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Accurate height and weight measurement necessary to reduce risk for pregnant women

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Friday, 11 April 2014 9:24am

mother and child

A study by the University of Otago shows there are inaccuracies being made in the documented height and weight of pregnant women at the time of their 12-week scan, which could change clinical risk assessments for women.

The research found that heights and weights recorded at the time of the scan differed from the women’s actual measurements resulting in 69% of the 248 women who participated having an under-reported BMI, 6% a correctly reported BMI, and 25% an over-reported BMI.

As a result 17% of participants would have been incorrectly classified by BMI category when compared with measured data, according to the study, which appears in this week’s edition of the New Zealand Medical Journal.

Height and weight are important measures for maternity care as they are used to assess risk during pregnancy and labour. Inaccurate height and weight will affect the first trimester combined screening for Down syndrome and other conditions, and could lead to a suboptimal screen.

They are also used in the calculation of customised growth charts which assess the baby’s progress—potentially leading to missed high-risk pregnancies—and in determining the recommended amount of weight gain.

“To improve care we need to ensure that women and lead maternity carers (LMCs) have access to accurate scales that can measure more than the standard 120kg,” says researcher and consultant obstetrician and gynaecologist, Dr Helen Paterson.

“A logical option to improve the first trimester combined screening would be to have calibrated scales available in laboratories where women have their blood samples taken.”

In 2012 the Perinatal and Maternal Mortality Review Committee recommended that all women should be advised on healthy weight gain based on international guidelines to avoid possible complications in pregnancy.

Research shows that excessive weight gain during pregnancy is associated with increased risk of hypertension, gestational diabetes, potentially serious complications during labour, and subsequent maternal and child obesity.

Dr Paterson says: “It’s a concern that along with an increasing problem with excess weight and obesity in New Zealand, we have unreliable height and weight data on which to make clinical decisions.”

The study supports the New Zealand College of Midwives’ recommendation that all women of childbearing age must have their height and weight accurately measured and documented, and BMI calculated at a woman’s first visit, ideally before ten weeks of pregnancy.

This study was funded by the University of Otago.

For further information contact:

Dr Helen Paterson
Department of Women’s and Children’s Health
University of Otago
Tel 64 3 474 0999 ext 8933
Email helen.paterson@otago.ac.nz

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