We review special considerations that must be taken for late preterm infants. We are joined by Rashmin Savani, MBChB, Professor and Chief of the Division of Neonatal-Perinatal Medicine at the University of Texas Southwestern Medical Center.
Dr. Neeta Goli:
Welcome to Newborn News, a podcast where we discuss educational topics for medical professionals who care for newborns. I'm your host, Dr. Neeta Goli, a pediatrician in the UT Southwestern Newborn Nursery. Welcome back to the podcast. Today, we'll be discussing the care of late preterm infants. We're joined today by Dr. Rashmin Savani, the Division Chief of Neonatal and Perinatal Medicine at UT Southwestern. Thanks for joining us today.
Dr. Rashmin Savani:
Great to be here.
Dr. Neeta Goli:
So let's start with the basics. What do we mean by term, preterm, and late preterm?
Dr. Rashmin Savani:
Of course, the terminology in this area has been very confused over the years. We've had quite a few names, marginally preterm, or moderately preterm, even mildly preterm, which I find surprising, of course. And then near term or almost term, I think we've settled down with the categories of late preterm infants and early term infants. And there's a good definition of that, so that if you are between 34 and 36 and 6/7ths, you are a late preterm infant. If you are 37 to 38 and 6/7ths, you are now an early term infant. And then if you get above that and go on to 41 and 6/7ths, you are now a late term infant. And I think it's important to define that because it looks like the optimal time to be born is around 39 to 40 weeks. And even if you are a week earlier, we might think of that as term, but they still have complications that can occur.
Dr. Rashmin Savani:
The rate of late preterm birth has increased over the years from about 7.3% to 9% between 1990 to 2006, and accounts for 84% of the entire rate of prematurity increase over that time. And that's really based on boutique deliveries. So that mom says, "I need to go on vacation. I need to have my birth next Friday morning, please." And, the obstetrician says, "Actually, I'm going away. I'm going on conference or whatever we're going to deliver you on such and such date." Rather than waiting for the natural labor to start. And I think that a lot of these boutique deliveries were happening in the late nineties and early two thousands. And it wasn't until we appreciated the fact that being just a late preterm or an early term infant has consequences for you that the no elective delivery before 39 weeks came about, and we have to thank the March of Dimes and the American Academy of Pediatrics and other organizations for really championing that cause.
Dr. Neeta Goli:
So why are late preterm infants different from the rest of preterm infants?
Dr. Rashmin Savani:
So late preterm infants are unique because when I was growing up as a neonatologist, many moons ago, some of these infants, a lot of these infants ended up in the NICU. As our newborn care has improved, or as our newborn nurseries have improved, if you're a late preterm infant, 35 weeks and above, you actually end up in the normal newborn nursery. So these infants are not term babies, not even early term babies. And they're now in the normal newborn nursery, where there are a lot more babies, the staffing ratios are different so that one nurse will be taking care of several babies. And so they are appropriately observed less stringently, in the newborn nursery, but you have to identify the babies that are late preterms or early terms, because they're the ones who can have more difficulties. So we need to pick out the babies that are having problems in the newborn nursery. So that's where the real problem starts is that these babies are now well enough to go to the normal nursery and can have difficulties there.
Dr. Neeta Goli:
And how might they be different from the other preterm babies who remained in the NICU?
Dr. Rashmin Savani:
So the preterm babies of course have far fewer stores. They are immediately recognized as being preterm so that we don't anticipate they will feed properly and we'll need tube feedings and maybe IV support, et cetera. Whereas the late preterm infants, they look well and they look healthy and their APGAR scores are great and they ended up in the normal nursery. So it's important to recognize that the NICU will take the babies that are preterm and appropriately observe them carefully, et cetera, but we need to be careful about the late preterm infants and the early term infants that end up in the newborn nursery, where they could have complications. And there may be a delay in identifying them.
Dr. Neeta Goli:
What kind of complications should we watch out for?
