Tired of explaining your preemie daughter’s size and age to passersby? Indeed, premature infants are smaller in terms of length and weight, but they do put on the ounces and pounds, just like their full-term peers. And keep in mind that the differences between on-time and premature babies are most pronounced in the first year, with the gaps generally closing by age 2 or 2 1/2.
In the meantime, keep up the good work you’re doing feeding-wise, and then check out more about premature weight gain, including the average preemie sizes, the risks associated with low birth weight and some smart ways to help your baby gain a little bit more each day.
What is the average weight of a premature baby?
Premature birth happens in the U.S. in about 11 to 13 percent of pregnancies — and almost 60 percent of twins, triplets and other multiples arrive early too. The average newborn weight of a full-term baby is about 7.5 pounds, depending on race and ethnicity. But late preterm babies born between 34 and 36 weeks may weigh less than 5.5 pounds, which is considered low birth weight.
Infants born between 32 and 34 weeks are called moderately preterm and weigh between 3 and 5 pounds and those who arrive between 28 and 32 weeks (very preterm babies) can range in weight from 2 pounds, 7 ounces at 28 weeks to 3 pounds, 15 ounces at 32 weeks, depending on the sex.
According to the Centers for Disease Control and Prevention (CDC), 8.3 percent of babies in the U.S. were considered low birth weight in 2019 (5.5 pounds), while approximately 1.4 percent of infants were classified as having a very low birth weight or less than 3.3 pounds.
What affects a baby’s birth weight?
A baby’s birth weight can be affected by a variety of conditions in the womb, though the majority are smaller because they’re born prematurely or because they experienced poor growth in utero during pregnancy. Low birth weight is also connected to genetics (if you or the baby’s other parent were petite, your baby may be too), chromosomal abnormalities, heart defects and placental problems.
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Carrying twins, triplets or other multiples frequently also means your babies will arrive at a low birth weight (it’s tight in the womb with more than one baby!), while other factors that can affect weight include gaining less than the recommended amount during gestation, experiencing vomiting in early pregnancy, and smoking, drinking or using (or abusing) certain drugs.
And if you have high blood pressure or heart disease during pregnancy or you’re ill with the flu, syphilis or rubella, it could slow your baby’s growth and subsequent weight gain. Some medications that are prescribed to treat epilepsy, high blood pressure or blood clots can also impact a baby’s size in the womb, so check with your doctor about changing to a safer alternative.
Age can also impact a baby’s birth weight, especially if you’re a teen or older than 35. And unfortunately, access to prenatal care, discrimination, systemic racism and health disparities may affect a baby’s weight too, as can being a victim of domestic violence, whether the abuse is physical, sexual, financial or emotional.
What are the risks associated with premature baby weight?
Babies who are considered low birth weight are much more likely to spend time in the hospital’s neonatal intensive care unit (NICU) for close observation and are more likely to have a range of medical issues, including breathing problems, bleeding on the brain, and a possible heart defect that could need medication or surgery.
Low birth weight babies may also can experience serious difficulties absorbing and tolerating their feedings. And eye trouble is a concern in smaller infants, as is jaundice and the risk of infections due to an immature immune system.
How long does it take for a premature baby to gain weight?
How fast a premature baby gains weight can vary, depending on her starting size and gestational age, and any related health conditions that need treating. But weight gain in premature babies is more of a slow, steady process, rather than a race to pack on the pounds. Preemie babies may gain weight more slowly than full-term infants, but they often catch up in size around age 2.
To help your baby on the best weight-gain path, strive to breastfeed, which often means pumping and feeding expressed breast milk, since it’s the best food for your infant. If you can’t nurse, speak with your pediatrician about the type of formula she recommends. You might also try kangaroo care, which has been shown to help premature babies with weight gain.As you care for your low birth weight baby, try not to stress about how quickly she adds pounds. But if you’re concerned your baby isn’t eating well or enough at each bottle or breast session, you can visit the pediatrician’s office for a quick weigh-in. The doctor is also there to offer feeding tips and much-needed reassurance, especially if you’re a first-time mom.