Causes and Risk Factors - a quick look

quick look preemiehelp

Although the cause of preterm birth is often unknown, expectant parents need not leave it purely to chance. There are a number of things a potential or expectant mother should and should NOT do, to limit the chances of preterm birth.


Healthy mother, healthy baby

The cause/s of preterm birth may be due to a number of very different events or triggers. Although there are a lot of risks identified there are no good predictors of preterm birth. This section is intended to give you a guide and a better understanding of the risks, some of which are easier to avoid than others depending on your personal circumstances.
Preemie help is here to help you identify any factors you may be able to avoid.


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Obesity and Pregnancy

Societal expectations and media pressure has seen a rise in many women feeling uncomfortable and self-conscious about their body’s; being pregnant can intensify feelings of stress and concern, as the body is going through all sorts of hormonal changes as well as increasing in weight.

Note:if this information, about obesity during pregnancy, causes you any distress you should contact your doctor or midwife about support or counselling.

The following information is of a general nature only and should not be substituted for medical advice or used to alter medical therapy. It does not replace consultations with qualified healthcare professionals to meet your individual medical needs

Main areas covered in this article:

Obesity & Preterm Birth

There is a risk for any woman that things can go wrong during a pregnancy even though most progress without complication. What is important to understand is that obesity increases the risk of having a number of pregnancy complications. In fact the more obese you are the greater the risk. Some of these complications also increase the risk of having a preterm birth.

Obesity may indirectly increase a mother’s risk of preterm birth, as obese mothers are at higher risk for;

  • Gestational diabetes - A form of diabetes that is diagnosed when higher than normal blood glucose levels first appear during pregnancy.
  • Pre-eclampsia - Only occurs during pregnancy and is characterised by high blood pressure (hypertension) and the presence of protein in the urine.
  • Growth & development abnormalities of your baby
  • More prone to infections in the urogenital region.
(Bhattacharya, Campbell, Liston, & Bhattacharya, 2007; Nohr, et al., 2007; Shaw, Nelson, & Moore, 2002)

Obese women are also at risk for;

  • Sleep apnoea - Is a sleep disorder that causes you to temporarily stop breathing while sleeping.
  • Failure to progress in labour
  • Shoulder dystocia (shoulders get stuck during birth)
  • Difficulties monitoring the baby’s heart
  • Difficulties providing pain relief satisfactorily
  • Increased risks for the need for an emergency cesarean section
  • Increased risk of wound infection
  • Increased risk of blood clots
  • Postnatal depression

If you are planning to get pregnant you should consult your GP for advice and assistance on how to lose weight safely before becoming pregnant.

If you ARE pregnant and overweight or obese you should NOT try to loose weight

What is important is that you receive the proper care and support for your specific needs during your pregnancy. Try not to become overwhelmed but rather understand that being aware of the risks is important so that poor outcomes can be limited, both for you and your baby.

Many hospitals provide overweight and obese woman, with special care and extra monitoring through various support programs for women. Ask your GP or hospital to find out if you can access these resources or if there is any relevant information for your needs.

You’ll also find that hospitals can offer you support with your body image, your diet, and exercise programs.

Measuring Obesity

The body mass index (BMI) is a measure used to determine whether you are obese or overweight.

The BMI is limited by a number of factors, such as it does not take into account lean muscle mass, which weighs more than fat, it does not account for variations in fat distribution, age, sex, or culture, which also influence the way we like to look. However it provides an easy means of measurement and calculation which is a good guide for determining who is at risk of obesity and is the internationally accepted practical way of assessing obesity.

What is considered normal BMI versus overweight and obese can vary slightly between countries.

Australia BMI Categories

  • Under 18 - you are very underweight and possibly malnourished.
  • Under 20 - you are underweight and could afford to gain a little weight.
  • 20 to 25 - you have a healthy weight range for young and middle-aged adults.
  • 26 to 30 - you are overweight
  • Over 30 - you are obese

United States BMI Categories

  • Underweight = <18.5
  • Normal weight = 18.5–24.9
  • Overweight = 25–29.9
  • 26 to 30 - you are overweight
  • Obesity = BMI of 30 or greater

How to Calculate your BMI

Your BMI is based on your pre-pregnancy weight. BMI is defined as the individual's body weight (before pregnancy) divided by the square of your height in metres squared (m²).

BMI = mass (kg)/(height (m))²

Calculation examples:

1. Jane weighs 70kg and is 172cm tall

BMI = 70kg/(1.72x1.72)

       = 70/2.9584


This means Jane is in the 'Normal' weight range.

2. Kelly weighs 65kg and is 150cm tall

BMI = 65kg/(1.50x1.50)

= 65/2.25


This means Kelly is in the 'Overweight' range.

Calculate your BMI online:

To calculate your BMI online visit the following sites and just punch in your numbers to find out your BMI.

Assistance During Pregnancy

If you are overweight or obese you will likely receive extra monitoring during your pregnancy, such as;

  • Assessed to see if you have pre-existing diabetes
  • Assessed at 26 weeks for gestational diabetes.
  • Overweight = 25–29.9
  • Your baby will be closely monitored throughout your pregnancy
  • You may be offered more frequent antenatal visits

Technical Reference List

Bhattacharya, S., Campbell, D. M., Liston, W. A., & Bhattacharya, S. (2007). Effect of Body Mass Index on pregnancy outcomes in nulliparous women delivering singleton babies. BMC Public Health, 7(147), 168. Nohr, E. A., Bech, B. H., Vaeth, M., Rasmussen, K. M., Henriksen, T. B., & Olsen, J. (2007). Obesity, gestational weight gain and preterm birth: a study within the Danish National Birth Cohort. Paediatric and Perinatal Epidemiology, 21(1), 5-14. Shaw, G. M., Nelson, V., & Moore, C. A. (2002). Prepregnancy body mass index and risk of multiple congenital anomalies. Am J Med Genet, 107(3), 253-255.



AlbertEinstein_iconOne of the greatest minds in history, Albert Einstein was born preterm.

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Preemie, Premmie, or Prem?

Most babies spend between 38 and 42 weeks in their mother’s uterus. So, technically a preterm birth, preemie, premmie, or prem, is an infant who is born less than 37 completed gestational weeks. 

Read More: Defining Preterm birth



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