Conclusions and Recommendations
The findings of this research indicate that TPO positivity is associated with reduced brain growth measurements at delivery; however, the relationship appears to be modified by maternal
race/ethnicity. The difference in brain growth measurements may be more noticeable among the White non-Hispanic racial/ethnic group because they are more likely than their non-white
counterparts to deliver later term, thus allowing the differences in brain growth variables to be more apparent. Whereas, non-white mothers have a tendency to deliver earlier term infants who may not have had the opportunity to reach full potential, thereby masking the effects of TPO influence. Significant differences were not observed in other anthropometric
measurements (e.g., birth weight, birth length).
Results of this dissertation also demonstrated that infants born to TPO+ mothers have a smaller head circumference and weigh less at birth but essentially catch-up in growth between 3 to 6 months of age. The birth to 3 month timeframe appeared to be the most significant period for catch-up growth for infants of TPO+ mothers. Exploratory analyses suggested that TPO positivity and subsequent postpartum thyroid dysfunction may be considered on a continuum in regards to certain infant growth measurements, as the impact of reduced head circumference and accelerated catch-up growth was more significant among infants born to mothers who developed postpartum thyroid dysfunction as compared to infants born to mothers who were TPO+ only. This analysis was under-powered to detect any differences in neurocognitive outcomes of infants.
Future studies with larger sample sizes are indicated to confirm the results obtained in this dissertation, particularly those results that did not quite reach statistical significance. For instance, this analysis suggested that antenatal TPO positivity may result in reduced infant abdominal circumference (β = -0.380 (SE = 0.210; p<.08)). This finding is worthy of further investigation, as reduced abdominal circumference measurements are indicative of impaired fetal liver growth in utero, which may impact postpartum infant growth. Additionally, future research should employ a larger sample size to explore more in-depth the influence of various potential confounders (e.g., breastfeeding habits, maternal obesity, maternal education, etc) on the relationship between TPO and/or PPTD status on infant outcomes.
Epigenetic studies may be warranted to identify any genetic variants or single nucleotide
polymorphisms (SNPs), which could elucidate the interaction between maternal TPO status and race/ethnicity. Epigenetic analysis may prompt ethnic-based screening for TPO autoantibodies.
Considering the long-term implications of impaired fetal/newborn growth, it is important to identify avenues for early prevention and intervention. Maternal thyroid antibody status during pregnancy may be one of those factors that play a role in fetal growth impairment but is currently being overlooked due to lack of consensus on maternal testing and treatment. At present, TPO antibody status is not assessed as part of the standard prenatal care laboratory work-up, but this study suggests that fetal brain growth may be impaired by TPO positivity among certain populations, therefore, autoantibody screening among high-risk sub-groups may be useful for clinicians to determine whether prenatal thyroid treatment is warranted. Future research should also focus on determining the potential impact of reduced head circumference and accelerated growth as it relates to long-term neurocognitive outcomes.
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