Pregnancy Care Guidelines

19 Weight and body mass index

Body mass index (prior to pregnancy or at the first antenatal visit) and weight gain during pregnancy are among the important determinants of the health of both mother and baby.

19.1 Background

19.1.1 Calculating and interpreting BMI 

Body mass index (BMI) is commonly used to classify adults as being underweight, of healthy weight, overweight or obese. It is calculated by dividing weight by the square of height: weight (kg)/height (m)2. The WHO classification of BMI classification is given in Table D1.

Table D1: Classification of adult underweight, overweight and obesity according to BMI

A list of BMIs (noted in kilograms by square metres) and classifications.
BMI (kg/m2) Classification
<18.50 Underweight
18.5–24.9 Healthy weight 
25.0–29.9 Overweight
≥30.0 Obese

19.1.2 Weight classification during pregnancy in Australia

Among women who gave birth in Australia in 2018 (AIHW 2020):

  • 3.8% were underweight, 49.5% were in the healthy weight range, 26.0% were overweight but not obese and 21.0% were obese at the first antenatal visit
  • Aboriginal and Torres Strait Islander women were more likely than non-Indigenous women to be either obese (31.0% vs 21.0%) or underweight (6.8% vs 3.8%) and less likely to be in the healthy weight range (38% vs 49.5%), with a similar likelihood of being overweight but not obese (24%)
  • compared to women in the highest socioeconomic status quintile, those in the most disadvantaged quintile were more likely to be obese (26.7 vs 12.4%), less likely to be in the healthy weight range (42.0 vs 60.3%) and had a similar likelihood of being overweight (27.1 vs 23.1%) or underweight (both 4.2%)
  • obesity was most common in very remote areas (27.1 vs 18.7% in major cities), prevalence of overweight was similar across geographical regions, prevalence of healthy weight decreased with increasing remoteness (51.7% in major cities to 39.2% in very remote areas) and underweight was more common in very remote areas (7.1 vs 3.8% in major cities).

19.1.3 Weight stigma

Determinants of heath, including weight status, involve complex interactions between multi-level factors including policy, community, socio-demographic, psychosocial, family and genetic influences. Awareness of weight stigma can help health professionals to provide care that recognises the complexity of these interacting factors and removes inadvertent blame from the individual for less desirable health outcomes. Among the general population, weight stigma is a recognised risk factor for adverse psychological and physical health issues, which can exacerbate unhealthy eating behaviours (such as binge eating) and weight gain (Yazdizadeh et al 2020).

There is evidence of perceived weight stigma felt by women receiving pregnancy care (regardless of their size) (Bombak et al 2016); (Incollingo Rodriguez et al 2019). This can be tied to the fact that high weight status has been linked to adverse pregnancy outcomes. High gestational weight gain has also been linked to increased vulnerability to weight stigmatisation (Incollingo Rodriguez et al 2019). Evidence from non-pregnant populations highlight the potential for stigma to reinforce an unhealthy weight gain cycle (Tomiyama 2014).

Recommendation

  • Practice point
  • S

Adopting a respectful, positive and supportive approach and providing information about healthy eating and physical activity in an appropriate format may assist discussion of weight. This should be informed by appropriate education for health professionals.

Approved by (NHMRC) in Nov 2020; expires Nov 2025

19.2 Assessing BMI

19.2.1 Measuring height and weight and calculating BMI

Routine measurement of women’s weight and height and calculation of BMI at the first antenatal contact allows identification of women who require additional care during pregnancy. When there is an accurate record of a woman’s pre-pregnancy BMI, this may be used to estimate gestational weight gain (see Section 19.3). Note that the BMI can be less accurate for assessing healthy weight in certain groups due to variations in muscle mass and fat mass (eg cut-offs lower than the WHO classifications may be appropriate for women from Asian backgrounds and higher cut-offs for women from the Pacific Islands).

19.2.2 Risks associated with a low or high BMI

Low pre-pregnancy BMI

Systematic reviews are consistent in finding that low pre-pregnancy BMI is associated with an increased risk of:

  • preterm birth (Han et al 2011); (Liu et al 2016)
  • small for gestational age (Yu et al 2013); (Liu et al 2016); (Goto 2017); (Liu et al 2019)
  • low birthweight (Han et al 2011); (Yu et al 2013); (Liu et al 2016); (Liu et al 2019).

