Background: Observational studies demonstrate significant associations between pre-pregnancy obesity (defined as BMI≥30 kg/m2) and adverse pregnancy outcomes (e.g. gestational diabetes mellitus [GDM]). Although BMI is a good indicator of population health, there is strong evidence in non-pregnant populations that it is a poor indicator of individual risk compared with alternative (e.g. waist circumference). There is a lack of comprehensive evidence on alternative measures to BMI in pregnancy. This systematic review aimed to identify associations between alternative measures of adiposity to BMI and pregnancy outcomes.
Methods: Ten electronic databases were searched in January 2019, supplemented by citation and reference list searches and contacting authors. Observational studies were included if they reported early pregnancy (<20 weeks) adiposity measures and any pregnancy outcomes. Studies were excluded if they were restricted to specific populations (e.g. women with PCOS), or were focussed on low adiposity/undernutrition. Screening, data extraction and quality assessments were carried out in duplicate. Assessment of suitability for pooling studies for meta-analyses is ongoing.
Results: Searches identified 78 studies that met the inclusion criteria (n=84,962 women). Studies were published between 1995 and 2019, and quality was rated as high (n=44) and medium (n=34). Studies were from Asia (n=25), North America (n=21), Europe (n=19), South/Central America (n=5), Australia (n=4), Africa (n=3) and multi-continent (n=1). Studies predominantly reported early pregnancy waist circumference. Additional adiposity measures reported were: circumferences (arm, thigh, calf, neck, wrist); ratios (waist:hip, waist:height, neck:thigh); skinfolds (tricep, bicep, supra-iliac, subscapular, abdominal); ultrasound (subcutaneous, visceral fat); and bio-impedence (fat/fat free/lean mass). The pregnancy outcome data predominantly related to GDM. Additional outcomes reported include birth weight/fetal growth, pre/post-term birth, pre-eclampsia, caesarean, perinatal death, neonatal ICU admission, and other maternal and perinatal conditions (e.g. anaemia, jaundice). Associations between BMI and pregnancy outcomes were reported by 47 studies which will enable a comparison to be carried out between the use of BMI and alternative measures in early pregnancy.
Conclusions: Synthesis is ongoing. The potential benefits of identifying accurate adiposity risk prediction measures include the development of more targeted and cost effective intervention for those women with increased risk.
12 Sep 2019 - 13 Sep 2019