found to have a greater effect than earlier stress. The impact of breastfeeding duration was investigated in the third study and a protective effect was found for those who were breastfed for six months or longer compared to those who were breastfed for less than six months.

When males and females were examined separately in the fourth study there were some differences in the type of factors that affected motor development outcomes. Maternal preeclampsia, mode of delivery and income affected both male and female motor outcomes. Lower percentage of optimal birth weight was related to a lower male NDI. Younger maternal age, smoking during early pregnancy and stress during later pregnancy were related to lower NDI in females.

Other factors considered in the analyses, including lower family income, male sex, maternal alcohol consumption, smoking and caesarean section delivery were also found to negatively impact motor development outcomes. This information can be utilized to help identify potentially at risk infants and ensure optimal future neurological development. Early detection and intervention strategies may help to increase motor development outcomes in those who are exposed to the identified risks.

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