Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
About Birth Weight
Birth weight is the first weight of your baby, taken just after being born. A low birth weight means that the baby is less than 5 pounds, 8 ounces. A high birth weight means that the baby is more than 8 pounds, 13 ounces.
A baby with a low birth weight can be born too small, too early (premature), or both. This can happen for many different reasons. They include:
- Health problems in the pregnant parent
- Taking certain medicines during pregnancy
- Substance use during pregnancy
- Infections during pregnancy
- Being pregnant with multiple babies
- Problems with the placenta, the organ that brings oxygen and nutrients to the baby
- Having small parents
- Genetic conditions in the baby
- Birth defects
Babies with low birth weight may be more at risk of certain health problems. They include immediate problems, such as:
- Breathing problems
- Infections
- Hypoglycemia (low blood sugar)
- Jaundice
- Trouble keeping warm
There is also a higher risk of longer-term problems, including:
- Delayed motor and social development
- Learning disabilities
- Certain health conditions as an adult, such as heart disease, high blood pressure, diabetes, and obesity
Causes of high birth weight can include:
- Having big parents
- Diabetes in the pregnant parent
- Certain genetic conditions
- Too much weight gain during pregnancy
High birth weight can be a concern because it can make delivery of the baby difficult and raise the risk of birth injuries. The baby is at higher risk of problems with:
- Blood sugar
- Breathing problems
- Jaundice
You may be able to prevent some birth weight problems by:
- Getting regular checkups during pregnancy
- Getting the right amount of nutrition and calories during pregnancy
- Controlling your blood sugar if you have diabetes
- Avoiding substance use during pregnancy
It sits within Children and Teenagers and Pregnancy and Reproduction.
The lead U.S. institute for this subject is the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.
Research on Birth Weight
996 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.
What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.
Research currently under way
- EFFECT OF KANGAROO MOTHER CARE ON HOSPITAL OUTCOME IN LOW BIRTH WEIGHTPakistan Navy Station Shifa Hospital
- Breast-milk Enema Administration to Stimulate Passage of MeconiumWake Forest University Health Sciences
- The PARTUM Trial: Postpartum Aspirin to Reduce Thromboembolism Undue MorbidityUniversity of Calgary
- Using Placental Pathology to Prevent Recurrent Adverse Pregnancy Outcomes: A Pilot ProjectEndeavor Health
- Health Outcomes in C-Section Infants With Fecal Microbiota TransplantationOulu University Hospital
- A Research Study Looking Into How UBT251 Works With Birth Control Tablets and Emptying of the Stomach in Women With Excess Body Weight Not Able to Become PregnantNovo Nordisk A/S
Research already completed
- Multiple Micronutrient Versus Iron-Folic Acid Supplementation in Pregnant Women in IndonesiaIndonesia Timur University
- Efficacy of Intrathecal Administration of Budesonide to Prevent Bronchopulmonary DysplasiaIndonesia University
- Feasibility and Validation of a Smart Changing Pad for Home Infant Weight Monitoring After Hospital DischargeStan Kachnowski
- Donor Milk vs. Formula in Extremely Low Birth Weight (ELBW) InfantsNICHD Neonatal Research Network
- Hearty Meals for Mom- Pilot Study of Meal Delivery for Cardiometabolic Health During PregnancyUniversity of Alabama at Birmingham
- BEP Supplementation Research in Bangladesh (JiVitA-BEP-IR)Johns Hopkins Bloomberg School of Public Health
Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.
Where to read more
Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.
Start Here
- How to Read a Growth Chart: Percentiles ExplainedAmerican Academy of Pediatrics
- Your Newborn's GrowthNemours Foundation
Related Issues
- Fetal Growth RestrictionAmerican Academy of Family Physicians
- Intrauterine Growth Restriction (IUGR)Nemours Foundation
Statistics and Research
- FastStats: Birthweight and GestationNational Center for Health Statistics
Clinical Trials
- ClinicalTrials.gov: Infant, Low Birth WeightNational Institutes of Health
- ClinicalTrials.gov: Infant, Small for Gestational AgeNational Institutes of Health
- ClinicalTrials.gov: Large for Gestational AgeNational Institutes of Health
Medical subject headings
Clinicians and researchers index this subject under Birth Weight. These are the terms to use when searching medical literature.
This page is built from the MedlinePlus health topic record for Birth Weight, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.