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Why is it important to be a healthy weight during pregnancy?

Why is it important to be a healthy weight during pregnancy?

Keeping an eye on your weight is always recommended - but it’s even more important to maintain a healthy body weight during pregnancy.

Being overweight during pregnancy can lead to problems not just for the mother, but for the baby too.

In addition to this, it’s essential that you have a healthy Body Mass Index, or BMI. But what are the risks from being an unhealthy weight during pregnancy and having a high BMI - and how can the risks be reduced? This blog post explains.

Your weight, and your BMI, will be recorded by your community midwife at your first antenatal appointment. It will then be checked at 34 weeks. If you have any existing conditions you may be weighed slightly more frequently.

At these appointments you will have your BMI recorded. We recommend, however, that you keep an eye on your weight and BMI yourself, ideally with an easy to use weighing scale at home for convenience. Of course, it will be even easier for you if you’re using BMI scales.

What if your BMI is too high?

A healthy BMI is typically one that is between 18.5 and 25. If your BMI is between 25 and 29.9 it’s regarded as overweight, and if it is above 30 it regarded as obese. It’s worth bearing in mind that nearly 1 in 5 women have a BMI over 30 at the beginning of pregnancy. So if you know your pre-pregnancy BMI - even better!

If you do have a BMI higher than 30 when you have your first antenatal appointment, your midwife will give you information about the risks of high BMI in pregnancy.

If your BMI is over 35 you will be referred to a consultant.

Mother: Risks associated with being overweight during pregnancy
Gestational diabetes

If you have a raised BMI you’re three times more likely to develop gestational diabetes (when diabetes is first diagnosed in pregnancy). If you have a raised BMI you will be offered an Oral Glucose Tolerance Test at 28 weeks to screen for diabetes.


Blood clots can form in your legs or lungs as a result of a raised BMI and being overweight. You’ll already be at a higher risk of thrombosis compared to non-pregnant women, but if your BMI is higher than 30 the risk is increased further.

High blood pressure and pre-eclampsia

Blood pressure will be monitored at your antenatal appointments. You may be referred to an expert if your blood pressure is too high. Women with a BMI of more than 35 at the beginning of their pregnancy are twice as likely to develop pre-eclampsia as women with a lower BMI.

Baby: Risks associated with being overweight during pregnancy

If your BMI is more than 30 in the first 12 weeks of pregnancy the risk of miscarriage increases from 1 in 5 to 1 in 4.


The mother’s raised BMI can cause the baby develop diabetes, and even suffer with obesity later on in life.

Large baby

Having a BMI over 30 doubles the chances of your baby weighing over 4kg.


Additionally, having a BMI of 30 doubles the risk of stillbirth (i.e from 1 in 200 to 1 in 100).

Labour issues

Being overweight can also affect labour. Your baby is more likely to be born premature, labour time could increase and there is also increased risk of Shoulder Dystocia (where the baby’s shoulders get stuck during birth).

How can the risks be reduced?
Eat healthily

Gaining weight is a part of pregnancy. However, the amount of weight women gain through pregnancy varies greatly.

It’s worth remembering that a healthy diet will not just benefit you, but your baby too. It is not recommended that you actually lose weight during pregnancy, however you should try to keep weight gain under control as much as possible. Base your meals around starchy foods such as pasta, bread and rice, avoid the trap of ‘eating for two’ (it’s not necessary), and go for foods with low fat content.

Eating five or more portions of fruit and vegetables a day and eating fibre-rich foods (like oats, beans, brown rice and seeds) will also help. More detailed help and advice regarding healthy eating during pregnancy is provided by the NHS.

Get regular exercise

You’ll find it harder and harder to move about the further you get into pregnancy - but start early on with a routine of regular exercise and you could avoid being overweight and suffering the associated risks.

Simple exercises like walking up and down stairs, going for a walk and cycling are all low-impact solutions for regular exercise. Build swimming and walking into daily routines too. The NHS recommends that you start with 15 minutes of continuous exercise, three times per week, gradually increasing to 30 minutes every day.

Take supplements

Taking folic acid tablets will help to reduce the risks of your baby having a neural tube defect (when the skull or spine does not form properly).

If your BMI is higher than 30 you will need to take slightly more folic acid - 5mg a day is recommended. Folic acid will need to be prescribed by a doctor, and should ideally be taken before conception until 13 weeks of pregnancy.

All women, regardless of BMI and weight, are advised to take Vitamin D supplements every day - 10 micrograms per day is the recommended dosage. Women with a high BMI are at a higher risk of Vitamin D deficiency.

Weigh yourself

Keeping track of your weight regularly will help you track your progress through pregnancy. Ideally, the weighing scales you use will have a BMI calculation feature and be of comparable accuracy to those used by your midwife.

BMI scales are now widely available and almost all Marsden medical scales have BMI calculation. This makes them great for regularly checking your weight during pregnancy. The Marsden M-545 is a portable option with BMI calculation and, with a graduations to 100g, it’s as accurate as almost any weighing scale you’re likely to be weighed on by a midwife, health visitor or nurse.

The Marsden M-550 is a lightweight floor scale with BMI calculation. It has a tap-on feature too - perfect for when you get into the latter stages of pregnancy, since you don’t need to bend down to switch it on!

Finally, for weighing your newborn, we recommend the highly accurate, easy to use Marsden M-300 from our Baby Scales range.

To find out more about weighing scales suitable for home use call the Marsden team on 01709 364296 or contact us here.