Systematic reviews have also found a possible increase in risk of miscarriage (Balsells et al 2016) and placental abruption (Adane et al 2019) and a decreased risk of gestational diabetes (Torloni et al 2009). There was no clear effect on risk of congenital heart defects (Zhu et al 2018).

High pre-pregnancy BMI

Systematic reviews are consistent in finding that pre-pregnancy overweight and obesity is associated with:

  • large for gestational age (Yu et al 2013); (Liu et al 2016); (Liu et al 2019)
  • macrosomia (Yu et al 2013); (Liu et al 2016); (Liu et al 2019)
  • childhood overweight/obesity (Yu et al 2013); (Voerman et al 2019).

Systematic reviews have also found associations between high pre-pregnancy BMI and:

  • increased risk of gestational diabetes (Torloni et al 2009), preterm birth, neonatal asphyxia (Liu et al 2019), admission to neonatal intensive care, stillbirth (Liu et al 2016) and congenital heart defects (Cai et al 2014); (Zhu et al 2018)
  • reduced risk of small for gestational age (Goto 2017) and placental abruption (Adane et al 2019).

Systematic reviews found a decreased likelihood of initiating breastfeeding among women who were obese (Garcia et al 2016); (Huang et al 2019).

19.2.3 Discussing BMI with women

Women who have a BMI that is below or above the healthy range are likely to require additional care and support during pregnancy. For women with an elevated BMI, there may be additional implications for care during pregnancy (eg the potential for difficulties with palpation and poor ultrasound visualisation) and the birth (eg need for the birth to take place in a larger centre, difficulties with fetal assessment and monitoring). Relevant risks associated with a woman’s BMI should be explained and the woman given the opportunity to discuss these and how they might be minimised.

Assessment of fetal growth is discussed in Section 22.1 and assessment for risk of preterm birth in Chapter 23.

19.3 Monitoring weight gain

While BMI prior to or early in pregnancy is independently associated with pregnancy outcomes, the amount of weight gained during pregnancy is also a contributing factor. The US Institute of Medicine (IOM) provides guidance on weight gain in pregnancy based on pre-pregnancy BMI. The IOM recommendations are consensus-based and were written in 2009 but have since been assessed using data from 1.3 million women (Goldstein et al 2017a).

Table D2: IOM recommendations for weight gain in pregnancy

A list of IOM recommendations with 3 columns: Pre-pregnancy BMI (kg/m2), weight gain (kg) and Rates of weight gain 2nd and 3rd trimester (kg/wk).
Pre-pregnancy BMI (kg/m2) Recommended weight gain (kg) Rates of weight gain 2nd and 3rd trimester (kg/wk)
<18.5 12.5–18.0 0.51 (0.44–0.58)
18.5 to 24.9 11.5–16.0 0.42 (0.35–0.50)
25.0 to 29.9 7.0–11.5 0.28 (0.23–0.33)
≥30 5.0–9.0 0.22 (0.17–0.27)
  • * Calculations assume a 0.5–2kg weight gain in the first trimester.
  • Note: The recommended weight gain ranges are indicative only and provide suggested limits rather than specific goals.
  • Sources: (NHMRC 2013) based on (IOM 2009).
  • Source: (NHMRC 2013) based on (IOM 2009).

A number of studies have suggested that the IOM guidelines may not be applicable to all women.

  • A systematic review of the utility of IOM-2009 guidelines among Indian and other Asian pregnant women in terms of maternal and fetal outcomes (n=13 studies) (Arora & Tamber Aeri 2019) highlighted the need for gestational weight gain recommendations across the different body mass index levels specifically for Indian women and other Asian populations.
  • A retrospective cohort study in China (n=8,209) (Jiang et al 2019) found that the lowest accumulated risk of low birthweight and macrosomia was not always achieved among women who gained weight within recommendations and suggested that the IOM weight gain ranges are too high for Chinese women.
  • A cohort study in the United States (n=181,948) (Khanolkar et al 2020) found that adherence to the 2009 IOM guidelines for weight gain during pregnancy reduced risk for various adverse maternal outcomes in all ethnic groups studied. However, the guidelines were better at predicting small and large for gestational age than other infant outcomes.

