Weight management before, during and after pregnancy has a considerable impact on individual health outcomes for women and their baby. As a result, education and advice on healthy weight-management at all stages of conception and pregnancy are vital in the care of pregnant women.

Accredited Practising Dietitian Stefanie Valakas said while gestational weight gain is normal, natural and necessary for a healthy pregnancy to support expanding tissues, blood volume and the growing baby, being under or overweight can have negative health consequences.

“Eating too much or too little during your pregnancy can lead to too much or too little weight gain, which is not ideal for the mother, her baby or the birth.

“Too little weight gain during pregnancy has an increased risk of pre-term birth and a baby small for gestational age, with a potential for lifelong effects on the baby.

“The Dutch Famine in 1944-45, showed that children born to mothers who were pregnant during a period of poor food availability led to increased risk of being obese and numerous chronic diseases later in life such as type 2 diabetes, heart disease and renal dysfunction 40 to 50 years later,” said Ms Valakas.

Fertility and Prenatal Dietician Melanie McGrice said gaining too little weight during pregnancy is problematic, with malnutrition, low birth weight and future weight problems for the baby common risks.

“Contrary to what you may expect, childhood obesity may also be a side effect of not gaining adequate weight during pregnancy, as if a baby gains weight too quickly after being underweight, research suggests that it can impact the baby’s fat storage hormones,” said Ms McGrice.

Similarly, gaining too much weight during pregnancy also increases future overweight and obesity risk for the baby.

“When mothers gain too much weight during pregnancy, it significantly increases the baby’s risk of future weight battles.

Excess weight gain during pregnancy also increases the risk of high blood pressure, gestational diabetes, development of diabetes later in life, difficulty losing weight post-partum, said Ms Valakas.

“Women who gain too much weight during pregnancy are more likely to have a large baby, which increases the risk of delivery interventions, including C-sections. 

“In fact, for women with a BMI over 30, there is a 9-fold risk of gestational diabetes which can lead to a large for gestational age baby and increased birth complications and interventions,” said Ms Valakas.

Women with a BMI over 30 are also twice as likely to undergo a C-section, have a three-fold increased risk of developing pre-eclampsia, and 7 per cent increased risk of neural tube defects such as spina bifida and are also at an increased risk of pre-term birth and NICU admissions.

Alarmingly, research shows that 70% of women do not gain within the recommended gestational weight guidelines during pregnancy, and less than 30 per cent of women knew what was appropriate for them to gain during pregnancy, explained Ms Valakas.

“There is a huge opportunity for midwives and nurses to educate pregnant women on this topic to improve pregnancy and birth outcomes.

“Midwives and maternity nurses can support appropriate weight gain during pregnancy by taking the weight of women at each appointment and plotting it on a pregnancy weight gain chart.

“Research suggests that integrating a prompt into your medical records or check-up checklists is the best way to increase measurements being taken and recorded.

“It may feel like a sensitive or emotional topic to talk about, but pregnant women are interested in knowing how much weight to gain for a healthy pregnancy. Of course, approaching it in a caring and empathetic way is the best course of action.

“If weight gain is too much or too little, note that with the patient and have a discussion about lifestyle habits and flag it with their obstetrician. Then refer to an Accredited Practising Dietitian with expertise in pregnancy nutrition for further management and preventing birth complications and to reduce the future health risks for both mother and baby,” said Ms Valakas.

How much is too much?

Health care professionals should refer to the Institute of Medicine guidelines on gestational weight gain, which reflects appropriate weight gain ranges based on pre-pregnancy body mass index (BMI).

If the patient is pregnant with triplets or multiples, it can be more difficult to accurately determine optimal ranges of weight gain as there is little data available at present, according to Ms Valakas.

“You can then calculate weekly target weight gain per week for pregnant women based on their pre-pregnancy BMI from the second trimester onwards.

“Unless starting with a BMI below 18.5, the goal is for no more than 2 kilograms of weight gain for pregnant women in the first trimester as a pregnant woman's calorie or energy needs are not increased at this time, and therefore weight gain should be minimal,” said Ms Valakas.

Starting the conversation

Although there are guidelines for weight-management, it’s important to remember that they are just guides, explained Ms Valakas.

“They are a perfect starting point to have a conversation with pregnant women about gestational weight gain and their lifestyle.

“Point out its importance for not only a healthy pregnancy but a healthy child and reducing the risk of complications during labour and delivery,” said Ms Valakas.

Optimising weight before conception is ideal, said Ms McGrice, but not all pregnancies are planned, but the good news is, it's not too late.

“If a woman’s overweight at conception, gaining the right amount of weight during pregnancy can still help to reduce risks,” said Ms McGrice.