Dr. Rashmin Savani:
So the surprising thing for me was to look at the rates of different complications in term versus late preterm infants. And if we take, for example, respiratory distress syndrome, the incidence of respiratory distress syndrome at term is about 0.1%. At 35 to 36 weeks, it's 2%. So that's a 20 fold increase in the rate of RDS. So while 2% is not that big a number, the fold increase is huge. So they don't behave like term infants. Of course, if you're 33 to 34 weeks, the incidence is about 10 to 12%. For example, transient tachypnea of the newborn: in term babies incidence is about a 0.5 to 0.7%. In late preterm infants, it's 5%. So there's almost a 10 fold increase in the incidence of TTN. Apnea for example, is zero in term babies. We never see apnea in term babies, unless they have some genetic disorder, of course. But late preterm infants, the risk of apnea can be 4 to 5%.
Dr. Rashmin Savani:
And these are babies sometimes that get discharged at two days from the normal nursery and end up having apneic episodes at home and then get readmitted with acute life threatening events. Other things that can go wrong are temperature instability: the more preterm you are, the more difficulty you have in controlling your temperature. This doesn't appear to happen with normal clothing and wrapping of term babies, but it can be as high as 10% in late preterm infants.
Dr. Rashmin Savani:
And the hyperbilirubinemia that occurs preterm infants, obviously don't have as well developed a conjugation system, et cetera, to deal with increased bilirubin load that happens after birth. And so the late preterm infants will have a higher incidence of hyperbilirubinemia, such that term infants will have almost no delayed discharge due to hyperbilirubinemia. Whereas up to 15 to 16% of late preterm infants will have prolonged jaundice that would delay their discharge.
Dr. Rashmin Savani:
We've talked about hypoglycemia. These babies clearly will not feed properly. They have fewer stores because they're smaller and they can have increased risk of hypoglycemia. So there's a fourfold increase in the risk of hypoglycemia in late preterm infants compared to term infants.
Dr. Rashmin Savani:
One surprising thing about increased morbidity in late preterm infants is that their mortality is increased. So their rate of mortality, of course, in term infants is extremely low, but when you measure it in late preterm infants, you can get a two to five fold increase in the mortality in these infants.
Dr. Neeta Goli:
What should parents expect when their babies grow up in terms of outcomes later in life for late preterm infants?
Dr. Rashmin Savani:
Yeah, this is the statistic that I found most shocking. The incidence of IQ scores less than 85 is increased in infants that are late preterm infants. So a full scale IQ, for example, can be less than 85, four fold higher incidence of that. And in performance IQ testing, it can also be about a four-fold increase of abnormal findings. There's also an increased incidence of social, emotional problems, so that they have problems with internalizing, externalizing, attention problems. And this is all increased in late preterm infants.
Dr. Rashmin Savani:
These can result in anxiety, depression, somatic complaints and withdrawal, as well as long-term aggression and delinquency. So, adolescents that have these long term, psychological and psychiatric problems, one should be wise and get a history of what happened at birth. Were they actually a late preterm infant? And that might explain some, if not all, of the aggressive behavior that is being observed in adolescents.
Dr. Neeta Goli:
Are there anything that we as clinicians or parents can do to mitigate these morbidities?
Dr. Rashmin Savani:
So obviously, decreasing the rate of preterm birth would be wonderful. We have made great strides in decreasing the rate of preterm delivery and an initiative to have no elective births less than 39 weeks I think was instrumental in decreasing the rate of prematurity in this country. Although we still find that some of that still goes on, there's great data, for example, in a pre and post studies that were done before the institution of 39 weeks as a cutoff date for elective deliveries. Once that study by Oshiro in 2009, showed that the elective deliveries before 39 weeks in the period one, which was the pre cohort occurred in 28% of pregnancies, which is quite high. And that, of course by definition, when they instituted no elective deliveries before 39 weeks, fell down to 3%. So clearly 25% of those deliveries didn't need to happen before 39 weeks.
Dr. Rashmin Savani:
That had consequences so that the rate of Cesarean section was almost doubled. Neonatal morbidities were increased, such that meconium aspiration syndrome was higher in the ones that were delivered before 39 weeks. Respiratory distress syndrome appeared to be about the same and the incidence of mechanical ventilation appear to be about the same. But the rate of stillbirth for example, was increased nine fold. It was only 0.09%. That's an extremely low number, but it was nine fold higher than what occurs if you waited until 39 weeks. So, it had profound effects on the nature of outcomes for these babies just to stopping and not delivering electively before 39 weeks.