Table D3: Recommendations for weight gain in pregnancy among women from an Asian background

Pre-pregnancy BMI (kg/m2)

Recommended weight gain (kg)

Rates of weight gain* 2nd and 3rd trimester (kg/wk)

<18.5

12.5–18.0

0.5

18.5–22.9

11.5–16.0

0.4

23–27.5

7.0–11.5

0.3

>27.5

≤ 7.0

  • Sources: (NHMRC 2013) based on (IOM 2009) and matched with Asian BMI cut-offs .

Recommendation

  • Consensus-based
  • XI

With women’s consent, measure their weight and height at the first antenatal visit, calculate their pre-pregnancy body mass index (BMI) and give them advice about the benefits of meeting the recommended healthy weight gain for their pre-pregnancy BMI.

Approved by (NHMRC) in Nov 2020; expires Nov 2025

19.3.1 Determinants of gestational weight gain

Weight gain below guidelines

A systematic review found that women with lower educational attainment had an increased risk of inadequate weight gain (OR 1.3; 95% CI 1.0 to 1.6, p=0.017) (O'Brien et al 2019).

An analysis of observational data from a longitudinal cohort study of Aboriginal women during pregnancy (n=110)(Schumacher et al 2018) found that 32% of women had inadequate weight gain.

Cohort studies in the United States (Mendez et al 2014); (Headen et al 2015); (Mendez et al 2016) have found that African American women, Hispanic women and women in socially disadvantaged areas are more likely to experience inadequate weight gain.

Weight gain exceeding guidelines

Systematic reviews have found associations between weight gain exceeding recommendations and:

  • lower educational attainment (O'Brien et al 2019)
  • body image dissatisfaction (Hartley et al 2015); (Kapadia et al 2015a)
  • lack of social support (Hartley et al 2015)
  • concern about weight gain, negative attitude towards weight gain, inaccurate perceptions regarding weight, higher than recommended target weight gain, less knowledge about weight gain, higher levels of cognitive dietary restraint, and perceived barriers to healthy eating (Kapadia et al 2015a).

There were no clear associations between weight gain exceeding recommendations and:

  • anxiety (Hartley et al 2015); (Kapadia et al 2015a), stress (Hartley et al 2015); (Kapadia et al 2015a), self-efficacy (Hartley et al 2015), self-esteem (Hartley et al 2015) or social support (Ratan et al 2020)
  • parity (r 0.04, 95%CI 0.10 to 0.16, p=0.61; 17 studies), including after adjusting for pre-pregnancy BMI (r 0.08, 95%CI 0.19 to 0.03, p=0.16; 16 studies) (Hill et al 2017)

The evidence of an association between weight gain exceeding recommendations and depression was inconsistent (Hartley et al 2015); (Kapadia et al 2015a).

Protective factors included a perception of control over weight gain, lower than recommended target weight gain and higher self-efficacy for healthy eating (Kapadia et al 2015a).

Cohort studies have found associations between weight gain exceeding guidelines and:

  • pre-pregnancy BMI (≥25 vs <25) (OR 3.35; 95%CI 2.44 to 4.64; p<0.0001) (Morisset et al 2017)
  • stopping smoking compared to women who never smoked (weekly weight gain in second and third trimesters MD 0.09 kg; 95%CI 0.03 to 0.15) (Hulman et al 2016)

There was no clear association in cohort studies between weight gain exceeding guidelines and:

  • experiencing hardship in childhood (OR 1.45, 95%CI 0.99 to 2.14), in adulthood (OR 0.72; 95%CI 0.41 to 1.26) or in pregnancy (OR 1.09; 95%CI 0.43 to 2.76) (Provenzano et al 2015)
  • maternal age (<30 vs ≥30) (OR 1.02; 95%CI 0.98 to 1.02; p=0.89) (Morisset et al 2017)
  • household income (<CAN$60,000 vs ≥CAN$60,000) (OR 1.06; 95%CI 0.71 to 1.26; p=0.71) (Morisset et al 2017)
  • education level (<university vs ≥university degree) (OR 1.26; 95%CI 0.93 to 1.70; p=0.14)(Morisset et al 2017)
  • country of birth (other countries vs Canada) (OR 1.05; 95%CI 0.78 to 1.41; p=0.73).(Morisset et al 2017).

An analysis of observational data collected from a longitudinal cohort study of Aboriginal women during pregnancy (n=110) (Schumacher et al 2018) found that 54% of women had weight gain exceeding recommendations.

19.3.2 Risks associated with low or high gestational weight gain

A meta-analysis of individual participant data (n=265,270) (Santos et al 2019) found that low or high gestational weight gain was associated with pregnancy complications across all BMI classifications.

