DOI: 10.1111/1471-0528.13758
General obstetrics
www.bjog.org
Maternal abdominal subcutaneous fat thickness as a predictor for adverse pregnancy outcome: a longitudinal cohort study NJ Kennedy,a,b MJ Peek,a,c AE Quinton,a,c,d V Lanzarone,e A Martin,f R Benzie,a,b R Nanana,c a
Discipline of Obstetrics, Gynaecology and Neonatology, Sydney Medical School Nepean, Nepean Hospital, University of Sydney, Penrith, NSW, Australia b Christopher Kohlenberg Department of Perinatal Ultrasound, Nepean Hospital, Penrith, NSW, Australia c Charles Perkins Centre, Nepean, Sydney, Australia d Medical Sonography, School of Medical and Applied Sciences, Central Queensland University, Sydney, Australia e Ultrasound for Women Penrith, Nepean Hospital, Penrith, NSW, Australia f National Health and Medical Research Council (NHMRC) Clinical Trials Centre, University of Sydney, Sydney, Australia Correspondence: N Kennedy, Discipline of Obstetrics, Gynaecology and Neonatology, Sydney Medical School Nepean, University of Sydney, Nepean Hospital Penrith, NSW 2750 Australia. Email
[email protected] Accepted 25 September 2015.
Objective To assess maternal abdominal subcutaneous fat
thickness (SFT) measured by ultrasound as an independent predictor of adverse pregnancy outcomes. Design A prospective longitudinal cohort study performed on
pregnancies delivered between 2012 and 2014. Setting Sydney, Australia. Population About 1510 pregnant women attending routine
obstetric ultrasounds. Methods Maternal SFT was measured on routine ultrasounds at 11–14 weeks’ gestation (SFT1) and 18–22 weeks’ gestation (SFT2). SFT measurements were assessed for estimating risks for obesityrelated pregnancy outcomes using logistic regression modelling adjusted for maternal age, parity, smoking status and body mass index (BMI). Main outcome measures Hypertensive disease, gestational
diabetes, caesarean section, low birthweight, preterm delivery, neonatal respiratory distress, Apgar scores, and admission to a neonatal intensive care unit.
Results SFT1 and SFT2 were measured on 1461 and 1363 women, respectively. Mean thickness (range) were 21.2 mm (6.9– 73.9) for SFT1 and 20.3 mm (7.5–68.0) for SFT2. Complete outcome data were available for 1385 pregnancies. In all, 54% of the women were overweight/obese. The SFT measures decreased from early to mid-pregnancy in overweight/obese women. There was moderate correlation between BMI and SFT1 (R2 = 0.56) and BMI and SFT2 (R2 = 0.55). In a multivariate model, SFT1 and SFT2 were better predictors for adverse pregnancy outcomes than BMI. Conclusion Maternal SFT is a significant independent predictor
of adverse pregnancy outcomes. Incorporation of SFT into future models for adverse pregnancy outcome may prove valuable. Keywords Adipose, adverse pregnancy outcomes, maternal adipose, obesity, pregnancy, subcutaneous fat, ultrasound. Tweetable abstract Maternal abdominal ultrasound fat thickness
measurement predicts adverse pregnancy outcomes.
Please cite this paper as: Kennedy N, Peek MJ, Quinton AE, Lanzarone V, Martin A, Nanan R, Benzie R. Maternal abdominal subcutaneous fat thickness as a predictor for adverse pregnancy outcome: a longitudinal cohort study. BJOG 2016;123:225–232.
Introduction Adipose tissue is a storage area for energy. It also acts as an endocrine and immune organ releasing signals that affect the physiology of the body. Hence, excessive accumulation of adipose tissue gives rise to chronic inflammatory responses and disarranges metabolic homeostasis, resulting in obesityrelated diseases.1,2 Pregnancy in itself is associated with natural inflammatory and metabolic changes, which can be
ª 2015 Royal College of Obstetricians and Gynaecologists
significantly confounded in obese women, leading to specific obesity-related complications.3–6 There is growing prevalence of obesity worldwide; in Australia, 40–50% of the pregnant population is overweight and obese.7,8 This increases related pregnancy complications such as gestational diabetes, pre-eclampsia and fetal growth disorders.4–6 Postnatal complications include neonatal low Apgar score, hypoglycaemia, jaundice, and maternal infection and haemorrhage.9–12
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For practical reasons, body mass index (BMI) is used clinically for risk stratification of obesity-related pregnancy complications. However, BMI does not reflect fat distribution or the proportion of adipose to non-adipose tissue.13,14 The significance of fat distribution is obvious, with central abdominal obesity (adipose tissue around the trunk) increasing the risk of cardiovascular disease, hypertension and diabetes,15–18 whereas peripheral adiposity (adipose tissue around the bottom and thighs) appears to be protective.17,19 Although impractical for pregnancy, central adiposity can be reliably assessed with computed tomography, magnetic resonance imaging or body densitometry. Abdominal subcutaneous fat thickness (SFT) correlates significantly with a range of obesity-related diseases such as diabetes and cardiovascular disease.20–22 Maternal abdominal subcutaneous fat thickness can be used as a surrogate measure for central obesity and is readily and accurately measured by ultrasound, a quick, safe modality used routinely in pregnancy.23–28 From a retrospective study there is some evidence that abdominal SFT at mid-pregnancy between 18 and 22 weeks’ gestation is superior to BMI to identify risk for obesity-related pregnancy complications.29 In this prospective longitudinal study we tested whether previous findings of SFT could be confirmed and in addition whether changing these parameters to early pregnancy between 11 and 14 weeks as well as mid-pregnancy would have additional predictive value.
Methods A prospective study was performed over a 2-year period from 2012 to 2014. Pregnant women were recruited to the study at two departments within a tertiary referral hospital and private ultrasound clinic in Sydney, Australia. The SFT measures were performed by both sonographers and sonologists working in these departments. Informed written consent was obtained before the ultrasound examination was performed. Demographic data was collected about each participant at the initial ultrasound; this included age, height, weight, smoking habit, ethnicity and parity. The SFT measurement was made at the 11–14 weeks’ gestation (SFT1). The women were then asked to return for their routine 18–22 weeks ultrasound where a subsequent measurement was made (SFT2). The SFT measurements were taken at the cervix placenta view.29 This was obtained by placing a standard convex array ultrasound transducer, mid-sagittal and superior to the symphysis pubis, measuring in the midline through the linea alba. Landmarks demonstrated on the ultrasound image were the bladder, cervix and uterus, ensuring that the image contained the skin line and that the tissue in the near field was easily distinguish-
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able. These landmarks provided a guideline to ensure that the measurement of the subcutaneous fat was reproducible. Three measurements were taken to obtain a mean SFT measure. The first measure was done close to the midline and two measures were taken 5 mm on either side to take into account the curvature from the ultrasound transducer face, and ensuring the measurements were done perpendicular to the anterior border. The calipers were placed from the skin line to the peritoneal fascia (Figure S1).
Data collection Data on pregnancies were retrieved using an obstetric database and by accessing medical records. Information on outcomes included pregnancy complications such as pregnancy-induced hypertension (defined as systolic blood pressure of ≥140 mmHg with a diastolic blood pressure of ≥90 mmHg on two separate readings),30 gestational diabetes (diet- and insulin-controlled), preterm labour, premature rupture of membranes and antepartum haemorrhage. Gestational age and mode of delivery were documented, with preterm delivery defined as 90th percentile and small-forgestational-age as
