INTRODUCTION
Obesity is a significant public health concern. There is a rising trend
for increased body mass index (BMI) across all age groups with obesity
rates tripling over the past 40 years 1. The World
Health Organization (WHO) reported that 39% of adults aged 18 years and
over were overweight in 2016, and 13% were obese with obesity being a
major risk factor for non-communicable diseases including type 2
diabetes and cardiovascular diseases 2. A global
systematic analysis found that women of reproductive age demonstrate a
particularly steep increase in obesity prevalence 3,
with 38.9 million pregnant women estimated to be overweight and 14.6
million estimated to be obese, in 2014 4. In
Australia, nearly half of women who gave birth were overweight or obese
in 2017 5. A similar trend in overweight and obesity
prevalence has also been seen in men of reproductive age3.
There is consistent evidence that maternal preconception BMI affects
infant birthweight, such that maternal overweight or obesity increases
the likelihood for an infant being born large for gestational age (LGA)
(OR=1.45; 95%CI=[1.29, 1.63] and OR=1.88; 95%CI=[1.67, 2.11],
respectively) or macrosomic (OR=1.70; 95%CI=[1.55, 1.87] and
OR=2.92; 95%CI=[2.67, 3.20], respectively) 6. In
comparison the risk of delivering a small for gestational age (SGA) baby
are increased in underweight mothers (OR = 1.67; 95% CI =
[1.49-1.87]); but decreased with overweight (OR=0.71;
95%CI=[0.66, 0.76]) or obese mothers (OR=0.88; 95%CI=[0.78,
0.99]) 6. Increased maternal BMI also influences
child overweight and obesity risks up to 14 years of age7 and increases future risk for obesity and
cardio-metabolic diseases later life for both mother and child8. Problematically, the potential impact of paternal
BMI is rarely considered in these studies, despite a small body of
evidence suggesting that paternal preconception overweight and obesity
may also contribute to infant birthweight including the delivery of an
SGA or LGA infant 9, 10. Thus the involvement of
paternal overweight and obesity on infant birthweight demonstrates a
role for the father’s preconception health in programing fetal outcomes11.
It is evident that maternal preconception BMI affects infant
birthweight, however the influence of paternal preconception BMI is less
studied. Further it is unclear whether there is an additional effect on
infant birthweight if both parents are overweight or obese. We
hypothesise that the combination of both maternal and paternal
preconception overweight/obesity has a larger contribution to infant
birthweight than their independent parental effects. The objective of
this study is to assess the independent and combined effects of maternal
and paternal preconception overweight and obesity on infant birthweight
utilising an assisted reproductive technologies (ART) cohort where
preconception parental BMI is routinely collected.