Pregnancy weight gain: is there a right amount and why does it matter?

Pregnancy weight gain is normal and healthy. While you’re pregnant you’ll progressively gain weight to support your baby’s growth and development and to prepare your body for breastfeeding. However, a recent global study has found that nearly 75% of women don’t gain a healthy amount of weight during pregnancy, with 23% not gaining enough weight and 50% gaining too much. So what is the right amount of weight to gain and why does it matter?

How much weight should you gain?

While every woman will gain weight differently during pregnancy, your total weight gain for the entire pregnancy should sit somewhere between 11.5–16 kgs. All women can expect to gain 1–2 kg during their first trimester (up to 3 months). From there, your ‘healthy’ rate of weight gain depends on how much you weighed before you became pregnant. If you were carrying some extra weight before pregnancy, you are advised to gain less weight than someone starting off in a lower weight range:

Pregnancy weight gain chart

Pre-pregnancy weight	Total weight gain recommended	Recommended weight gain per week in second and third trimesters (3–9 months)
Underweight (BMI <18.5)	12.5–18 kg	500 grams
Normal weight (BMI 18.5–24.9)	11.5–16 kg	400 grams
Overweight (BMI 25–29.9)	7–11.5 kg	Less than 300 grams per week
Obese (BMI ≥30)	5–9 kg	Less than 300 grams per week

Source: US Institute of Health

If you are carrying twins or triplets, you will need to gain more weight in order to provide enough nutrients for all of your babies. In this case, your total weight gain for the pregnancy should sit higher at around 11–24 kg (depending on your BMI before becoming pregnant).

Why is gaining too much weight a problem?

Excess weight gain during pregnancy can increase your risk of medical complications. The most serious of these is pre-eclampsia, a condition where the blood flow to the placenta is restricted, meaning your baby may not get the oxygen and nutrients it requires. Pre-eclampsia is characterised by high blood pressure, severe fluid retention and protein in the urine, all of which are signs we monitor for during your routine antenatal visits. Gaining too much weight also puts you at increased risk of gestational diabetes, a type of diabetes that occurs during pregnancy due to hormonal changes that make it harder for your body to keep blood sugar levels in check. Unfortunately, if you are overweight when entering pregnancy, your risk of these particular complications is even higher (you can read more about that here).

In the longer term, the extra weight you put on during pregnancy (over and above what you and your baby really need) does tend to be harder to lose. And this sustained increase in weight can elevate your risk of suffering from a range of health conditions such as type 2 diabetes and high blood pressure – making it hard for you to keep up with your growing/busy child.

Gaining too much weight during pregnancy can also impact the health of your baby. If you are overweight while pregnant, your baby is more likely to be born overweight, to be large for gestational age (i.e. be larger than expected given the stage of your pregnancy) and to require a caesarean delivery. Because excessive weight gain can adversely affect placental function, having a baby that is too small (growth restriction) is more likely too. Your child is also more likely to suffer from childhood obesity and to develop metabolic syndrome (heart disease, stroke and diabetes) in later life.

Why is gaining too little weight a problem?

While it’s important for your own health and the health of your baby to keep weight gain in check during pregnancy, it’s also important that you do not try to lose weight during your pregnancy. If you diet, skip meals or restrict your intake of certain food groups, your baby may not get the nutrients it needs for its development. This can lead to premature birth and/or increase the likelihood that your baby will be underweight and small for gestational age.

How can I safely manage my weight during pregnancy?

Not ‘eating for two’ and making sure that what you are eating is, for the most part, healthy and nutritious, is one of the best ways to achieve a healthy pregnancy weight. I recommend women follow a low sugar and carbohydrate diet such as this one from the CSIRO. Many established guidelines on healthy eating during pregnancy are old fashioned, and may promote weight gain by encouraging intake of fruits (high in sugar) and carbohydrate-rich foods containing refined flours such as pasta and bread, which should really be avoided. For SAFE EATING practices during pregnancy, see this handy guide.

It’s also important to remain active during pregnancy – exercising is both safe and healthy, and has benefits for you and your baby. The recommended level of activity changes during the course of your pregnancy (see this helpful guide) and also depends on how much exercise you were doing before you became pregnant. In general, you should do at least 30 minutes of moderate-intensity physical activity on most days of the week. You can find more information on the benefits of exercise during pregnancy and suggested exercises here. Of course, you should always check with your doctor before embarking on any new exercise routine.

Need help establishing a healthy pregnancy lifestyle?

If you would like more information or feel like you are struggling with pregnancy weight gain, diet or physical activity, don’t hesitate to raise these topics with me during your next antenatal appointment. For advice in-between appointments, call my rooms on (03) 9418 8299.