During a healthy pregnancy, women gain weight as the baby grows. This is normal and necessary.

But recent research indicates that excessive weight gain during pregnancy increases health risks for mothers and their children.

So how do you get the right balance?

Weight gain guidelines

Recommended weight gain in pregnancy is based on body weight and body mass index (BMI) prior to becoming pregnant. If your pre-pregnancy BMI is:

• less than 18.5, aim to gain between 12.5 and 18 kg
• 18.5 to 24.9, aim to gain 11.5 to 16 kg
• 25.0 to 29.9, aim to gain 7 to 11.5 kg
• 30 or more, aim to gain just 5 to 9 kg.

Most weight gain occurs from week 13. For some women, body weight will not change too much during the first trimester of pregnancy, particularly for women who have had morning (noon and night) sickness.

Further reading – Health Check: what can you eat to help ease morning sickness in pregnancy?

Weight gain recommendations are higher for those having twins, with the target range depending on the woman’s pre-pregnancy BMI: 18.5-24.9 (weight gain: 17-25 kg), 25-29.9 (weight gain: 14-23 kg) and 30 or more (weight gain: 11-19 kg).

A recent review covering more than one million pregnancies found half the women gained too much weight. Even women who started pregnancy at a healthy weight (those with a BMI of 18.5 to 24.9) typically gained too much weight.

Our study of women in the United Kingdom found excessive weight gain was more common among women who were having their first baby.

Why is it important?

Gaining too much weight in pregnancy can affect the mother’s health. Excess weight gain has been linked to a higher risk of developing diabetes in pregnancy, high blood pressure, and complications during birth.

It can also affect the health of the baby in both the short-term and in the future. In a review of one million pregnancies, mothers who gained too much weight in pregnancy were more likely to have babies with a high birth weight compared to other mothers. Children of the mothers who gained too much weight were then at a higher risk of becoming obese as a child or adult.

Read more – Health Check: eating for two during pregnancy

Excess pregnancy weight gain can also make it more challenging to lose weight after the baby is born. Our recent study showed that women who gained more weight than recommended retained, on average, an extra 4kg six months after their baby was born. Of concern is that this extra weight can still be retained decades after pregnancy. Not shifting those extra few kilos after pregnancy increases the chances of developing obesity in the future.

Not gaining enough weight in pregnancy can also be a problem. Weight gain below the recommendations is associated with having a baby that is small for gestational age, or a preterm birth.

It’s important for women not to try and lose weight during pregnancy. Dieting or limiting food intake could mean the baby doesn’t get enough nutrients needed for their development.

Five tips for healthy pregnancy weight gain

1. Start a conversation with a doctor or midwife. While talking about weight during antenatal visits can make some pregnant women feel anxious, knowing how much weight is appropriate can help improve the pregnancy outcomes for women and their infants. Having this conversation is important because a doctor or midwife can provide support. They can also refer pregnant women to a dietitian or other service, if needed.

2. Track weight gain from early in pregnancy. Monitoring weight in pregnancy can help keep weight gain “on track”. Try a pregnancy weight tracker; such as this one for women with a pre-pregnancy BMI of less than 25, or this one for women with a pre-pregnancy BMI of more than 25. Start recording weight as early in pregnancy as possible.

Remember every pregnancy is different, and the amount of weight gained each week won’t be identical. But it’s a great way to “keep check” and see whether weight gain patterns are tracking above or below the recommendations.

3. Focus on healthy eating. It’s a myth that you need to “eat for two” during pregnancy. During the first trimester, dietary energy needs (measured in calories or kilojoules) are only slightly higher so the amount of food eaten should remain about the same. But nutrient requirements increase, particularly for folate, iodine and iron, so women need to be mindful of the nutritional quality of food eaten.

While more food energy is needed during the second and third trimester, the amount of extra food is less than most people think. It would be the equivalent of a sandwich (such as egg, beef, hummus or cheese), or a yoghurt and banana. Use the Eat-for-Health Calculator to calculate the recommended daily serves from the five food groups to give you an idea of what you should be eating during pregnancy.

Read more – Health Check: what to eat and avoid during pregnancy

4. Exercise regularly. Being active is important during pregnancy. The national recommendations advise the accumulation of 150 minutes of exercise each week. Many exercises are safe during pregnancy, such as walking, swimming, stationary cycling and pregnancy-specific exercise classes. Doctors, midwives, exercise physiologists and physiotherapists can provide advice about the best options.

5. Enlist the support of a partner and family. Having a healthy lifestyle that includes eating healthily and being active is not just important for the mother and baby in pregnancy, but can also benefit other family members.

Clare Collins is affiliated with the Priority Research Centre for Physical Activity and Nutrition, the University of Newcastle, NSW. She is an NHMRC Senior Research and Gladys M Brawn Research Fellow. She has received research grants from NHMRC, ARC, Hunter Medical Research Institute, Meat and Livestock Australia, Diabetes Australia, Heart Foundation, Bill and Melinda Gates Foundation, NIB Foundation. She has consulted to SHINE Australia, Novo Nordisk, Quality Bakers and the Sax Institute. She was a team member conducting systematic reviews to inform the Australian Dietary Guidelines update and 2017 evidence review on dietary patterns for the Heart Foundation.

Dr Jenna Hollis has received an Endeavour Postdoctoral Research Fellowship from the Department of Education and Training (Australian Government). She has also received funding from the Hunter Medical Research Institute (HMRI), the University of Newcastle (Australia), and the Australian and New Zealand Obesity Society (ANZOS). Jenna is a Project Officer at Hunter New England Population Health (NSW Health), a Conjoint Lecturer at the University of Newcastle, and a Visiting Research Fellow at the Medical Research Council Lifecourse Epidemiology Unit, University of Southampton (UK). She is affiliated with the Priority Research Centre for Physical Activity and Nutrition and the Priority Research Centre for Health Behaviour, at the University of Newcastle. She participated in the Australian Academy of Science and Theo Murphy’s High Flyers Think Tank on Food and Nutrition Science in 2017, and the European Nutrition Leadership Platform in 2015.

Siân Robinson is supported by the UK Medical Research Council and by the National Institute for Health Research through the NIHR Southampton Biomedical Research Centre.