Dr P K Nath

A low birth weight baby we delivered at NBMCH.

LBW is either the result of preterm birth (that is, a low gestational age at birth, commonly defined as younger than 37 weeks of gestation) or of the infant being small for gestational age (that is, a slowprenatal growth rate), or a combination of both.

Preterm birth: different pathways have been identified that can result in preterm birth and have considerable evidence: precocious fetal endocrine activation, uterine overdistension, decidual bleeding, and intrauterine inflammation/infection.

Small for gestational age: Being small for gestational age can be constitutional, that is, without an underlying pathological cause, or it can be secondary to intrauterine growth restriction, which, in turn, can be secondary to many possible factors. For example, babies with congenital anomalies or chromosomal abnormalities are often associated with LBW. Problems with the placenta can prevent it from providing adequate oxygen and nutrients to the fetus. Infections during pregnancy that affect the fetus, such as rubella, cytomegalovirus, toxoplasmosis, and syphilis, may also affect the baby's weight.

Environmental factors: active maternal tobacco smoking has well established adverse perinatal outcomes such as LBW. Mothers who smoke during pregnancy are twice as likely to give birth to low-birth weight infants. Passive maternal smoking also increases risks of infants with LBW. Researches have shown that elevated blood lead levels in pregnant women, even those well below 10ug/dL can cause miscarriage, premature birth, and LBW in the offspring. 

The combustion products of solid fuel in developing countries can cause many adverse health issues in people. Because a majority of pregnant women in developing countries, where rate of LBW is high, are heavily exposed to indoor air pollution, increased relative risk translates into substantial population attributable risk of 21% of LBW.

A correlation between maternal exposure to CO and low birth weight has been reported that the effect on birth weight of increased ambient CO was as large as the effect of the mother smoking a pack of cigarettes per day during pregnancy. Mercury is an known toxic heavy metal that can harm fetal growth and health, and there has been evidence showing that exposure to mercury (via consumption of large oily fish) during pregnancy may be related to higher risks of LBW in the offspring.

It was revealed that, exposure of pregnant women to airplane noise was found to be associated with low birth weight. Aircraft noise exposure caused adverse effects on fetal growth leading to low birth weight and preterm infants.

Effects: LBW is closely associated with fetal and Perinatal mortality and Morbidity, inhibited growth and cognitive development, and chronic diseases later in life. At the population level, the proportion of babies with a LBW is an indicator of a multifaceted public-health problem that includes long-term maternal malnutrition, ill health, hard work and poor health care in pregnancy. On an individual basis, LBW is an important predictor of newborn health and survival and is associated with higher risk of infant and childhood mortality.

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