Ninth Annual Maternal and Child Health Epidemiology Conference / December 10-12, 2003
NANCY GREEN: Thank you, I want to thank the organizers for inviting me on the behalf of March of Dimes and in particular Hani Atrash. Many of you I know collaborate with March of Dimes people at the state and national levels, and so on there behalf I want to thank you all for that. And in particular I know that many of you here collaborate with two of my really wonderful colleagues, Karla Damus, who probably has visited every state this year in her blitz lecture circuit, and the other person is the Head of the Perinatal Data Center Joann Petrini. And actually the Data Center is represented here today by Rebecca Russell who had a poster earlier today and is giving another talk tomorrow.
So anyway I want to thank you and you know as I was listening to the various speakers who preceded me, I kind of deliberated about whether not to tell a joke and what I should say. Because of the problems of time, I am going to just skip the joke, but the truth is that all of my jokes come from my tenure and so they are not that funny, so I am going to skip it. Unless you really press me afterwards and then I might be convinced to tell the latest. So I am going to give you an overview on the epidemiology or prematurity and many of the topics that I am going to pass through quickly are in fact touched appropriately enough by sessions in this meeting, issues of unintended pregnancy, disparities, cesarean sections. So this is really just meant to be an overview and I know that other areas of the meeting covering some of these key points in more detail, okay.
So just for those of you who do not know the mission of the March of Dimes is to improve infant health. And so obviously this group needs no convincing of the importance of the spectrum of reproductive health certainly throughout women’s child bearing years, and through pregnancy, and through infancy and really preconceptional health is a key part of this. So prematurity and certainly much of what I say in a short hand about prematurity is the one thing of prematurity and of birth weight, so I am sure you appreciate. So a preterm delivery is the number one cause of perinatal mortality in the US counting for about 75 per cent of perinatal loss. This is defined as losses between 28 weeks of gestation, and six days of life. It’s the number one cause of neonatal mortality so that is in the first month of life. And the number two cause of infant mortality in the first year of life but for African-Americans because of the really terrible increased burden African-Americans have with preterm low birth weight, it is the number one cause for them of infant mortality. Certainly, preterm delivery, low birth weight is the major determinant of infant and child health. In fact it’s been estimated that about half of all chronic disabilities in childhood can be attributed to prematurity or birth weight, so the impact is huge.
And those illnesses, probably number one are in terms of neurodevelopmental problems with cerebral palsy, mental retardation, learning problems, behavior problems. And I think over the last few years the long-term effects of very preterm, very low birth weight have been increasingly well documented in the literature. Also, respiratory problems, all sorts of infections, growth and development issues, hearing and vision, sort of effecting most organ systems. This is a plug for our Perinatal Data Center Resource, which is a free online Perinatal Data source that could be obtained through the March of Dimes website, you can get national or state data, and it is very beautiful. Actually most of the figures that I am going to show you today were taken from the website so it is very good for presentations and if you have any questions about the website I urge you to talk to Becky Russell. Thanks Becky. As you all know, the rate of infant mortality in U.S. has dropped remarkably in this past 20th Century and we are looks like we are maybe even as sort of asymptote. But if you further dissect the issues, there is much more that can be done and an asymptote is not an acceptable interpretation of the data.
Okay so these are some of the leading causes of infant mortality in U.S. And the light blue is for 1990 and the pink is for 2000 and you can see birth defects, preterm delivery, low birth rates, SIDS, and respiratory distress, which is obviously intermittently linked to preterm delivery are listed here. And you know, this is good news and bad news birth defects, infant mortality rates are way down, but certainly SIDS is you know a remarkable success story. Respiratory distress was a factor during their interventions, but prematurity low birth weight is going in the wrong direction. And I will show you additional data that the incidence is steadily increasing, the disparities are not improving. We are not making progress, so in my next talk, which is I think in another like 20 minutes, when I talk about the March of Dimes prematurity campaign, I have to tell you quite honestly that we entered this campaign with a lot of trepidation. Because you know everybody likes to jump on the train that is moving in the right direction and this we have decided to do quite the opposite. And so you know we certainly speak with a lot of humility about the hope for successes of the campaign, but I think we are very cognizant of the data that I am going to present in this talk.
