Genetic Evidence for Causal Relationships Between Maternal Obesity-Related Traits and Birth Weight

Hannah Webb, Mercer University College of Pharmacy

It is stated that on average, neonates born to overweight or obese women are larger than those neonates born to normal-weight women. Maternal overweight and obesity are considered to be risk factors for gestational diabetes. It is known that even in the absence of diabetes and when following the same controlled diet, obese women have an average reading of 7.2 mg/dL higher glucose levels than normal-weight women. [1]

Title: Genetic Evidence for Causal Relationships Between Maternal Obesity-Related Traits and Birth Weight
Design Meta analysis of 18 community based studies; N= 30,487
Objective To test for genetic evidence of casual association of maternal body mass index (BMI) and related traits with birth weight
Study Groups N/A
Methods Single-nucleotide polymorphism (SNP) genotype data were used from 30,487 women participating in 18 population or community-based studies
Duration N/A
Primary Outcome Measure Offspring birth weight from 18 studies
Baseline Characteristics Babies were born from the United Kingdom, Germany, the United States, Denmark, Canada, the Netherlands, Australia, Norway, and Finland.
Results Study Source Offspring birth weight (grams)
Fraser et al, 2013 3,481
Schlemm et al, 2010 3,472
Power and Elliott, 2006 3,325
Power and Elliott, 2006 3,379
Zhao H et al, 2009 3,440
Bisgaard, 2004 3,560
Nohr et al, 2009 3,643
Olsen et al, 2001 3,595
Knight et al 3,512
Lacroix et al, 2013 3,448
Jaddoe et al, 2012 3,528
Metzger et al, 2008 3,557
Mangus et al, 2006 3,526
Rantakallio, 1969 3.525
Boomsma et al, 2006 3,469
Medland et al, 2009 3,344
Nalatteru et al, 2013 3,365
Moayyeri et al, 2013 3,365
Adverse Events Common Adverse Events: N/A
Serious Adverse Events: N/A
Percentage that Discontinued due to Adverse Events: N/A
Study Author Conclusions Genetically elevated maternal BMI and blood glucose levels were potentially causally associated with higher offspring birth weight, whereas genetically elevated maternal SBP was potentially causally related to lower birth weight. If replicated, these findings may have implications for counseling and managing pregnancies to avoid adverse weight-related birth outcomes.

The causal relationship between birth weight and maternal obesity-related obesity remains uncertain. This meta-analysis was able to determine that genetically elevated maternal BMI and blood glucose levels were potentially causally associated with higher offspring birth weight. This leads to an increase in the risk of birth complications and opens the door to have implications for counseling and managing pregnancies to avoid adverse weight-related birth outcomes.

References

Tyrrell, Jessica, Rebecca Richmond, Tom Palmer, Bjarke Feenstra, Janani Rangarajan, Sarah Metrustry. Genetic Evidence for Causal Relationships Between Maternal Obesity Reltaed Traits and Birth Weight. The Journal of the American Medical Association. 2016; 315: 1129-1140.

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