Newborns are in most cases long about 50 cm (or 20 inches) and weigh about 2700 to 4000g (6 to9 pounds).
When you visit the doctor he/she will routinely check your weight, heart rate, and sometimes your abdomen, to assess the baby growth. The only way to measure the gestational age is to measure your abdomen from the outside, from the pubic bone to the top of the uterus and the measure is called fundal height. Usually, the number of centimeters is the same as the number of weeks you are pregnant (+-2 or 3cm).
You shouldn’t worry about the greater fundal height, because it usually isn’t a big thing. The bigger fundal height number might indicate you are carrying twins or the baby just moved around in some, you have a larger baby or it is just a mistake in measuring. If the fundal height is smaller than it could be the sign of underdeveloped baby, and that’s when an ultrasound comes handy.
Performing an ultrasound, doctors will measure the body parts of the unborn child and compare these results with the growth charts. This way they will compare the actual size of baby’s limbs and head with the usual sizes in that particular week of the pregnancy and use it to estimate the fetal weight.
Low Birth Weight (LBW)
Usually, babies under 2500g are considered to be underweight. About 10% of these babies are under the gestational age too. Very low birth weight is less than 1500g and extremely low weight baby weight less than 1000g.
Sometimes, the reason for the slow growth of the baby could be the medical condition of the mother. Moms to be who are suffering from high blood pressure can have a baby that is bit slow in fetal growth. Improving mom’s condition leads to improvement of the baby growth, too.
Main causes of the low birth weight are usually preterm childbirth and poor fetal growth. Babies born before the 37 weeks of pregnancy are early delivered, and this is the cause of almost 70% of all LBWs. Other babies with low weight at birth are born at the normal, full term, but haven’t grown as they should be in the womb.
Large for Gestational Age (LGA)
LGA are the babies born with 4000 to 4500g. These babies are sometimes called macrosomia (which is actually a “large body” baby). High birth weight babies are the babies born with more than 4080g, and most of them are also and LGA babies.