What makes a baby big or small? The following are some of the most common causes:
Large Babies: An infant can be born large when the parents are large or the mother is overweight. There is also a greater likelihood of a large newborn due to factors such as:
- The pregnancy lasting longer than forty-two weeks
- The fetus’s growth over stimulated in the uterus
- Fetal chromosomal abnormalities
- Weight gain during pregnancy
- The mother’s ethnicity
- The mother having diabetes before or during pregnancy
- The mother having given birth to other children
- Having a boy
Large infants may have metabolic abnormalities (such as low blood sugar and calcium), traumatic birth injuries, higher hemoglobin levels, jaundice, or various congenital abnormalities. Almost one-third of large babies initially have feeding difficulties. Your pediatrician will keep a close watch on these issues.
Small Babies: A baby may be born small for a number of reasons, including:
- Being born early (preterm)
- Being born to small parents
- The mother’s ethnicity
- Fetal chromosomal abnormalities
- The mother’s chronic diseases such as high blood pressure, or heart or kidney disease
- Malnutrition
- The mother’s substance abuse during pregnancy
A small baby may need to have his temperature, glucose, and hemoglobin level closely monitored. After birth, the pediatrician will thoroughly evaluate a small infant and decide when he is ready to go home.
To determine how your baby’s measurements compare with those of other babies born after the same length of pregnancy, your pediatrician will refer to a growth chart.
Growth charts examine length and weight in boys and girls, from birth to thirty-six months. They are followed by body mass index for age charts for boys and girls, ages two to twenty years. (Body mass index, or BMI, is a measure of weight in relation to height.)
Eighty out of every one hundred babies born at forty weeks of pregnancy, or full term, weigh between 5 pounds 11-1⁄2 ounces (2.6 kg) and 8 pounds 5-3⁄4 ounces (3.8 kg). This is a healthy average. Those above the ninetieth percentile on the chart are considered large, and those below the tenth percentile are regarded as small. Keep in mind that these early weight designations (large or small) do not predict whether a child will be above or below average when he grows up, but they do help the hospital staff determine whether he needs extra attention during the first few days after birth.
At every physical exam, beginning with the first one after birth, the pediatrician will routinely measure the baby’s length, weight, and head circumference (the distance around his head) and will plot them on growth charts. In a healthy, well-nourished infant, these three important measurements should increase at a predictable rate. Any interruption in this rate can help the doctor better detect and address any feeding, developmental, or medical issues.