Weight gain among women of any BMI

Weight gain lower than recommendations

In a systematic review of cohort studies of pregnant women of any BMI (23 studies; 1,309,136 women) (Goldstein et al 2017b), weight gain lower than recommendations was associated with an increased risk of:

  • preterm birth (OR 1.70; 95%CI 1.32 to 2.20)
  • small for gestational age babies (OR 1.53; 95% CI 1.44 to 1.64).

There was an association between weight gain lower than recommendations and a lower likelihood of:

  • large-for-gestational-age babies (OR 0.59; 95%CI 0.55 to 0.64)
  • macrosomia (OR 0.60; 95%CI 0.52 to 0.68).

There was an association between weight gain lower than recommendations and a possible lower likelihood of caesarean section (OR 0.98; 95%CI 0.96 to 1.02).

In an analysis of individual participant data from the control arms of 36 RCTs (n=4,429) (Rogozinska et al 2019) the odds of preterm birth (aOR 1.94; 95%CI 1.31 to 2.28) and small-for-gestational-age babies (aOR 1.52; 95%CI 1.18 to 1.96) were increased with gestational weight gain lower than recommendations. Findings on caesarean section and large-for-gestational-age babies were inconclusive.

Weight gain higher than recommendations

The systematic review of cohort studies (Goldstein et al 2017b) found that weight gain higher than recommendations was associated with an increased risk of:

  • large-for-gestational age babies (OR 1.85; 95%CI 1.76 to 1.95)
  • macrosomia (OR 1.95; 95%CI 1.79 to 2.11)
  • caesarean section (OR 1.30; 95%CI 1.25 to 1.35).

There was an association between weight gain higher than recommendations and lower likelihood of small-for-gestational-age babies (OR 0.66; 95%CI 0.63 to 0.69) and preterm birth (OR 0.77; 95%CI 0.69 to 0.86).

The analysis of individual participant data from the control arms of RCTs (Rogozinska et al 2019) found that weight gain higher than recommendations was associated with increased odds of caesarean section (aOR 1.50; 95%CI 1.25 to 1.80), large-for-gestational-age babies (aOR 2.00; 95%CI 1.58 to 2.54), and reduced odds of small-for-gestational-age babies (aOR 0.66; 0.50 to 0.87). No significant effect on preterm birth was detected.

A meta-analysis of individual participant data (37 studies, 162,129 mothers and children) (Voerman et al 2019) found that, relative to the effect of maternal pre-pregnancy BMI, excessive gestational weight gain only slightly increased the risk of childhood overweight/obesity within each clinical BMI category (p-values for interactions of maternal BMI with gestational weight gain: p=0.038, p<0.001, and p=0.637 in early, mid, and late childhood, respectively).

Systematic reviews of cohort studies have found that:

  • the risk of urinary incontinence increased with each 10 kg of weight gain (RR 1.34; 95%CI 1.11 to 1.62) (Aune et al 2019)
  • weight gain exceeding recommendations may increase the risk of autism spectrum disorder (OR 1.23; 95%CI 1.09 to 1.38; p=0.0008) but more studies are needed to confirm this result (Tian et al 2019).
High weight gain in early pregnancy

A secondary analysis of an RCT (n=7,895) (Carreno et al 2012) found that among women who gained weight exceeding the IOM guidelines by week 15-18, 93% exceeded the recommended total gestational weight gain. In contrast, 55% of women with early gestational weight gain within recommendations had total gestational weight gain higher than recommendations (p<0.001). Women with excessive early gestational weight gain had higher rates of gestational diabetes (OR 1.4; 95%CI 1.1 to 1.9), large-for-gestational-age babies (OR 1.4; 95%CI 1.2 to 1.6), and macrosomia >4,000 g (OR 1.5; 95%CI 1.3 to 1.8).

Outcomes among women from US/Europe and Asia

Weight gain lower than recommended was associated with preterm birth among women from the USA/Europe (OR 1.35; 95%CI 1.17 to 1.56) but not women from Asia (OR 1.06; 95%CI 0.78 to 1.44) (Goldstein et al 2018). It was associated with an increase in risk of small-for-gestational-age babies among women from both groups.

Weight gain higher than recommended was associated with large-for-gestational age babies, macrosomia and caesarean section among women from both groups.

