Expert / 27 November, 2020 / Dr. Nauf AlBendar

Everything You Need To Know About Your Baby’s Birth Weight

The importance of birth weight

Birth weight is the first weight of a baby, taken just after he or she is born, and is one of the most utilised parameters in assessing the health and wellbeing of a newborn.

The average birth weight in babies of European heritage is 3.5 kilograms and of South Asian and Chinese heritage 3.26 kilograms.

Birth weight can be affected by many environmental factors as well as some genetic factors during pregnancy as well as foetal growth. But it has shown to be a relevant indicator of the womb environment and can be used to predict a child’s vulnerability in relation to subsequent health, development and disease.

In the early 1990s, the “programming hypothesis” was suggested to describe the observed associations between birth weight and adult health. Since then, the importance of pregnancy and early life in relation to later disease has been widely acknowledged and studied.

Birth weight is considered a public health priority for its short and long-term implications on health and survival.

Low birth weight

Low birth weight is when a baby is born weighing less than 2,500 grams (2.5 kilos). Some babies with low birthweight are healthy, even though they are small. But being low birth weight can cause for the majority of newborns serious complications, and is a substantial public health concern in every country. 15% to 20% of all births worldwide are low birth weight.

There is a considerable variation in the prevalence of low birth weight across regions and within countries; however, the great majority of low birth weight births occur in low- and middle-income countries and especially in the most vulnerable populations.

South Asia has the highest low birth weight births to date, accounting for nearly half of all low birthweight newborns in the world. The developed countries of North America, Europe, Japan, Australia and New Zealand, account for approximately 7% of the world’s low birth weight births.


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What are the causes of low birth weight?

There are two main reasons why a baby may be born with low birthweight, the duration of pregnancy and the rate of foetal growth.

1.Premature Birth (before 37 weeks of gestation). This is when a baby is born earlier than 37 weeks of pregnancy. Being born too early means a baby has less time to grow, develop and gain weight in the womb.


2. Foetal growth restriction (also called small for gestational age, SGA). This means a baby doesn’t gain the weight he or she should before birth. Some growth-restricted babies may have low birthweight simply because their parents are small.

Others may have low birthweight because something slowed or stopped their growth in the womb.

Globally, 60–80% of neonatal deaths occur among low birth weight infants, of which two-thirds are preterm and one third are term small-for-gestational-age. The majority of low birth weight babies would need different clinical and nutritional interventions and special care in the NICU until they gain weight and are well enough to go home.

Paediatricians have long been familiar with the increased risk of mortality and early morbidity of babies born very small or very early. These babies have a greater risk of dying throughout the first year of life. In addition, they are more likely to have a range of morbidities, particularly neurological, respiratory, and gastrointestinal.

Low birth weight babies are also at higher risk of developing complications, behaviour and psychological problems during their life span and can be surrogates of insulin resistance which is a key factor leading to type 2 diabetes, cardiovascular disease as well as kidney diseases and kidney failure in adulthood.

The various determinants of having a low birth weight baby:

Having proper knowledge of the risk factors for low birth weight is important for identification and giving appropriate attention to those mothers at risk. Below are some of the most common risk factors:

?      Women of certain ethnicities and from deprived socio-economic conditions frequently have low birth weight babies.

?      Low birth weight can also vary by maternal age. Being a teen mother (especially younger than 15) or being older than 40 can increase the susceptibly of low birthweight.

?      The health of the mother before and during pregnancy. A pre-existing condition is sometimes associated with decreased birth weight. For example, hypertensive disorders of pregnancy

?      Certain medications (e.g. for high blood pressure or epilepsy) can put a mother at a higher risk for delivering a low birth weight baby.

?      Infections (e.g. malaria)

?      Problems with the placenta. Complications in the placenta can reduce the flow of oxygen and nutrients to you the growing baby, limiting its growth.

?      Not gaining enough weight during pregnancy. Women who don’t gain enough weight during pregnancy are more likely to have a low-birthweight baby. It is important for women with eating disorders or that have been treated for an eating disorder to inform their GP.

?      Having a premature or a growth-restricted baby in the past

?      Multiple births, where a mother has more than one child at one time. Multiple births put children at a higher rate to have low birth weight (56.6%) compared to children born in a single birth (6.2%).

?      Environmental factors, including exposure of the mother to second-hand smoke, nutritional status, air pollution, and tobacco and drug use can slow a baby’s growth in the womb and increase the risk for premature birth and birth defects.

