Low Birth Weight in Babies – Causes, Facts, Factors And More

9 min read

Written by Editorial Team

Editorial Team

Low Birth Weight in Babies


Babies born with low birth weight are often a source of concern and worry for parents. There are many reasons for low birth weight in babies, ranging from genetics to the mother’s medical issues. Very low birth weight babies have the highest risk of survival and thriving while the risk reduces with higher birth weight babies. At the same time, not all premature births are associated with risk to life.

A low birth baby’s ability to cope up and thrive will depend on various factors including the reasons for prematurity, the post-birth medical care and the care and precautions that parents take. Here are a few more factors about low birth weight babies and how parents can cope up and help their babies develop through the risk period.

In This Article

What is Considered as Low Birth Weight in Babies?

A baby whose birth weight is less than 2.5 kilograms is considered to have low birth weight. About 6% of all babies are estimated to be born with a low birth weight. However, it is important to understand that not all low birthweight babies have some underlying medical condition or problem. Sometimes, babies are just born small for no particular reason.

How Does Low Birth Weight Affect My Baby?

How Does Low Birth Weight Affect My Baby

In many cases, a low birth weight will not impact your baby’s growth and development. This is especially true if the baby was born full-term with no other underlying medical problems. However, when the baby is born premature, or if the baby is born full-term but with some underlying medical problems, then a low birthweight baby can increase the following risks in your baby

  • Infections
  • Polycythemia (blood thickening)
  • Respiratory Distress Syndrome (RDS)
  • Hypoglycemia
  • Problems with the immune system
  • Problems in lung function
  • Breathing problems
  • Body temperature issues- the baby might not be keeping warm enough
  • Slower rate of development

How severe these problems depend on how low the birth weight is. It also depends on the cause of the low birth weight and the stage of pregnancy when growth restriction started.
Some people correlate low birth weight to lower intelligence and poor health, but there is no strong evidence to prove these myths.

3 Important Facts About Ideal Weight in Infants

As a parent, you would always want to know and understand the important facts about your baby’s ideal weight at birth and how it should increase as they grow. Here are some tidbits for you.

  1. During the first three to four days, the baby loses around 7% to 10% of their body weight. However, this 10 per cent loss will be gained by the baby during the second week after birth. After breastfeeding for six months, the baby gains at least two pounds of weight every month.
  2. The weight of newborn babies increases by two times once they reach their 4th month. After twelve months, that is, after or around the first birthday, you can expect their weight to triple their birth weight.
  3. During the first 2 years, the growth of the baby will be quite rapid, and this will lead to fluctuations in the ideal weight for infants. After 24 months, the growth stabilizes and the baby will start to put on weight in a steady manner.

Top 12 Causes of Low Birth Weight in Babies

Causes of Low Birth Weight in Babies


The cause of the low birth weight in your child is more important than the actual weight itself. This is because the cause determines your baby’s health as he grows up. The following are the top 12 causes of low birth weight in children:

1. Preterm birth

If your baby is born before 37 weeks of gestation, then they will most likely be underweight.

2. Multiple Pregnancies

If you are carrying multiple gestations, i.e. if you are having twins, triplets or more, you have higher chances of giving birth to babies who are less than the ideal 2.5 kgs. This is because more number of babies are competing for the space inside the uterus and nutrition as well.

3. Intrauterine Growth Restriction (IUGR)

These babies are born full-term but still are “small-for-gestational” age. They are most likely healthy, especially if the lower birth weight is due to genetics. There are two kinds of IUGR.

a. Asymmetrical IUGR

This happens due to malnutrition or high BP in mothers. The baby has disproportionately low fetal parameters and the body size may be lesser compared to the head size.

b. Symmetrical IUGR

This type of IUGR happens due to intrauterine infections, abnormalities in chromosomes and mother’s lifestyle (e.g. alcohol abuse). In this condition, the baby develops slowly throughout the pregnancy and is always below the ideal weight range. These babies are more likely to have health problems throughout their lives

4. High Blood Pressure in Mother

If the mother has high BP, then the blood flow to the baby from the placenta is impacted, resulting in low birth weight

5. Substance Abuse by The mother

If the mother smokes or uses illegal drugs or alcohol, it can restrict the baby’s growth and hence impact the weight. The drugs pass to the baby through the placenta resulting in health issues including low birthweight in the baby born.

6. Placenta-related Problems

If the mother is affected by any of the placenta-related problems (e.g. pre-eclampsia or placenta previa), then the flow of blood and nutrients to the baby is impacted, resulting in lower weight.

7. Diabetes

While diabetes is known for resulting in a big baby, it can also result in preterm birth which will impact baby’s weight.

8. Uterus Abnormalities

Sometimes the baby cannot grow big due to the restrictions imposed by the uterus, such as fibroids and uterine malfunctions.

9. Cervix Abnormalities

If the mother has cervix abnormalities, it can also result in low birth weight. An incompetent cervix may spur a premature delivery and birth as it gets pressurized to open as the baby grows. Cerclage, a stitch on the cervix is generally put and the mother is advised complete bed rest in many cases.

10. Mother’s Nutrition During Pregnancy

If the mother has not gained enough weight during pregnancy due to malnutrition or an imbalanced diet, it can affect the baby’s weight. A baby needs a constant supply of nutrients to grow and develop, and the mother’s diet is the primary source of nutrition for her. Not eating a balanced and healthy diet can increase the chances of having a low birthweight baby

11. Infections During Pregnancy

Infections and the drugs used to fight infections during pregnancy can impact a baby’s weight gain.