Gestational weight gain among underweight women

A meta-analysis of individual participant data (n=265,270) (Santos et al 2019) found that among underweight women:

  • low weight gain was associated with an increased risk of preterm birth and small for gestational age (both p<0.001) and a reduced risk of gestational hypertension (p<0.05) and large for gestational age (p<0.001)
  • high weight gain was associated with a reduced risk of small for gestational age (p<0.05).

Gestational weight gain among women with healthy pre-pregnancy weight

In the meta-analysis of individual participant data (n=265,270) (Santos et al 2019), among women with pre-pregnancy BMI in the healthy range:

  • low weight gain was associated with an increased risk of preterm birth and small for gestational age and a reduced risk of large for gestational age (all p<0.001)
  • high weight gain was associated with an increased risk of gestational diabetes, gestational hypertension, pre-eclampsia, preterm birth and large for gestational age and a reduced risk of small-for-gestational age (all p<0.001).

Gestational weight gain among pregnant women who are overweight

In the meta-analysis of individual participant data (n=265,270) (Santos et al 2019), among women who were overweight:

  • low weight gain was associated gestational diabetes, gestational hypertension, pre-eclampsia, small for gestational age (all p<0.001) and preterm birth (p<0.05)
  • high weight gain was associated with gestational diabetes, gestational hypertension, pre-eclampsia, preterm birth and large for gestational age (all p<0.001).

Gestational weight gain among pregnant women with obesity

In the meta-analysis of individual participant data (n=265,270) (Santos et al 2019), among women with obesity both low and high weight gain were associated with increased risk of gestational diabetes, gestational hypertension, pre-eclampsia, preterm birth and large for gestational age (all p<0.001).

Weight gain lower than recommendations

A retrospective cohort study in the United States (n=~12,000,000 birth records) (Thompson & Thompson 2019) found that weight gain lower than the IOM guidelines among women with obesity reduced the risk of gestational hypertension, eclampsia, induction of labour and Caesarean section but was also associated with increased risks for multiple adverse neonatal outcomes with macrosomia the exception.

A systematic review of cohort studies of pregnant women with obesity (18 cohort studies; 99,723 women) (Kapadia et al 2015b) found that weight gain lower than recommendations was associated with an increase in risk of:

  • preterm birth (aOR 1.46; 95%CI 1.07 to 2.00)
  • small-for-gestational-age babies (OR 1.24; 95%CI 1.13 to 1.36).

Weight gain lower than recommendations was associated with a lower likelihood of:

  • large-for-gestational-age babies (aOR 0.77; 95%CI 0.73 to 0.81)
  • macrosomia (aOR 0.64; 95%CI 0.54 to 0.77)
  • gestational hypertension (aOR, 0.70; 95%CI 0.53 to 0.93)
  • pre-eclampsia (aOR 0.90; 95%CI 0.82 to 0.99).
  • caesarean section (aOR 0.87; 95%CI 0.82 to 0.92).

There was no difference in risk of gestational diabetes (aOR 1.15; 95%CI 0.91 to 1.45), low birthweight (aOR1.08; 95%CI 0.76 to 1.54), Apgar score <7 at 5 minutes (aOR 0.92; 95%CI 0.67 to 1.27) or postpartum weight retention (MD -5.3 kg; 95%CI -9.0 to 1.17).

Weight loss

A systematic review of cohort studies (n=60,913) (Kapadia et al 2015c) found that, among women who were obese, gestational weight loss compared to weight gain within the guidelines:

  • increased the risk of small-for-gestational-age babies (aOR 1.76; 95%CI 1.45 to 2.14; 2 studies) and low birthweight (aOR 1.68; 95%CI 1.10 to 2.57; 1 study)
  • was associated with a lower likelihood of large for gestational age (aOR 0.57; 95%CI 0.52 to 0.62; 2 studies), macrosomia (aOR 0.58; 95%CI 0.38 to 0.89; 1 study) and caesarean section (aOR 0.73; 95%CI 0.67 to 0.80; 2 studies).

There was a possible reduction in risk of pre-eclampsia (aOR 0.82; 95%CI 0.66 to 1.02; 1 study) and no clear difference in risk of gestational diabetes (aOR 0.88; 95%CI 0.62 to 1.25; 1 study) or Apgar score <7 at 5 minutes (aOR 1.08; 95%CI 0.81 to 1.44; 2 studies). No studies reported on preterm birth.