So certainly, there is big overlap between low birth weight, preterm delivery, and birth defects. And in fact, I know that some of you like Greg Alexander and others are involved with working with Joann Petrini et all and looking at the overlap between birth defects and preterm low birth weight, and I think that is very fruitful area of research. But certainly the point here is that the overlap between the birth weight and preterm delivery is not perfect. And that some of the preterm births are not low birth weight, because of this cutoff at 37 weeks. So you can have reasonably sized infants in the 36, 37th week category. And I will say more about the distribution of gestational ages among preterm births in a moment. So these are the current definitions probably most of you know this, but I will go through it anyway. For birth weight, very low birth weight is less than 1500 g, low birth weight less than 2500 g that is 5½ pounds and for gestational length, prematurity is defined as less than 37 weeks, while very premature is defined as less than 32 weeks. There are also issues of growth restriction, less than 10 percentile for gestational age and that’s all I wanted to say about that in the interest of time. Okay, so here is the bad news headline, which is that you can see, in the light blue preterm births have increased in the country steadily over the last two decades. With the time of best record keeping, from 9.4% in 1981 to 11.9% in 2001, and in fact 2002 data are even less promising the preterm birth rate has gone up to 12% so that is almost 1 in 8 babies. March of Dimes Campaign is, I will tell you about in a few minutes, in my other talk, is to decrease that. And we are certainly very far from the Healthy People 2010 goal of 7.6% unless we get lot more data, lot more interventions, and understanding of mechanisms of preterm birth, not sure we are going to get to those goals.
This is the preterm birth rate by state, drawn in color by tertials. So the highest third are in the dark purple. And as you can see they are largely concentrated in the southeast. Actually somebody in another talk that I showed this slide, asked me if the reason that Georgia is a little bit better, because of his CDC presents, and I did not know how to answer that, but maybe somebody from CDC could help me with that later. Actually, if you line up preterm birth rate by state with percentage of African-American births per state, it is almost a perfect parallel so I think that sadly, the distribution of preterm birth rates largely parallel of the percentage of African-American births in the states. Certainly, the U.S. is way down there in terms of healthy infant outcomes, but preterm delivery rates amongst the developed world. So, even those that are in the Oregon, Washington Montana, the better states, in fact the preterm birth rates are still quite high between 8.2% and 11.2%, so really its still quite unacceptably high. Now, interestingly if you look at the percent change in preterm birth rate over the last decade from ‘91 to 2001, again separated by tertials.
What’s kind of good news and bad news, actually the increase has stabilized or even in one or two states decreased, in some of the states that have had the highest preterm birth rates. And I think that is too a large part to efforts of Maternal Child Health people in terms of increasing access to healthcare for African-Americans and another undeserved peoples. The bad news is that in the states that they have the lowest preterm birth rates, those rates are actually growing very fast, greater than 20% in the last decade, so that is disturbing trend. Now, this is distribution of live births by gestational age in the U.S. in 1990 on the left and 2001 on the right. The lighter purple wedge is the moderately preterm 32 to 37 weeks gestation, and the red is the very preterm, you can see it is very preterm is 1.9% and that has not changed over the decade or so. It is the increase in preterm birth rate, is really at the moderately preterm rate.
And in my talk I am going to talk little bit about why that maybe the case, that the 32 to 37 week gestation are increasing. Okay, so I think this is very interesting data generated by our Perinatal Data Center and that has to do with the gestational age by week in the U.S. for 2001. And the pie is cut up in to gestation weeks, so the biggest slice of the pie, which is the orange at the top is the, those preterm births get 11.9% of the total births. Most preterm births, that percentage status in the 36 weeks, so 37% of preterm births in fact in U.S. are 36 weeks. So, you know one can make the argument that well that is not the optimal outcome, it is not catastrophic and certainly suggested that interventions do not have to be dramatic to improve that. The next sort of largest wedge is the gray on the left, which is 35 weeks and that is little over 20%. So in fact if you add up the 35 and 36 weeks, many of those babies are not low-birth weight as I mentioned earlier, that is about 2/3rd of all preterm births. So really I think what we want to do is target the very preterm, and this is not the real term, but it is sort of intermediate preterm if you will of the 32 to 34 weeks that are represented by various colors here. Okay, so this is preterm birth less than 37 weeks by maternal race or ethnicity and again this is the data that I am sure many of you were familiar with. And that I mentioned earlier that the African-American preterm birth rates are 1½ or some communities two times that of the rest of the population. The native Americans also have a higher than average preterm birth rates and Hispanics are about the same and a little bit lower in the White or Asian those of Wider or Asian background.
