The most common cause of low birth weight babies is premature delivery, when the baby doesn't get enough time to grow inside the womb of the mother. The second most common cause is when the baby stops growing inside the womb and no matter what the growth just stops. In this case we need to deliver the baby irrespective of the gestational age.
Talking about premature deliveries, there are several reasons as to why this happens. It can happen due to infections in the vagina of the mother like Group B Streptococcal infections or a recurrent urinary tract infection. These infections start the cascade of reactions which ultimately starts the premature delivery process.
It can also happen if the mouth of the uterus is so short that it cannot hold the weight of the pregnancy and with this pressure it just opens up.
Sometimes it can also happen due to the infection of the womb by the TORCH infections, named so due to Toxoplasmosis, Rubella, Cytomegalovirus, Herpes.
It can also be caused due to some structural anomalies in the uterus like if there is a septum in the middle of the cavity of the uterus or if the cavity of uterus is divided into two parts due to which there is not enough space for the baby to grow inside the womb.
Too much amniotic fluid can also start the process of labor due to excessive pressure.
Sometimes the age of the mother also plays a role, a very young mother, like a teenager, has organs which might not be too well developed to hold the baby till term. Similarly if she is too old then the organs become too weak.
All these factors can lead to preterm delivery and hence low birth weight babies.
Coming to the next part when the baby stops growing inside the womb which is also known as fetal growth restriction, this can happen if the baby is unable to receive proper nutrition either due to the functional abnormality in the placenta (the powerhouse which brings nutrition and oxygen to the baby) or due to abnormality in blood vessels in the umbilical cord (which carries blood from the placenta to the baby).
The abnormalities in the placenta like placenta praevia when part of the placenta is in the lower uterine segment or circumvallate placenta can hamper the growth of the baby.
The reasons for abnormal blood supply through umbilical cord are malnutrition in the mother, drug abuse, smoking cigarettes or drinking alcohol, chronic health conditions like hypertension, advanced diabetes, autoimmune disorders, sickle cell anaemia, chronic kidney disease, obesity and APLA syndrome. All these factors disrupt the blood supply to the baby and hence the low birth weight.
All the above are the maternal factors which can cause low birth weight in the babies. Along with this there are certain fetal factors also which can cause low birth weight in babies like twin pregnancy, fetal anomalies like aneuploidy, triploidy, trisomy 13,18,21, turners syndrome.
Birth of low birth weight babies can cause lots of problems to the babies because they are born when they are not prepared to enter the world. They can suffer from various complications ranging from inability to gain weight due to difficulty in feeding, breathing problems due to immature lungs, bleeding in the brain also known as intraventricular haemorrhage etc.The only way we can prevent low birth weight babies is by ensuring that the mother takes regular antenatal check ups so that the growth of the baby and maternal weight gain can be measured regularly. With this continuous surveillance even risk factors for preterm labor can be minimised. Preventable risk factors like alcohol consumption, smoking and drug abuse should be avoided completely.
(Obstetrician and Gynecologist Amodita Ahuj)
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