Raised BMI in pregnancy

Diabetes that is first diagnosed in pregnancy is known as gestational diabetes. If your BMI is 30 or above, you are three times more likely to develop gestational diabetes compared with women with a BMI under 25. You will be offered a test for gestational diabetes between 26 and 34 weeks.

This may be a simple blood test in early pregnancy and/or a glucose tolerance test (GTT) when you are between 24 and 28 weeks pregnant.

A GTT involves fasting overnight (not eating or drinking anything apart from water) and staying in the hospital antenatal area for 2-3 hours:

• In the morning, before breakfast, you will have a blood test. You are then given a glucose drink.
• The blood test is repeated 2 hours later to see how your body reacts to the glucose drink.

If you have had gestational diabetes in a previous pregnancy, you will be offered either a kit to check your own blood glucose levels or a GTT in early pregnancy. If these are normal, you will be offered a GTT again at 24–28 weeks.

During your routine pregnancy care, your urine is tested for glucose at most appointments. If glucose is present in your urine, then your healthcare team may recommend that you have a GTT.

If the test shows that you have gestational diabetes, you will be referred to a specialist for further testing and treatment as required.

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Women who have a high BMI are at a higher risk of developing high blood pressure. If you develop high blood pressure in pregnancy, you may also develop a more serious condition called pre-eclampsia,which can affect the health of you and your baby. Your midwife will be assessing your health including your blood pressure at each antenatal visit.

Pregnant women are ten times more likely to develop blood clots (venous thrombosis) than women who are the same age and not pregnant. You are even more likely to develop blood clots if your BMI is above 30 at your booking appointment. You are therefore encouraged to stay well hydrated and active during pregnancy and will be advised to wear support stockings, if you are admitted to hospital.

Your midwife will assess your individual risk of developing blood clots. Women who are most at risk of developing blood clots may be prescribed additional preventative medication.

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All women are offered two scans in their pregnancy. These scans check your baby’s major organs and physical characteristics. If you have a high BMI, especially with body fat around your abdomen (tummy), the ultrasound image will not be as clear. This limits your sonographer’s ability to assess your baby’s growth and development.

It is also more difficult to estimate growth or determine your baby’s position during abdominal palpation. Further scans to assess your baby’s growth or position may be necessary in your pregnancy. Your midwife will discuss this with you.

Studies suggest that having a high BMI is associated with an increased risk of stillbirth. If your BMI is above 35 your risk of stillbirth is twice as high as the general pregnant population (8.6 per 1000 births compared to 3.9 per 1000 births). The risk of stillbirth increases with an increasing BMI and the reason for this is largely unknown. It is important to become familiar with your baby’s daily pattern of movements and contact the Maternity Unit if you have any concerns or your baby’s movements are reduced. Please click here for further information

While many women with a high BMI have straightforward births, the likelihood of complications is increased. These complications include:

• induction of labour
• a longer labour
• a caesarean section
• difficulties in hearing the baby’s heartbeat
• larger babies and difficulties delivering the baby’s shoulders
• heavy bleeding after the baby is born
• problems having epidurals and drips inserted
• less chance of having a successful vaginal birth after a previous caesarean section

While you are pregnant you will have a discussion with your healthcare professional about where you will choose to give birth. Depending on your individual circumstances, you may choose to give birth in a consultant-led unit with easy access to medical support if required. For further information on birth place choices please click here

All types of pain relief are available to you. However, having an epidural maybe more difficult if you have a raised BMI. You may be offered a discussion with an anaesthetist to talk about your choices for pain relief during labour.

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To reduce your risk of postpartum haemorrhage (heavy bleeding after childbirth), your healthcare professional may recommend having an injection to help with the delivery of the placenta (afterbirth).

For further information, see the RCOG patient information Heavy bleeding after birth (postpartum haemorrhage)

Breastfeeding has many health benefits for you and your baby. It is possible to breastfeed whatever your weight. Extra help is available if you need it from your healthcare professional and local breastfeeding support organisations.

Find out as much as you can about breastfeeding before you have your baby. You will feel more confident when you start breastfeeding your baby if you have prepared beforehand. 

For further information on the benefits of breastfeeding click here

Please click here for further information on feeding your baby