Low Birth Weight Babies

Dr. Parang Mehta, MD.

The birth of a baby is usually an occasion of great joy for the family.  For the medical team looking after the pregnancy, too, the birth of a healthy, normal baby is a matter of great satisfaction.  One of the greatest killjoys is the birth of a tiny baby -- a baby born early (premature), or full term, but of low weight because of poor growth in the womb.

Small babies, whether premature or IUGR, are prone to a large number of problems.  These can be very serious, threatening the very survival of such babies.  Many small babies do not survive the first month of life, though good medical care can save many of these high risk babies today.

Problems with being premature

Most small, or low birth weight, babies are borm prematurely.  These babies have not had an adequate period of time in the womb to mature fully.  The lungs, liver, digestive system, and other systems are often not fully ready to start functioning at birth.  The immaturity of these systems creates several problems in the first few days after birth.

Babies get a lot of anti-infective antibodies from their mother.  This transfer of antibodies across the placenta occurs mostly in the last 6-8 weeks of pregnancy.  Thus, premature birth deprives the baby of this valuable resource, and they get infections easily.

Low birth weight babies also have low reserves of energy.  The are prone to hypoglycemia (low blood sugar levels), hypothermia (low body temperature), and other metabolic problems that can leave a permanent effect.

Early problems of LBW babies

Some terms related to small babies

Full Term: A baby born after at least 37 weeks of pregnancy.  The first day of the last period is taken as the initial date.  While a normal pregnancy is taken as 40 weeks (280 days), 37 to 42 weeks is the range for a normal duration.  

Preterm/ Premature baby: A baby born before 37 completed weeks of pregnancy is considered a premature/preterm baby.  These babies have not had adequate time in the womb to grow fully, and for all their organ systems to mature.  They face several problems in adapting to life in the outside world.

IUGR/ SGA/ SFD: These babies have not grown appropriately in the womb.  They are lighter at birth than normal babies with an equal length of pregnancy.
IUGR: Intra Uterine Growth Retardation.
SGA: Small for Gestational Age.
SFD: Small for Date.

LBW: Low Birth Weight babies are those that weigh less than 2.5 Kgs (5.5 lbs) at birth.  The low birth weight may be cause by prematurity, IUGR, or a combination of both.  Low birth weight is usual with multiple birth (twins, triplets, etc), but that does not lessen the risks, of course.

VLBW: Very Low Birth Weight babies are those that weigh less than 1.5 Kgs (3.3 lbs) at birth.  These babies often have serious problems soon after birth, and many of them do not survive.

Long term problems of LBW babies

Last Revision: May 12, 2020