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Have a look at this diagram - this will give you some revision on the metabolic effects of obesity.  You can see that with obesity there will be dyslipidaemia with rises in triglycerides, LDL - cholesterol, and fall in HDL.  There will also be increases in leptin and fasting insulin. Overall there is a pro-inflammatory state with endothelial dysfunction and vasoconstriction.  All of these can have effects for both the mother and the baby.


(Hutley L, Prins J. Fat as an endocrine organ: Relationship to the metabolic syndrome. Am J Sci. 2005;330(6):280-289)



Activity - What are the effects on the mother and the baby with maternal BMI > 30?

From the metabolic and vascular changes show in the diagram above, the effects of obesity on the mother are evident e.g. high blood pressure and preeclampsia but there are many other effects of obesity for the mother and baby in pregnancy!  Have a think about what these effects may be- jot down your list and then check with our lists below


Click here for the list of maternal effects

The incidence of the following outcomes is increased for obese women during pregnancy: 


  • Miscarriage 
  • Gestational diabetes
  • Preeclampsia 
  • VTE
  • Obstructive sleep apnoea 
  • Preterm birth 
  • Maternal death 


  • Induction of labour, prolonged labour, and failure to progress 
  • Instrumental delivery and failed instrumental delivery 
  • Shoulder dystocia
  • Caesarean section 
  • Difficulties with fetal heart rate monitoring 
  • Difficulties with labour analgesia 
  • PPH 
  • Peripartum death 
  • Anaesthetic risks 


  • Increased need for ICU post-operatively 
  • VTE
  • Delayed wound healing and infection 
  • Greater likelihood of needing support with breastfeeding establishment and continuation 
  • Postnatal depression 

Reference: RANZCOG. 2017. Management of Obesity in Pregnancy. 

Click here for the list of effects on the baby

  • Fetal congenital abnormalities 
  • Preterm birth 
  • Stillbirth 
  • Neonatal death 
  • Abnormalities in fetal growth 
  • Shoulder dystocia 
  • Greater likelihood of the mother needing with suport with breastfeeding establishment and continuation 
  • Long term neonatal consequences: neonatal body composition, infant weight gain, obesity 

Reference: RANZCOG. 2017. Management of Obesity in Pregnancy. 

You can see from this list that the baby is at higher risk of fetal abnormality so it is really important to recommend these mothers take the folic acid supplementation prior to and in the first trimester of pregnancy.  A 5mg supplement is recommended for obese women.

So where do you think Kiwis rate in the world obesity levels? The NZ health survey 2017/2018 found that 32% of New Zealand adults were obese, the third highest rate in the world. 

In 2014, at National Women's hospital, only 55.5% of pregnant women had the ideal body size (BMI 18.5-24.9). 5% were underweight (BMI<19), 30.5% overweight or obese (BMI 26-35), and 8% were morbidly obese (BMI >35).


Click the PDF icon to see a picture showing body images for mature women.   Which of these women has the ideal body weight?

This picture is taken from one of your recommended textbooks:

Section 2. Women and Health in Obstetrics, Gynaecology and Women's Health. Vivienne O'Connor and Gabor Kovacs (Eds) p889. Cambridge University Press


You may need to remind yourself now of how to calculate BMI!  It is very important to measure height and weight and  not take the woman's estimate.

Along with BMI the rates of gestational diabetes have also been steadily increasing at National Women's Hospital. Have a look at the GDM graphic below



So looking at those National Women's statistics, 38% of the women were overweight or obese and in Counties Manukau the rates are about 60% - these figures have major implications for pregnancy complications and health costs. Let's have a further look at these issues now.


Labour and delivery: BMI > 30

From the list of effects that we looked at above we saw that these women are more likely to be induced. There is a 2 to 3 fold increase in failure to progress in labour - an effect that is independent of baby size and pregnancy problems.  One of the outcomes of this is a marked increase in Caesarean section rates for failure to progress which has a huge effect on staff and resources.  Also for the woman there is the added increased risk of morbidity and mortality especially if she should require a general anaesthetic for her section (which is more likely in obese women). If regional anaesthesia is needed, such as epidural, access can be more difficult for women who are larger and often different equipment is needed.


These risks can be decreased if the woman can limit weight increase in pregnancy!

The Institute of Medicine (IOM 2009) recommends that women who have a pre-pregnancy BMI>30 should have 5-9kg weight gain in pregnancy.


So it is really important once BMI is measured at the booking visit that we talk to women about what the goals are for pregnancy weight gain, take a simple dietary history, work out an exercise plan, and to continue to do serial weight measurements during the pregnancy. Sometimes a referral to the dietician for extra support can be helpful however we can all take a dietary history and provide simple advice about healthy easting in pregnancy (see some tips on the Ministry of health pamphlet below).  Babies born to obese mothers are at 4 times the risk of childhood obesity and there are strategies that can also help here.  Aiming to breastfeed exclusively for at least 4 to 6 months is ideal - this may need the help of a lactation consultant.  


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