Recommendation

  • Consensus-based
  • XII

At every antenatal visit, offer women the opportunity to be weighed so that low or high gestational weight gain is identified and risk of associated adverse outcomes monitored.

Approved by (NHMRC) in Nov 2020; expires Nov 2025

19.3.3 Women’s views on advice on weight gain during pregnancy

A systematic review of qualitative studies (Vanstone et al 2017) found that women are highly motivated to change their behaviour to improve fetal health but may not recognise the link between excess gestational weight gain and negative fetal health outcomes. Regular, clear, sensitive counselling geared to individual circumstances was frequently mentioned as a strong facilitator of healthy weight gain in pregnancy.

An Australian cross-sectional study (n=536) (Hill et al 2019) found that only half of pregnant women were aware of IOM recommendations on gestational weight gain.

Cross-sectional studies from overseas have found that:

  • more than half (57%) of women reported that their healthcare provider talked to them about personal weight gain limits during pregnancy and a third of these women were counselled regularly; among those not counselled, over half (56%) reported that healthcare provider guidance would have been helpful to achieve their target weight (Weeks et al 2020)
  • two-thirds (67%) of women received advice on gestational weight gain as part of antenatal care and women who reported following this advice had lower odds of weight gain exceeding recommendations (OR 0.18; 95%CI 0.03 to 0.91) (n=91) (Lopez-Cepero et al 2018)
  • experiences of regular weighing were positive and participants believed it should be part of standard antenatal care, that there was a lack of information provided on gestational weight gain and healthy lifestyle in pregnancy, and that healthcare professionals are ideally placed to provide this advice (n=10) (Allen-Walker et al 2017). An Australian focus group that examined barriers and enablers to the regular weighing of women throughout pregnancy (n=44) (Hasted et al 2016) found that, while most health professionals supported regular weighing, various concerns were raised. These included access to resources and staff, the ability to provide appropriate counselling and evidence-based interventions, and the impact of weighing on women and the therapeutic relationship.

19.3.4 Health professional’s views on weight monitoring as part of pregnancy care

In an Australian study following introduction of a pregnancy weight gain chart (n=42) (de Jersey et al 2019), 63% of health professionals surveyed used the chart, 76% reported that they needed more training in counselling pregnant women about weight gain, and insufficient time was the main barrier to weighing and discussing weight gain with women.

An Australian cohort study found that recording of weight is improved by providing scales to clinics and staff training (18.9%) and medical record prompts (61.8%) (n=~13,000 per cohort) (Wilkinson et al 2019).

A cohort study in the United States (n=733) (Lindberg & Anderson 2014) found that introduction of a "best practice alert" into an electronic medical record system improved the rate of gestational weight counselling (p<0.001), documented weight gain (p<0.001) and weight gain consistent with guidelines (p=0.003).

19.3.5 Recent evidence on regular weighing

A systematic literature review found no clear difference in weekly weight gain (MD -0.00 kg; 95%CI -0.03 to 0.02) or weight gain exceeding the IOM guidelines for women who were underweight (OR 1.50; 95%CI 0.14 to 16.54), in the healthy weight range (OR 0.72; 95%CI 0.48 to 1.09), overweight (OR 0.85; 95%CI 0.45 to 1.62) or obese (OR 1.60; 95%CI 0.72 to 3.54) (Fealy et al 2017). The interventions assessed in the two included studies (n=977) differed in that one involved regular weighing by a health professional (Brownfoot et al 2016a) and the other involved self-weighing (Jeffries et al 2009).

The systematic literature review conducted to inform these Guidelines (Ramson et al 2020) focused on weighing by a health professional and included three studies.

An Australian RCT (n=782) (Brownfoot et al 2016b); (Brownfoot et al 2016a) addressed regular weighing at antenatal care visits plus advice on weight gain versus usual care. The study found no difference in weight gain, proportion of women gaining more weight than IOM recommended range or secondary outcomes (Brownfoot et al 2016a). Among a subset of women who provided feedback (n=586), 73% were comfortable with being weighed routinely (Brownfoot et al 2016b).

A pilot study in the United Kingdom (n=76) (Daley et al 2015) combined regular weighing by midwives and advice on weight gain with self-weighing between antenatal visits. Compared to usual care, there was no difference in the percentage of women gaining excessive weight during pregnancy or in mean depression and anxiety scores. Feedback in a subset of participants showed support for routine weighing among participants (9/12) and midwives (7/7). The same group then conducted a larger study of the intervention (n=656) (Daley et al 2019), which also found no clear difference in weight gain exceeding IOM guidelines, depression or anxiety.

