Weight gain restriction in pregnancy - should we be worried about the baby?

Thanks to ‘Dr Google’, there is a vast array of health and nutrition information at our fingertips, with pregnancy sparking an onslaught of questions (and late night Googling). A woman’s body undergoes vast changes to support the growth and development from what starts as an embryo through to a fully formed baby. Amongst the many physiological and physical changes occurring, a woman’s weight increases during pregnancy. But how much weight gain is considered ‘healthy’? Are there implications for the baby when a woman gains too much or too little weight during pregnancy? And are there longer term health implications into childhood that we need to be aware of?

Discussing weight gain during pregnancy is difficult, but nonetheless important. A woman will gain weight during pregnancy for a number of reasons, these range from an increase in blood volume to, changes in maternal body composition including fat deposition and not to mention the growing infant, amniotic fluid and placenta.

The amount of weight gained during pregnancy has a significant impact on the developing foetus - with excessive gains increasing the risk of ‘large for gestational age’ infants (i.e. >90% percentile) and macrosomia (birth weight >4kg) [1]. If a baby is larger than average it increases the risk of several complications including birth trauma, post-partum haemorrhage and the need for caesarean section [2]. Importantly, these implications don’t end with the infant's birth weight. In the short term, children born to mothers who gained excessive weight during pregnancy are more likely to have concerning vital signs directly after birth which may require medical attention [3]. They are also at a higher risk of developing infections [3] and are more likely to have an increased length of hospital stay at birth [3]. In the long term, children who are born to mothers that experienced excessive weight gain during pregnancy are also are more likely to have higher BMI z-scores as children (this is a measure of relative weight adjusted for child age and gender) [4] and suffer from obesity, diabetes and high blood pressure later in life [5].

Complications also arise where inadequate weight gains occur during pregnancy. Foetal growth can be impaired, increasing the risk of small for gestational age infants (<2.5kg), lower lean body mass, fat mass and head circumference [6]. In the long term, children of mothers who gained inadequate weight during pregnancy may also be at a higher risk of obesity [7], cardiovascular disease [8], breast cancer [7] and glucose intolerance [7] later in life.

International guidelines for weight gain during pregnancy outline that the higher the pre-pregnancy body mass index (BMI) the less weight a woman should gain [9]. In countries such as Australia, the majority of women gain too much weight during pregnancy [10], suggesting that interventions designed to reduce gestational weight gain may have a significant influence on both the mother and the health of the next generation [11].

While many interventions have been trialled in a bid to reduce weight gain during pregnancy [12], their impact on the infant’s birth weight is not clear. Given the risks associated with both high and low birthweight an important question remains – if we reduce the amount of weight a woman gains during pregnancy, does this influence health outcomes for the infant?

A team of researchers from Monash University’s Department of Nutrition, Dietetics and Food and collaborators from Lanzhou University and Zhejiang University in China conducted a recently published meta-analysis on trials conducted across the world to answer this question.

Lead researcher, Ms Christie Bennett, from the Department of Nutrition, Dietetics and Food at Monash University, explained that there were positive implications when excessive weight gain during pregnancy was reduced. Importantly, she explained that these positive outcomes were not associated with increasing the risk of complications such as low birth weight or being categorised as small for gestational age. “This study provides good news for expectant mothers - even a slight reduction in weight gain during pregnancy (i.e. 1 -2 kg) may have the potential to reduce the life-long consequences of high birth weight, potentially influencing the risk of conditions such as obesity, diabetes and cancer in the long-term” explained Christie. Supporting women to gain the right amount of weight during pregnancy is vital and may give the next generation the best start to life.

The team at Monash are looking at innovative ways to reduce the amount of weight woman gain during pregnancy. Currently, their research has two major focuses i) how better to support and train antenatal clinicians to support women during pregnancy and ii) the impact of sleep on gestational weight gain.

In addition to the team's research efforts, the Department is working closely with the medical and health profession through their two online courses: ‘Talking about Weight’ and ‘Food, Fertility and Pregnancy’. You can visit the courses here.

More information:

Ms Christie Bennett is a PhD Scholar and Accredited Practising Dietitian in the Department of Nutrition, Dietetics and Food at Monash University. Her current research focuses on the impact of sleep during pregnancy on nutritional intake, gestational weight gain and obstetric outcomes. Click here to access Christie’s research profile. You can follow Christie on Twitter via @Bennett_CJ1.

Stay up to date with the Monash University Department of Nutrition, Dietetics and Food on Twitter via @MonashNutrition.

Publication information

Reference: Bennett CJ, Walker RE, Blumfield ML, Ma J, Wang F, Wan Y, Gwini SM, Truby H.
Attenuation of maternal weight gain impacts infant birthweight: systematic review
and meta-analysis. J Dev Orig Health Dis. 2018;Nov 9:1-19. doi:
10.1017/S2040174418000879. [Epub ahead of print]

Obesity Reviews is ranked 68 out of 180 in the category of Public, Environmental and Occupational Health and has an impact factor of 2.215.

Link to publication: Click here to access the paper published in the Journal of Developmental Origins of Health and Disease.

Image credit: Rawpixel via Unsplash

References: 

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