Raised BMI (Body Mass Index) in pregnancy – what you need to know

Your health and diet has a direct effect on not only your wellbeing, but your baby’s too.

This includes your Body Mass Index – or BMI – which is why this is measured by your midwife at the start of your pregnancy and again at 36 weeks.

Body Mass Index

Your BMI is calculated using your body weight and height.

• A healthy BMI is between 18.6 and 24.9
• If your BMI is lower than 18.5 you will be classed as being underweight
• between 25.0 and 29.9 is overweight
• anything above 30 is obese.

There are three classes of obesity:

• Class 1 is a BMI of 30 to 34.9
• Class 2 is a BMI of 35 to 39.9
• Class 3 is a BMI of 40 or more

If your BMI is more than 30, you will be given information by your midwife about how this can affect your pregnancy, childbirth, and the post-natal period.

The recommended weight gain in pregnancy for those whose BMI is more than 30 is between 5-9kg (11-20 pounds)

What are the risks?

Gestational diabetes

There is an increased chance of developing a condition called Gestational Diabetes Mellitus during pregnancy.

What can be done?

You will be offered a glucose tolerance test at 24 to 28 weeks and will be referred to a clinician if this shows you have developed the condition, so that you can discuss and put in place a plan for your ongoing care.

Blood clots

There may be an increased chance of developing blood clots in your legs or lungs. Assessments will be made throughout your pregnancy and a plan of care will be discussed with you if you have an increased chance of this happening to you.

What can be done?

You’ll be assessed at your booking appointment and again later in your pregnancy. If anything changes in your health during your pregnancy, this assessment may need to be performed again.

Your midwife and/ or doctor will discuss treatment options with you. This may include injections to thin your blood, which helps to prevent clots from forming.

High blood pressure

Raised blood pressure and protein in your urine are a sign of pre-eclampsia.

What can be done?

You might be offered a low dose of aspirin, which is safe to take and has proven to be effective in preventing high blood pressure. This will be discussed with you at your booking appointment and when you attend the hospital for your initial dating scan.

Problems with accuracy in scanning

• Occasionally there are difficulties obtaining accurate information when performing a dating scan and obtaining a nuchal fold measurement. This can affect the precision of Downs syndrome screening. If this happens, then you will be offered one further attempt to obtain the measurement. Your midwife and/or doctor will discuss the options with you if this measurement still cannot be obtained.
• There may be other scans where it is difficult to get accurate measurements. Your doctor will discuss this with you and together, you can make a plan of care

Anaesthetic appointment

It’s extremely important you attend this appointment if you’re offered one, as it will help both you and your doctor be prepared, should anaesthesia be neccessary.

It will also help the team decide if any moving and handling equipment may be needed and you will be able to discuss the details of anaesthesia used in labour and raise any concerns or points you wish to discuss.

What happens in labour?

• Your Community Midwife will talk to you about your birthing options. You may also need to discuss this with your doctor and, if this is the case, the midwife can arrange this appointment for you.
• We will give you an antacid tablet (such as Omeprazole) during your labour, which reduces acidity in your stomach
• We advise that you keep yourself hydrated with isotonic drinks
• Monitoring you and your baby may be more difficult if you have a high BMI. It may be that we will need to use a clip, which is attached just under the skin of your baby’s scalp. If we believe this is required, we will discuss this with you and obtain your consent.

Risks in labour and at birth

• There’s an increased chance of pre-term labour – particularly if your BMI is greater than 40
• There is also an increased chance of you needing to be induced (using medication to start your labour)
• Longer labour
• Challenges in monitoring baby’s heartbeat during labour
• Baby’s shoulders may become stuck when they are being born (shoulder dystocia)
• There’s an increased chance of needing interventions in labour, such as requiring forceps or ventouse assistance
• Increased chance of emergency Caesarean
• Increased chance of developing complications such as wound infection and delayed recovery
• Chance of increased and/or excessive risk of having heavy bleeding after childbirth

What can be done?

• Healthy eating
• Exercise
• Monitor your weight gain during pregnancy
• Attend antenatal appointments regularly to monitor your baby’s growth, your blood pressure and have your urine checked

Healthy eating

• Don’t try and lose weight
• Base your meals on whole grain, starchy foods – such as potatoes, bread, and pasta
• Watch your portion size
• Eat more fruit and vegetables
• Fibre-rich foods, such as oats, beans, lentils, grains, seeds, fruit and vegetables should take priority over foods which are higher in fat and sugar
• In general, you don’t need extra calories during the first two thirds of pregnancy. It’s only in the last 12 weeks that you need an additional 200 calories per day
• Losing weight in pregnancy, even if you’re obese, is not recommended
• Take a pregnancy multivitamin throughout your pregnancy

Exercise

• Make activities such as waking, cycling, swimming, and low impact aerobics, part of your everyday life
• Aim to exercise for 15-30 minutes, three times a day but start gradually, perhaps exercising three times a week initially to build up your fitness
• Active lifestyle – incorporate gardening, going up and downstairs, instead of using a lift and regular walking for short distances

Care after Childbirth

• Breastfeeding is best for your baby and for you
• The risk of blood clots persists for six weeks after childbirth and you may be advised to continue with blood thinning injections, depending on your circumstances
• You may be offered testing for diabetes if you experienced problems in pregnancy and to check that you do not develop it afterwards
• You may need blood pressure monitoring after childbirth for six week if you had problems with blood pressure in pregnancy

Weight loss

• Weight loss is recommended between pregnancies. A steady loss of 1-2 pounds per week is recommended
• Improving or decreasing your BMI often increases your chances of conception and/ or helps resolve menstrual problems