?      Stressful events have been demonstrated to produce significant effects on birth weight. Mothers who have had stressful events during pregnancy and even prior to conception, are at higher risk to deliver low-birth-weight babies.

?      Women who experienced abuse (physical, sexual, or emotional) during pregnancy are also at increased risk of delivering a low-birth-weight baby

High Birth Weight

A big baby, according to common knowledge, is a healthy baby. But bigger is not always better when it comes to a baby’s birth weight.

Although most of the focus in birth weight research relates to low birth weight, high birth weight is now becoming a topic of interest because of its long term risks.

High birth weight is when a baby tends to be larger than 4,500 grams (4.5 kilos) and is often born after term. This is also known as ‘foetal macrosomia’ or large for gestational age (LGA).

A baby may have a high birth weight due to genetic factors, the mother’s health or, in rare cases, a medical condition that causes the foetus to grow too quickly.

Parents that are overweight or mothers with diabetes during pregnancy -otherwise known as gestational diabetes- can also influence this excessive growth. The latter being the most common factor, larger babies would need to be monitored closely after birth to help regulate their blood sugar levels. They are also at increased risk for jaundice and childhood obesity.

High birth weight can also increase the risk of adverse outcomes of delivery, birth injuries and complications. Adults with high birth weight tend to have a higher risk of obesity, type 2 diabetes as well as adult-onset cancers such as prostate cancer and possibly breast cancer.

What can you do to ensure you have a baby with a healthy birth weight?

It is important to remember that not all high birth weight or low birth weight babies will have adverse outcomes. And that the trend for successive babies is to get bigger, so this is something to be taken into consideration.

To grow a healthy baby, mothers need good nutrition and rest, adequate antenatal care and a clean environment. These ingredients for a healthy pregnancy can help prevent, identify and treat the conditions that cause low or high birth weight and keep babies alive and thriving.

It is equally important to focus on the health of women prior to conception through reproductive education, screening and counselling regarding mental health issues and stress, and access to primary care.

By taking into consideration the birth weight of a baby, it could help parents be proactive and tackle the risks early with their GP and reversing the lifelong consequences with adequate diet and lifestyle habits earlier on.

Below are some tips to grow a healthy baby with a healthy birth weight:

Good diet and nutrition

Eating a nourishing, well-balanced diet during pregnancy is important for your baby’s development. A good diet can contribute to healthy birth weight and can reduce the risk of many birth defects. Remember that your antenatal diet should include proteins, omega-3’s, vitamin C, calcium, magnesium, fruits and vegetables, fermented foods, whole grains, iron-rich foods, good fats, and choline. Try and supplement with antenatal supplements, folate/ folic acid, vitamin D and probiotics where you can.

Take care of yourself

Take time to look after yourself throughout your pregnancy journey and try to foster a safe, calm and positive environment. Allow yourself to rest, surround yourself with adequate antenatal care, and avoid indoor and outdoor pollution as much as possible, as this can have a significant impact on birth weight.

Lowering stress

Pregnancy can be an emotionally overwhelming time, but please remember that you’re not alone. Try and prioritise putting strategies in place to manage your stress as high-stress levels during pregnancy may cause health problems and increase the chances of having a premature or low-birth-weight baby. Think about how you like to relax, whether that involves yoga, guided meditation or picking up a good book, try and implement these things into your daily routine.


It can be difficult to fit exercise into your busy day, but try and make time for a morning walk or family bike ride. Moderate exercise for 30 minutes or more each day can not only beneficial to you and your baby but also prevent gestational diabetes, a condition that poses risks to the developing baby and can affect birth weight. Now’s the time to get your exercise in, but do make sure to listen to your body.

Maintaining a healthy weight

When trying to conceive, it’s ideal for both parents to maintain a healthy weight. During pregnancy, keep an eye on your weight and be mindful of what an appropriate weight gain should look like for you. This will be in accordance with the pre-pregnancy weight, body mass index (BMI), personal factors (such as previous or current eating disorders) or whether you’re carrying twins or multiple.

These tips for a healthy pregnancy can help prevent, identify, and treat the conditions that cause low or high birth weight and ensure your baby thrives. It is also important to focus on your health as a parent by surrounding yourself with helpful resources such as reproductive education, access to primary care, screening, and counselling regarding mental health issues and stress which all can affect birth weight.

To support the healthy development and birth weight of your baby, please be proactive and tackle the risks early with your GP and help reverse the lifelong consequences with an adequate diet and lifestyle.

Article by Dr Nauf AlBendar, medical scientist and expert in foetal origins of disease. Founder of The Womb Effect, an educational platform for aspiring and expecting parents.


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