Odds of Survival for a Premature Baby

According to the March of Dimes, more than 500,000 U.S. babies are born prematurely every year--that’s almost 13 percent of all births 1. Although many preemies make it out of the newborn intensive care unit with no problems, others fight for every breath with undeveloped lungs or experience learning difficulties later in life.


The Mayo Clinic defines a premature birth as taking place at or before 37 weeks of pregnancy 12. A full-term pregnancy lasts at least 38 weeks, with most women giving birth around week 40. Those last few weeks of pregnancy are crucial. According to MedlinePlus, between weeks 31 and 34, a baby gains weight and starts to make breathing movements, but her lungs aren’t fully developed yet, resulting in the breathing problems many preemies face.


The March of Dimes notes that since the 1980s, the number of premature births has increased a whopping 36 percent 1. However, most of this increase falls into the late-preterm subgroup of premature births--babies born 4 to 6 weeks early. C-section births account for most of this surge, but 28 percent of babies are still born between 28 and 33 weeks.

Risk Factors

According to the March of Dimes, some mothers are more at risk than others to deliver prematurely 1. If you’ve already given birth prematurely or are pregnant with twins or triplets, your chances increase. The Mayo Clinic adds that chronic illnesses or harmful behavior patterns can also trigger a premature birth 12. If you smoke, drink, do drugs, eat poorly, have diabetes or have high blood pressure, your risk for a premature birth is higher than usual 12.

Odds of Survival

A study published in the British Medical Journal in 1999 tracked almost four years of premature births in Trent, England--3,760 children in total born between 22 and 32 weeks of pregnancy. According to their results, the overall survival rate was 80 percent. However, the survival rate for babies born before 22 weeks gestation was 0 percent. A study commissioned by the National Institute of Health studied 4,446 babies born between 22 and 25 weeks. Of these, 51 percent survived, but only 21 percent survived without a disability.

Contributing Factors

In the Trent study, the two main contributing factors to survival were age and birth weight. Babies who weighed more than 2.2 lb had significantly higher survival rates--21 percent for 24 weeks and 80 percent for 27 weeks. The National Institutes of Health’s study identified three additional factors contributing to survival: being female, being a single birth and being born to a mother dosed with corticosteroids to encourage fetal lung development 35.

Intensive vs. Comfort Care

If your baby is born at or after 25 weeks, he’ll usually receive aggressive intensive care treatment. However, the National Institutes of Health reports that because the survival rate is so low for babies born before 22 weeks, parents and doctors often decide to provide only comfort care, sparing the baby painful medical procedures that are unlikely to save him.