When these three trials were pooled, there was no difference in weight gain exceeding guidelines (RR 1.01 95% CI 0.92 to 1.12; 3 RCTs; n=1,327; very low certainty) or mean weekly weight gain (MD 0.01 kg per week 95%CI –0.03 to 0.05; 2 RCTs; n=711; very low certainty). When the two United Kingdom studies were pooled, there was a small reduction in the risk of depression (MD -0.77; 95%CI -1.44 to -0.09; low certainty) and anxiety (MD -0.77; 95%CI -1.48 to ‑0.06; low certainty). There was no indication in the three trials that either excessive gestational weight gain or mean gestational weight gain differed in women in the healthy weight range at the beginning of pregnancy compared with women who were overweight or obese.

19.3.6 Other considerations include

  • The potential for sub-optimal visualisation on ultrasound for women with elevated BMI (delaying the ultrasound until 20 to 22 weeks pregnancy for women with BMI ≥30 may provide better results but needs to be balanced against the possibility of a delayed diagnosis of structural anomalies) (SOGC 2010).
  • Antenatal consultation with an obstetric anaesthetist to identify any potential difficulties with venous access, regional or general anaesthesia for women with a BMI ≥40.
  • For women with a high BMI, ongoing nutritional advice following childbirth from an appropriate health professional, with a view to weight reduction and maintenance.

19.4 Practice summary: weight and BMI

When

At all antenatal visits.

Who

Midwife; GP; obstetrician; Aboriginal and Torres Strait Islander Health Practitioner, Aboriginal and Torres Strait Islander Health Worker; multicultural health worker

What

  • Explain the purpose of assessing weight and weight gain during pregnancyDiscuss the benefits of having weight within the healthy range before, during and in between pregnancies. For women with a BMI outside the healthy range, explain that assessing weight gain during pregnancy is helpful in identifying women whose weight gain is below or above recommendations.
  • Engage women in discussions about weight gainOffer women the opportunity to be weighed and to discuss their weight gain since the last antenatal visit. Use the IOM recommendations to give women advice about the risks of inadequate or excessive weight gain. Provide advice on nutrition and exercise based on the Australian dietary and physical activity guidelines (see Chapter 11).
  • Consider referralWomen with a BMI above or below the healthy range or who are gaining weight at a rate below or above recommendations may benefit from referral for nutrition advice from an accredited practising dietitian.
  • Take a holistic approach
    Provide women with culturally appropriate advice on the benefits of a healthy diet and regular physical activity. When making referrals, consider access to and costs of care and develop alternative care pathways for women who experience health inequalities as a result of social and cultural barriers.

19.5 Resources

19.5.1 Health professionals

19.5.2 Women and families

References

  • Adane AA, Shepherd CCJ, Lim FJ et al (2019) The impact of pre-pregnancy body mass index and gestational weight gain on placental abruption risk: a systematic review and meta-analysis. Arch Gynecol Obstet 300(5): 1201-10.
  • AIHW (2020) Australia’s mothers and babies 2018: in brief. Canberra: Australian Institute of Health and Welfare.
  • Allen-Walker V, Mullaney L, Turner MJ et al (2017) How do women feel about being weighed during pregnancy? A qualitative exploration of the opinions and experiences of postnatal women. Midwifery 49: 95-101.
  • Arora P & Tamber Aeri B (2019) Gestational weight gain among healthy pregnant women from Asia in Comparison with Institute of Medicine (IOM) Guidelines-2009: A systematic review. J Pregnancy 2019: 3849596.
  • Aune D, Mahamat-Saleh Y, Norat T et al (2019) Body mass index, abdominal fatness, weight gain and the risk of urinary incontinence: a systematic review and dose-response meta-analysis of prospective studies. BJOG 126(12): 1424-33.
  • Balsells M, Garcia-Patterson A, Corcoy R (2016) Systematic review and meta-analysis on the association of prepregnancy underweight and miscarriage. Eur J Obstet Gynecol Reprod Biol 207: 73-79.
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  • 16 Data from Victoria, Queensland, Western Australia, South Australia, Tasmania and the Australian Capital Territory.
Last updated: 
5 February 2021

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