Obesity and its effect on your pregnancy

Obesity has been described as one of the biggest health challenges of the 21st century, with widespread phenomenon across the world. In Australia obesity is a major problem particularly in obstetric care with direct link between maternal weight and pregnancy outcome. This is of concern with statistics showing 35% of Australian women between 25 and 35 years of age classed as obese and three-fold increase in number of women defined as having class II and III obesity.

Obesity is classed through calculation of one’s body mass index; weight divided by height squared.The World Health Organisation Classification of obesity states:

  • Underweight = BMI <18.5
  • Normal = 18.5 – 24.9
  • Overweight = 25 – 29.9
  • Obese Class I = 30 – 34.9
  • Obese Class II = 35 – 39.9
  • Obese Class III or morbid obese = >40

Maternal obesity is one of the most common risk factors in obstetric practice, and once diagnosed, classifies the pregnancy as a high risk situation. This is due to its associations with serious maternal, antenatal, peripartum and neonatal complications.

Being overweight is one of the most common causes of problems during pregnancy and just this issue alone can mean your pregnancy might be classified as ‘high risk’. Overweight Mums are much more likely to experience complications either during the pregnancy or around the time of birth, leading to difficulties for the newborn.

Pregnancy is affected by obesity in following ways:

1) Preconception

  • More likely to experience difficulties getting pregnant
  • Increased risk of miscarriage – both as a single event or multiple (recurrent miscarriage)

2) Antenatal

  • Unexplained stillbirth – when the baby dies unexpectedly during the pregnancy
  • Higher chance of developing some pregnancy conditions such as high blood pressure, diabetes, gall stones, blood clots in the leg or lung (known as deep vein thrombosis or DVT), which can be life-threatening
  • Greater risk for baby having a developmental abnormality or birth defect
  • Monitoring baby’s growth and development is more difficult and less accurate – both by your midwife or obstetrician and via ultrasound scans
  • A higher chance of baby being born premature (early)
  • Baby may be larger, which can lead to difficulties with the birth

3) Labour

  • Increased difficulty for the anaesthetist when inserted an epidural or spinal  for pain relief due to access, or the epidural might not work as well as it should
  • If you are getting induced, there is a higher chance that labour won’t progress and you may have to have an emergency caesarean section
  • Increased risk of baby getting stuck during labour process
  • A higher chance of having to use a vacuum or forceps to help get baby out
  • Baby may also not be as healthy once delivered and suffer problems such as trouble with breathing, which can mean a few nights in neonatal intensive care unit

4) Postnatal

  • Increased risk of getting an infection at the caesarean wound site
  • Increased risk of developing mastitis
  • There may be problems with incontinence where you lose control of urinating due to pelvic floor muscles becoming weakened
  • Greater risk of the baby being overweight and developing childhood obesity or diabetes

Your weight should ideally be addressed in the preconception period with health care provider taking opportunity to calculate one’s BMI. Women should be encouraged to only enter pregnancy with a BMI of at maximum 30, however ideally less than 25. The BMI calculated in this pre-pregnancy status is the most accurate measurement, through avoiding overestimation.

Pregnancy is a time characterized by substantial weight gain, however one must not assume they should ‘eat for two’ as excess consumption impacts on the health of both mother and baby further. Excess weight gain during pregnancy is also a strong predictor of post-partum weight retention, which contributes further to obesity epidemic. Gestational weight gain must be achieved in a controlled fashion to prevent contribution to the obesity epidemic.

Current recommendations for weight are dependent on BMI and include:

One’s diet should be in accordance with the Australian Guide to Healthy Eating and in addition, pregnant mums should receive nutritional counseling and dietitian input in efforts to address weight issues and avoid complications as previously mentioned.

Provided is a brief summary of these recommendations:

  • Adhere to target weight gain goals
  • Follow recommended food group requirements, as listed below
  • 30 minutes of moderate exercise for at least 4 days of week
  • 50mg folic acid at least 1 month prior to conception and during first trimester
  • Vitamin D supplementation during pregnancy and breastfeeding
  • Encourage breastfeeding, especially given it facilitates weight loss post-partum

Today no evidence-based guidelines exist for obesity women and diet during pregnancy. Controversy also remains as to whether calorie-restricting weight loss diets can play a role in obese pregnant women and is currently under review.

Weight is a modifiable cause of adverse outcomes in pregnancy, thus as both a patient and doctor we must make an active effort to address this issue given the huge impact on delivery of obstetric care.


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