Actually, I went to one excellent conference about a year or so ago and you know on disparities in preterm birth, which is you know very frustrating to figure out what it is. Clearly, there are issues of access, maybe issues of lifestyle, or stress or some of the other underlying problems with preterm birth. But the truth is that we really do not know and anyway so somebody stood up and said there is no genetic basis for the differences in preterm births between African-Americans and non-African-Americans. And being a molecular biologist, I got all sort of hot under the collar and said, well I think what you want to say is, there is no single gene involved, likely to be involved in the difference between African-American preterm birth and non-African-American. And that is likely to be a complex interaction of the environment broadly defined and genetics also broadly defined. And I think you know certainly one of the pushes from March of Dimes is in terms of more researches to understand the pathways of preterm delivery, but also to better dissect out those factors genetic and environmental that impact gestational length. Okay, thank you. I do not have time for making jokes at the end. So this pie chart is just a distribution of preterm births in U.S. by race and ethnicity. The blue at the bottom is non-Hispanic White. And what you can see is that certainly the percentages of all birth, live births in U.S. for non-Hispanic/White population is 57% and the percentage of preterm birth in U.S. is a bit lower at 52%, again just reflecting the demographic that I showed you earlier.
So the punch line over the side is that this is the problem that affects every community that is really national problem. I do not have time to go through this, but preterm birth is a combination of spontaneous and indicated preterm birth, and I am going to talk about that in a second. This I have to admit it is slide from Karla Damus more for than I can actually read off. She talks a lot faster than I do, so she could do it, but certainly the best predictors of preterm birth are our previous history. Preterm birth and in fact maybe there is a little bit of progress may there is recent maternal-fetal-medicine that works steady on use of progesterone on some of those patients. Multifetal pregnancy and I am going to talk about that in a second and certain uterine and cervical abnormalities. And then there is a whole host of socioeconomic and demographic factors, issues of healthy life style including nutrition and weight and smoking, which I do not have time to go through. But certainly the bottom line here is, we don’t know a lot, and in terms of thinking about this in terms of a risk reduction, it is going to be multifocal and do what you can do. And I feel that this group needs no convincing of that, when she prevents, what is preventable.
Okay, why do we have an increased rate of preterm birth in the U.S. you know much of this we do not know, that we do know is that there is an increase of rates to woman greater than 35. They have an increased rate of multiple births, some of those are spontaneous and some of those were through assisted reproductive technology and now CDC, in particular has been very productive in analyzing the impact of ART on birth outcomes. Some of this indicated deliveries have to do with better management, maternal-fetal monitoring and better medical management, and some of them may have to do with issues of cesarean section, and another kinds of consumer interest. Issues of substance abuse and then this hotchpotch of stress, which I do not like to talk about because I do not know what it means, but it seems to be of prevalence in the literature about an importance of stress. And I know some of you here, are involved in the research on that important topic. This is data on the increase of maternal age in the U.S. and the red and on the top is, line that is going up is 30-34 year old mothers, the yellow in the middle is 35-39 year olds, and the bottom is the 40-44 year olds. And you can see that amongst the older women, the rates were going up. And this is important for preterm birth because preterm delivery rates are on higher at the extremes, less than 17, 18, and over 35 and certainly over 40. Against the 40 year old, some of these has to do with technology and some is spontaneous and similarly with very pretermed sort of average in the middle and then higher on the extremes of age.
The plurality issue is huge, again this has to do in parts with ART. The preterm birth rate for singletons is 10.4%, for twins is over 50%, and for triplets and higher is over 90%. So the fact that they are now 3.2% of all births in the U.S. are multiples, that has a huge impact on prematurity rates overall and also infant health. And I am going to zip through this. Just to say that the White rates for multiples are increasing faster than the African-American rates and the higher order the triplets in higher are leveling off, again probably having to do with an increased scrutiny and evolving set of practices around ART. And in fact, ART is important because some are between 10% and 35% of life births from ART are twins. And a lower percentage, but substantial for triplets, even the singletons have increased risk of preterm birth and low-birth weight. And they have an increased rate of birth defects, about a two-fold rate, but whether it is the procedure or the parents or some combination really needs to be studied further. I am going to finish.
A preterm birth, singleton preterm birth rates are also increasing, but it came at a lower rate than the birth rate of 6.1% in the last decade. And some of these again has to do a cesarean practices and I just want to show you that these cesarean sections, both primarily and repeated are on the way up and a lot has to do with the patient preference. And in fact, ACOG recently came out with an ethical guideline. Basically saying that if women insist upon a cesarean section despite no medical indications, ethically that maybe really okay. I guess, I have some concerns about the trends of cesarean sections as evidence by this for singleton preterm or else you can see that the higher rates of preterm birth were due to section. Again some of these maybe indicated, but some of them may not be, and so I think it is an area that needs some more study in terms of optimizing messages to patients and policy. So, I think that’s it. Yeah, and thank you very much, and I want to just acknowledge we have a Grand Rounds Program that helps support March of Dimes sponsors lectures nationwide, and it is supported by the Johnson & Johnson Pediatric Institute, so thank you for your attention.