Medical advances improve pre-term babies' chances for survival
By Dr. Brigitte Mihalyfi
The Medical Center at Princeton
Friday, Jan. 27, 1998
The McCaughey septuplets who arrived in November nine weeks short of their due date became the most celebrated premature babies in recent times. Of course, the big news was that the entire set of seven survived - a first in medical history. Still, their births did much to publicize some of the more sophisticated means of treating pre-term babies.
There are many premature babies born today who are medical miracles in their own right. Ten years ago, it was thought that 26 weeks was the limit for trying to save a pre-term baby. The normal gestational period is 40 weeks. Now, some babies can be saved at 24-25 weeks and have a decent chance of surviving and having a normal life. However, the limits of viability are constantly debated as technology improves.
The McCaughey septuplets, born at 31 weeks - well past the point where doctors believe fetuses can survive - benefited from one of the newer advances in treating pre-term babies. That is, they were treated before they were born. Their mother was given a pre-birth medication to help strengthen their immature lungs.
This concept of treating the mother before the baby is born has become more mainstream in recent years. Now it has become standard practice to give steroid shots to a mother who has had pre-term labor before or who is in danger of delivering early. The steroids are given once a week, starting at about 26 weeks and not after 34 weeks, when they are no longer effective.
Steroids have made an enormous difference in cutting down on the numbers of babies who suffer from respiratory distress syndrome, or hyaline membrane disease. Respiratory distress is one of the biggest problems pre-term babies face. Their immature lungs often lack a sufficient number of air sacs and a substance called surfactant that helps keep small air sacs of the lung open, so the baby can breathe in oxygen and blow out carbon dioxide.
Steroids also diminish the chances of head, or intracranial, bleeding, another significant complication of extreme prematurity. The cavities within the brain, where spinal fluid is manufactured, are lined with tiny, fragile blood vessels. When these vessels rupture, bleeding occurs.
Another advance in treating pre-term babies is the use of a synthetic surfactant, which the FDA approved over six years ago. Surfactant helps increase the air exchange in pre-term babies either lacking or deficient in the substance. Think of an air sac as a bubble: surfactant helps coat the inside of that air sac so that it doesn't collapse.
Surfactant has become standard care for babies who are less than 32 weeks and 1,500 grams (slightly over three pounds) and who have respiratory distress. It is administered to babies, beginning within the first two hours of life, and may be repeated several times in the first 24 to 48 hours.
Surfactant has vastly improved the survival rate of pre-term infants. It has had the biggest impact on babies between 750 grams and 1,000 grams (about a pound and half to two pounds), usually those between the 26-28 week gestational period.
Over time, pre-term babies will produce their own surfactant and develop more air sacs. A mere week can make a significant difference.
At 24 weeks, the survival rate is approximately 50 percent; at 25 weeks, the rate is approximately 70 percent. Past 26 weeks, the survival rate is often greater than 90 percent.
The problem is calculating that gestational age. Expectant mothers can be mistaken in estimating when they became pregnant, or an ultrasound can fail to pinpoint an accurate gestational age.
Essentially, pre-term babies need a large amount of respiratory support. If a medical team can help a baby get through a few days with minimal respiratory support, and the baby makes his or her own surfactant, the chances for a normal, healthy life are good. For babies who aren't responding well, the respirator may have to be used aggressively, and that sometimes damages the lungs. These babies are the ones who go on to have chronic lung disease.
However, modern medicine is developing improved ways of ventilating the premature infant. The newer respirators aren't as damaging as the conventional ventilator. Respirators used for babies work by delivering a certain amount of pressure to the lungs at specific intervals. If their tiny lungs are stiff because they lack surfactant, they are going to need more pressure to expand the lungs.
The newer high frequency ventilators, of which there are two types, use rates that are several hundred times that of conventional respirators. Therefore, less pressure is needed. The high frequency jet ventilator sends little pulses of oxygen at very high rates, while the other type, the high frequency oscillator, operates at such a high rate you can't even see breath going in and out. It just oscillates and provides an environment where gas can be exchanged. This type seems to work better.
There are also newer means of preventing pre-term babies from becoming anemic, which often happens because of all the blood that is drawn for various lab tests and for monitoring blood gases. Doctors generally do not like giving babies blood transfusions.
In some cases, a synthetic erythropoetin is given to help the baby produce his or her own red blood cells. Erythropoetin is a naturally occurring kidney hormone that is deficient in pre-term babies. The synthetic version of erythropoetin, which is injected under the skin, has been used successfully to treat adults, but doctors have just started treating pre-term babies with it.
During the course of a day, premature babies are subjected to many diagnostic and treatment procedures and that has also led to some changes in the way they are managed. Unfortunately, they get a lot of unavoidable handling, particularly if they are very premature and very sick.
They might have a heel stick several times a day to monitor blood sugar. When they are on a respirator, a central catheter is placed in their belly button to allow the monitoring of their blood gases every few hours. While on respirators, they also need to be suctioned every hour to every few hours.
Neonatologists and the specially trained nurses who care for premature babies try to cluster procedures as much as possible to minimize the distress and stimulation. They also minimize blood drawing as much as possible.
Nevertheless, neonatologists encourage parents to touch their infants. Sometimes doctors have to tell parents that their baby is too unstable and stroking might cause the baby distress. Generally, though, babies actually do better when their parents gently stroke and talk to them.
Most neonatologists always present parents of pre-term babies with the statistics about survival rates and long-term complications. A certain percentage depends on what doctors do, but a large percentage depends on who that baby is. Some babies tend to be more resilient than others. Each infant is different.
Tremendous strides have been made in improving the survival in pre-term babies, but there is still much room for improvement in preventing prematurity. There are several factors that increase the likelihood of having a pre-term baby: poor nutrition, lack of prenatal care, a history of pre-term labor, drug use and diabetes. Fertility drugs also increase the chances of having a premature delivery. The single best prevention of pre-term birth, though, is to get good prenatal care.
Dr. Mihalyfi is a neonatologist on staff at The Medical Center at Princeton. Health Matters appears Fridays in the Lifestyle section of The Packet and is contributed by The Medical Center at Princeton.
Health Matters appears in the Lifestyle section of The Packet and Packet Online. It is contributed by The Medical Center at Princeton.