Obesity in Pregnancy


Published: 07 April 2021

In pregnancy, the challenges of being overweight can easily become magnified, placing both mothers and their babies at increased risk of perinatal morbidity and mortality.

Excessive Gestational Weight Gain

It’s well known that women entering pregnancy with a high body mass index (BMI) are at increased risk of excessive gestational weight gain (GWG) and postpartum weight retention. However, what is less well-known is the associated risk of childhood obesity in children born to women with excessive GWG (McDowell et al. 2018).

GWG doesn’t just include fat but also water, protein and minerals that are deposited into the placenta, fetus, uterus, amniotic fluid, mammary glands, blood and adipose tissue (Olander, Hill & Skouteris 2021). Collectively, all of these components cause GWG to vary considerably between patients. (Olander, Hill & Skouteris 2021).

Recommended amounts of GWG generally depend on the patient’s pre-pregnancy weight:

Pre-pregnancy BMI Recommended GWG (over the whole pregnancy)
Below 18.5 12.5kg to 18kg
18.5 to 24.9

(18.5 to 22.9 if Asian)
11.5kg to 16kg
25 to 29.9

(23 to 27.5 if Asian)
7kg to 11.5kg
Over 30

(over 27.5 if Asian)
5kg to 9kg

(less than 7kg if Asian)

(Adapted from DoH 2021)

Note: The goal of weight management during pregnancy should be to limit GWG rather than lose weight. Weight loss programs are generally inappropriate for pregnant women (Better Safer Care 2021).

With all of these variables, it vital that weight gain in pregnancy is assessed overall and that any advice about weight loss is tailored specifically to each individual patient’s needs.

obesity in pregnancy gestational weight gain assessment

Risk Factors for Excessive Gestational Weight Gain

As Denison et al. (2018) highlight, obesity is rapidly becoming one of the most common obstetric risk factors.

In Australia, about 21% of the antenatal population is classified as obese, with less than half of all pregnant women (49.5%) having a BMI within the normal range (DoH 2021).

There is consistent evidence that the following risk factors can predispose a woman to excessive GWG:

  • Being a younger age
  • Living with pre-pregnancy obesity
  • Living in a deprived community
  • Having a low income
  • High total energy intake
  • High consumption of fried food and dairy
  • Negative body image
  • Low self-efficacy
  • Having an inaccurate perception of their weight.

(Olander, Hill and Skouteris 2021)

Assessing the Risks of Obesity in Pregnancy

Not only are overweight and obese women at greater risk of complications during their pregnancy - but they also use more healthcare resources, spend longer in hospital and incur greater care costs than women with a healthy BMI (Sui, Grivell and Dodd 2012). This can be explained, at least in part, by the increasing incidence of maternal and neonatal complications related to obesity.

In assessing the risks of excessive GWG, Olander, Hill and Skouteris (2021) suggest that both short-term and long-term risks for the mother and baby should be taken into consideration.

Better Safer Care Victoria (2021) has identified a variety of potential complications associated with pregnancy in patients with a BMI of over 30. These include:

Maternal complications Anaesthetic complications Fetal and neonatal complications
  • Increased likelihood of multiple pregnancy
  • Caesarean section
  • Chest, genital tract or urinary infection
  • Cholecystitis
  • Depression
  • Diabetes (gestational or type II)
  • Difficulty gaining surgical access
  • Unsuccessful vaginal birth attempts following a caesarean section
  • Unsuccessful induction of labour
  • Gestational hypertension
  • Haemorrhage
  • Obstructed labour
  • Obstructive sleep apnoea
  • Operative and complicated vaginal birth
  • Pre-eclampsia
  • Preterm birth
  • Reduced breastfeeding
  • Surgical site infection
  • Thromboembolic disease
  • Induction of labour for prolonged pregnancy
  • Death
  • Difficulty intubating
  • Difficulty maintaining an adequate airway
  • Difficulty gaining intravenous access
  • Regional anaesthetic more difficult to site
  • Positioning difficulties
  • Difficulty monitoring blood pressure
  • A decreased success of epidural analgesia during labour
  • Increased risk of regurgitation and aspiration of stomach contents
  • Unpredictable spread of local anaesthetic
  • Increased need for postpartum intensive care unit/high dependency unit admission
  • Suboptimal ultrasonography
  • Increased risk of failure of non-invasive prenatal testing
  • Low Apgar score
  • Admission to neonatal ICU
  • Congenital malformations (e.g. neural tube defects, congenital heart disease, omphalocele, cleft lip and palate)
  • Abnormally large neonate
  • Shoulder dystocia
  • Stillbirth
  • Suboptimal electronic fetal monitoring