Dr. Rashmin Savani:
So for example, our own hospital, Parkland Hospital instituted the no elective delivery before 39 weeks, 20 years ago. And consequently, at the time when the United States preterm birth level was going up, between 1995 and 2002, the rate of prematurity at Parkland actually fell by 50%. And so Parkland's prematurity rate still remains lower than the national averages, mainly from good prenatal care, adequate addressing of all prenatal issues and the prevention of elective births have before 39 weeks.
Dr. Neeta Goli:
So, once we have these late preterm babies who we're taking care of what special precautions should we take?
Dr. Rashmin Savani:
Well, the first thing is to make sure we identify the babies, right? We've talked about the fact that the incidence of late preterm births having problems is quite small. So even if you have a 2 to 5% incidence, we have to identify those patients first. So it's important to identify those that are at risk. So when we are looking at maternal histories and what happened to the babies at the time of birth, a younger gestational age, for example, so if you're more 35 weeks compared to 37 weeks, you're likely to have more difficulty. If you're small for gestational age that increases your risk of problems. If you're a multiple gestation, those babies are usually acting more premature than their gestational age would suggest.
Dr. Rashmin Savani:
For instance, if they did not have antenatal steroids, and past 34 weeks, we don't give antenatal steroids. So it's important to know whether they got antenatal steroids or not. They may have had an elective cesarean delivery and that sometimes happens before 39 weeks. So if that was an elective C-section before 39 weeks, that's a baby you ought to be more careful with. So in looking at all the risk factors that might contribute for a baby becoming a late preterm infant, we can use those to identify the babies that we need to observe more closely. And it's really incumbent on the newborn staff to do that.
Dr. Rashmin Savani:
In managing the situation, it's important that good communications occur between the pediatrician and the obstetrician that counseling between those two and an accurate determination of what the gestational age is, is really important. We know that if you determine gestational age in the later part of pregnancies, it can be wrong up to two weeks in error, and that can make a huge difference if you're a preterm infant. If you're born at 35 weeks, you could be 37, or if you're born in 37, you could actually be a 35 weeker. So it's important to get the gestational age correct. Last menstrual period or early ultrasound, growth trajectories, and growth measurements can give you the best hope of getting a good assessment of what the gestational age is.
Dr. Rashmin Savani:
These discussions between OB and pediatrics can limit or eliminate the elective deliveries before 39 weeks. And we should have appropriate admission criteria for the NICU. So if some criteria are met, then those babies get transferred to the NICU so that they can be watched even more closely if need be. We're obviously don't want every baby going to the NICU because we don't have NICUs that big. So triaging patients, making sure we looked at the ones that are at risk, and then the ones that are having quite significant problems can be transferred to the NICU.
Dr. Rashmin Savani:
Watching feeding closely would be really important; these babies are at higher risk for getting dehydrated and becoming hypoglycemic. Following transcutaneous bilirubins of course is very important, and then watch for signs of apnea or distress. A really important thing is to counsel the parents before sending this baby home. They need to know that while the physiologic transition has occurred and the APGAR scores were fine, that this baby merits a little more closer watching and a quicker reaction if something amiss happens. So if the baby is cold or has feeding difficulties, we should ask them to seek the pediatrician's help more quickly than if they'd been a term kid greater than 39 weeks.
Dr. Neeta Goli:
Dr. Savani thanks so much for joining us for this great talk today. To end today's episode, what tips do you have for success for our listeners while they're taking care of newborns?
Dr. Rashmin Savani:
Well, it's always good to be vigilant, assess risk factors, and be proactive in identifying babies at higher risk. Institute prompt interventions, and with appropriate criteria that you can develop with your NICU and with your obstetricians; you can successfully have healthy babies in the normal newborn nursery and only transfer the ones that really need to get transferred to the NICU, because we obviously want to be taking care of sick babies in the NICU, not well ones. So I think good communication within all parts of your system and appropriate triage criteria that have been developed is the best way to take care of babies.
Dr. Neeta Goli:
Thanks so much for joining us today.
Dr. Rashmin Savani:
It's been great, Neeta, thanks.
Dr. Neeta Goli:
Thanks for listening to Newborn News. We hope you join us next time. If you like what you hear, make sure to subscribe and leave us a review. If you have questions, comments, feedback, or suggestions for future episodes, please email me at NewbornNews@utsouthwesternat.edu. As a reminder, this content is educational and is not meant to be used as medical advice. Views or opinions expressed in this podcast are those of myself and my guests and do not necessarily reflect the views of the university.