It is widely acknowledged that maternal obesity and excessive gestational weight gain (GWG) are associated with increased risk of fetal macrosomia and recent studies have suggested a role for the timing and composition of GWG.
To examine the effect of the rate of change in GWG and maternal upper-body subcutaneous fat on neonatal anthropometric outcomes in a pilot observational study amongst women with obesity.
Expectant women with a body mass index (BMI) > 30 kg/m at first antenatal appointment were recruited at 12 weeks gestation. Maternal height, weight and skinfold thickness (SFT) measurements were collected at baseline and repeated at 28 and 36 weeks gestation. Following delivery, World Health Organisation (WHO)-UK infant birthweight z-scores were calculated, and infant anthropometric measurements were obtained.
The sum of upper body SFT measurements increased in mid-pregnancy (0.08 ± 0.71 mm/week) and decreased in late pregnancy (-0.04 ± 1.17 mm/week). After adjustment for maternal age, BMI and parity, mid- but not late- pregnancy GWG was positively associated with infant birthweight z-score (p<0.05), while mid- but not late-pregnancy changes in the sum of SFT were inversely associated with infant birthweight z-score (p<0.01).
The present study suggests that mid- rather than late-pregnancy changes in weight and upper-body subcutaneous fat are associated with infant birthweight. Further research is required in larger, more diverse populations to explore whether pregnancy interventions aiming to improve maternal and offspring health can be personalised beyond BMI and GWG.

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