(Adapted from Better Safer Care 2021)

Longer-term risks of excessive GWG include:

  • Increased risk of weight gain and obesity in the future
  • A higher risk of both short and long-term obesity in children born to obese mothers.

(Olander, Hill and Skouteris 2021)

Optimising Weight Gain

With all the associated challenges of excessive weight gain in pregnancy, the question is: should weight loss advice and support be provided to obese women of childbearing age who wish to become pregnant?

Denison et al. (2018) are clear advocates of pre-pregnancy weight loss, arguing that both weight and BMI should be measured to encourage women to optimise their weight before conception.

Once pregnant, however, how often should maternal weight gain be monitored, if at all? Traditionally, all pregnant women have their weight and height measured and their BMI calculated at their first antenatal booking visit. However, weight gain is seldom monitored after that, with more focus placed on healthy eating during pregnancy rather than on prescribed weight gain targets.

Is Antenatal Exercise of Value?

According to Better Safer Care Victoria (2021), pregnant patients should be encouraged to perform 30 to 60 minutes of moderate-intensity exercise at least three to four times every week (unless they are experiencing obstetric or medical complications).

Suggested exercises include:

  • Walking
  • Aerobic exercises
  • Stationary cycling
  • Stretching exercises
  • Dancing
  • Hydrotherapy or water aerobics
  • Resistance exercises (e.g. weights or elastic bands).

(Better Safer Care 2021)

Please note that this is not an exhaustive list.

obesity in pregnancy exercise

Professional Support

For many midwives, the greatest challenge is how to approach the topic of weight control during pregnancy. For example, a recent study conducted by Olander, Hill and Skouteris (2021) revealed that health care professionals generally don’t feel confident or knowledgeable enough to provide support regarding GWG. As well as lack of knowledge, other factors preventing healthcare professionals from discussing weight gain included:

  • Lack of time and resources (e.g. weight loss services to refer patients to)
  • Weight gain not being prioritised
  • Concerns about stigmatising patients
  • Concerns about the effectiveness of conversations surrounding GWG.

These concerns are strengthened by the fact that there seems to be very little association between the advice given to women and their overall pregnancy weight gain (Olander, Hill and Skouteris 2021).

In a survey conducted by the Royal College of Midwives (2021), almost half (43%) of midwives surveyed said they lacked confidence about advising women on weight management during pregnancy. Similarly, about 40% said they were worried about asking patients to be weighed other than during their first appointment, with nearly two-thirds of those surveyed expressing concern that they may cause offence by raising the issue of obesity.


Obesity is on the rise globally and being overweight in pregnancy is linked to a range of adverse pregnancy outcomes as well as other long-term health issues.

Assessing GWG, therefore, should be an important part of routine antenatal care in order to reduce the risk of maternal and neonatal complications (Better Safer Care 2021).

Additional Resources



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Anne Watkins View profile
Anne is a freelance lecturer and medical writer at Mind Body Ink. She is a former midwife and nurse teacher with over 25 years’ experience working in the fields of healthcare, stress management and medical hypnosis. Her background includes working as a hospital midwife, Critical Care nurse, lecturer in Neonatal Intensive Care, and as a Clinical Nurse Specialist for a company making life support equipment. Anne has also studied many forms of complementary medicine and has extensive experience in the field of clinical hypnosis. She has a special interest in integrating complementary medicine into conventional healthcare settings and is currently an Associate Tutor, lecturing in Health Coaching and Medical Hypnosis at Exeter University in the UK. As a former Midwife, Anne has a natural passion for writing about fertility, pregnancy, birthing and baby care. Her recent publications include The Health Factor, Coach Yourself To Better Health and Positive Thinking For Kids. You can read more about her work at www.MindBodyInk.com.