Read more on infections during pregnancy here

12. Previous Birthing History

Prior preterm deliveries or low birth deliveries will increase the probability of a low birth delivery subsequently

Top 12 Factors That Affect Ideal Weight in Infants

Factors That Affect Ideal Weight in Infants

There are many factors that contribute to low birth weight of a baby as mentioned below.

1. Inherited Medical Conditions

A baby can inherit potential hereditary diseases in the womb itself, and this may lead to having a low birth-weight baby.

2. Term Completion

Pre-term babies and pre-mature babies are mostly born underweight. This is because the baby did not develop fully in the womb, and since babies put on weight only during the later stages of pregnancy, this stage gets missed.

3. Genetics

Though the mother’s weight actually impacts the weight of the baby at birth, his father’s weight also has some impact. Hereditary forms an equation in the baby’s birth weight. Some babies are simply small as it runs in the family.

4. Age at Conception

For all we know, women after the age of 35 tend to have larger babies. Teen pregnancies generally produce babies who are underweight.

5. Pre-pregnancy Weight

A BMI less than 19 is likely to account for a low-weight baby, whereas a BMI greater than 24 risks the delivery weight of the baby to be quite large.

6. Multiple Births

Babies may be born relatively smaller in case of multiple births as babies share the same uterus.

7. Diet During Pregnancy

Following a poor diet can affect the ideal weight of the infant. So incorporating a proper diet is extremely crucial,

8. Smooth Pregnancy

A smooth and trouble-free pregnancy results in the delivery of babies of optimum weight. Complications during pregnancy can affect the ideal weight of the baby.

9. Medical Issues Before or During Pregnancy

Any sort of medical problems that occur in the fetus during pregnancy can affect the weight of the infant. Pre-pregnancy conditions like anemia, diabetes, renal condition etc. also put the baby to be at risk of being born underweight.

10 Placental Problems

Conditions like pre-eclampsia can reduce the blood supply to the baby, thus restricting the baby’s growth in the womb. Such babies are usually on born low weight because of the deficiency in nutrients and oxygen in the womb.

11. Mother’s Health

If the mother has any unhealthy habits such as drinking and smoking, it may lead to reduced birth weight of the baby.

12. Gender of The Baby

Slight differences between weights might be observed depending on the gender of the baby. Girls are usually smaller and boys heavier.

How Can I Help My Baby Overcome Low Birth Weight?

How Can I Help My Baby Overcome Low Birth Weight?

You must consider the factors that might have contributed to the low birth weight of the baby before concluding anything. Breastfeeding your baby is one of the sure-shot steps for the healthy growth and development of the baby. Diet, family support, love, care and compassion for your little one would do her a great deal of good in development. However, as your baby grows, keep a tab on their weight – some premature babies can gain weight rapidly and be at risk of developing obesity.

Some tips that may help you cope with your low birthweight baby are:

1. Breastfeeding

The best way to nourish and nurture your baby is to breastfeed them as much as he wants. Breast milk is the perfect food for your little one to gain weight and be healthy, though sometimes the doctor may prescribe some vitamins and minerals as well

2. Co-sleeping With Your Baby

Co-sleeping and skin-to-skin contact with your baby would aid in the development of the baby

Click here to read about benefits of co-sleeping with your baby

3. Regular Monitoring

You need to closely monitor your low-birth baby, and reach your doctor if you feel that the baby is developing jaundice, fever, or irregular or laborious breathing

4. Regular Doctor Visits

Low-birth babies need to be vaccinated on time and so regular it is necessary that you visit the doctor well in time. This will also enable to check the baby’s development and growth on a regular basis

5. Limit Visitors

Low birth weight babies have an underdeveloped immune system, hence avoid visitors who are battling an infection, howsoever minor it may sound

6. Be patient

Your baby might be kept in NICU initially to help regulate baby’s body temperature. Be patient and positive during this period

7. Healthy Weight Gain

It might be tempting to give your baby artificial and refined food to help them gain weight quicker. This might not be a good idea. Stick to breastfeeding or formula feeding in the initial 6 months. Even after introducing solid foods, ensure you give nutritious and balanced home-cooked food rather than store-brought cereals that can do more harm than good

If you are pregnant and worried about low birth weight, there are quite a few things that you can do during pregnancy to reduce the risk of a low birthweight baby. These include good and early prenatal care, a balanced and nutritious diet, folic acid supplements and regular health checkups.

To sum it up, it is extremely important to consider the ideal weight for infants seriously as it is a vital indicator of underlying health problems in your little ones. If you want to track the weight gain of your baby, you can follow the baby weight chart which is prepared by pediatricians. Proper diet and regular check-up facilitate ideal weight gain in infants.

Read on factors that influence ideal weight of infants.


1. What Causes Low Birth Weight in Babies?

Premature births are one of the most common causes of low birth weight in babies. Other causes can include the mother’s health during pregnancy, diet habits, drugs and medications used, family history of low birth weight, genetics, etc.

2. Do Low Birth Weight Babies Surive?

The survival of low birth weight babies depend on the weight at birth and the complications associated with the child birth. Babies with weight less than 500 gm are associated with the highest medical complications and the least chances of survival.

Editorial Team,

With a rich experience in pregnancy and parenting, our team of experts create insightful, well-curated, and easy-to-read content for our to-be-parents and parents at all stages of parenting.Read more.

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