Is the Prevalence of Down Syndrome Births in Hawai‘i Increasing?

Abstract

Purpose

In response to a study published by the Centers for Disease Control and Prevention (CDC) in 2009, which indicated that the prevalence of Down syndrome births was increasing in the 10 regions studied, this study examined whether a similar trend was occurring in Hawai‘i.

Methods

Data were obtained from the Hawai‘i State Department of : Health Birth Defects Program for the years 1997–2005. The information was analyzed by numbers of live births and outcomes of Down syndrome pregnancies, by ratio of terminations to live births, by age of mother (< 35 years or ≥ 35 years), by maternal ethnicity, and by whether the baby was born with a congenital heart defect (a frequent concomitant condition of babies born with Down Syndrome). These results were compared with previously published studies on the prevalence of Down syndrome births and pregnancies in Hawai‘i and were also compared with recently published data of the CDC.

Findings

The study found that the prevalence of Down syndrome : births for Hawai‘i over the nine-year period did not change significantly. Thus, this finding did not match the findings of the CDC study. Additionally, the data showed that the prevalence of congenital heart defects was higher in Hawai‘i than in other areas. However, because of changes in the resources available to the Hawai‘i Birth Defects Program, fully comparing in all respects data from the 1997–2005 period with studies conducted earlier in Hawai‘i was not possible.

Conclusions

The data identified a number of areas in need of further : study. These areas include the following: 1) an examination of the kinds of information and counseling given by primary care providers to women following a prenatal diagnosis of Down syndrome; 2) analysis of the characteristics, values, and choices made by these women to terminate the pregnancy or continue it to term; and 3) determination of why the prevalence of congenital heart defects appears higher among births of babies with Down syndrome in Hawai‘i than elsewhere.

Introduction

The prevalence of Down syndrome, the most common chromosomal disorder in newborns, has been tracked and analyzed at state and national levels for many years. Many authorities have presumed that, with the increasing utilization of prenatal diagnostic testing, the prevalence of Down syndrome births would decrease. Other authorities, however, have suggested that with births to older women increasing, the prevalence of Down syndrome births would increase.

Previous research in the state of Hawai‘i found that, during the twelve-year period 1986–1997, the prevalence of Down syndrome births remained fairly stable at 8.67 per 10,000 unadjusted live births, but the prevalence of Down syndrome births in Hawai‘i was also lower than reported in other geographic areas.¹ A national study published by the Centers for Disease Control and Prevention (CDC) in December 2009 examined the prevalence of Down syndrome in children and adolescents 0 to 19 years old living in 10 regions of the United States for the years 1979–2003. In contrast to the Hawai‘i data, the national study found that the pooled prevalence of Down syndrome live births had increased by 31% (from 9.0 in 1979 to 11.8 in 2003 per 10,000 live births) with an average increase of 0.9% per year.²

This current study examines data on the prevalence of Down syndrome births in Hawai‘i during the years 1997–2005. These data are compared with the earlier study in Hawai‘i and with the national study to answer the question: Has the prevalence of Down syndrome births in Hawai‘i been increasing, as found in the 10 regions of the United States?

Background

As prenatal diagnostic tools for disabilities such as Down syndrome have become more sophisticated, women and their partners are presented with difficult decisions. Several studies have explored the impact of prenatal diagnosis on the prevalence of Down syndrome and other chromosomal disorders.³ Researchers found that prenatal diagnosis can have an effect on elective terminations and, consequently, the prevalence of a variety of genetic disorders. Findings from one study suggested that elective terminations due to certain birth defects may affect the prevalence by 50 percent or more.⁴

Questions have arisen regarding the role of genetic counseling in assisting women and their partners as they struggle with this difficult decision. While no published research in Hawai‘i has yet addressed this topic, questions arise regarding the kind of information prospective parents are provided. One US mainland study found that, while genetic counseling was helpful, many women said that they were not given information about future quality-of-life issues for persons with disabilities or provided with the positive as well as the negative aspects of giving birth to a child with a disability.⁵ For many of the women who chose to terminate their pregnancy, the decision was affected less by prenatal diagnosis than by their lack of information concerning the quality of life of children with disabilities.

Mothers who chose to continue their pregnancies have expressed dissatisfaction with the information given by their health care providers following a prenatal diagnosis of Down syndrome. A survey of 141 mothers who received such a prenatal diagnosis found mothers who expressed frustration with the process. While satisfied with the medical care they received, the mothers recommended that the diagnosis be conveyed in person, that up-to-date printed materials on Down syndrome be provided, and that mothers be referred to a local Down syndrome support group.⁶

The Disability Rights Movement has become increasingly vocal about elective termination of pregnancies based on a prenatal diagnosis of disabilities like Down syndrome. The movement has called such practices “medical eugenics.”⁷ Such groups make a distinction between reproductive rights and disability rights. While reproductive rights may be viewed as “the right to have an abortion,” disability rights may be viewed as “the right not to have to have an abortion.”⁸ Medical professionals have been accused of failing to communicate correct and unbiased information before and during genetic screening, diagnostic testing, and abortion decision-making. A result is a lack of informed consent and a high abortion rate for fetuses diagnosed with Down syndrome.⁹

The quality of life and opportunities for children born with Down syndrome have increased significantly over the past several decades. Parent advocates cite the potential that children with Down syndrome can lead rewarding and fulfilling lives.¹⁰ Contributing to this potential is the fact that children with Down syndrome have, over the past two decades, benefited from implementation in 1987 of Part C of the Individuals with Disabilities Education Act, which extended services to infants and toddlers with disabilities. Many of the children who experienced the benefits of early intervention are now educated in inclusive classrooms and have opportunities for post-secondary education. Many young adults with Down syndrome are now employed and tax-paying members of their communities.¹¹ Other young adults with Down syndrome have achieved success in many areas. For example, Chris Burke, a young adult with Down syndrome, has been an award-winning actor in a major television series.¹² Other young adults with Down syndrome marry, and some have established careers in the musical arts.¹³

Whether prospective parents of a child with Down syndrome in Hawai‘i are provided with balanced information is uncertain. Few resources have been available to provide such balanced information. To address this lack of resources, the American Academy of Pediatrics developed a tool entitled, “Welcome to Brighter Tomorrows: Supporting Families Receiving a Diagnosis of Down Syndrome.” This tool is intended to give pediatricians, family practitioners, geneticists, and related medical practitioners information to adequately support parents and prospective parents who receive this diagnosis. This is a free resource available online at http://brighter-tomorrows.org.

Methods

In view of the changes that have occurred in opportunities for children born with Down syndrome, and in response to the national data on the reported increase in prevalence of Down syndrome births, this study examined Hawai‘i data to determine if the prevalence of Down syndrome births in Hawai‘i has been increasing. The number of Down syndrome births in Hawai‘i for the years 1997–2005 was obtained to provide a comparison with data from the earlier study in Hawai‘i for 1987–1996 and with the national data for 1979–2003. Additionally, this study was designed to determine if any changes were apparent in the decision to have an elective abortion based on the prenatal diagnosis of Down syndrome compared with decisionmaking in earlier years.

Data for this study were obtained from the Hawai‘i State Department of Health Birth Defects Program and were provided by birth year from 1997 through 2005. The number of Down syndrome pregnancies and births was recorded by year and examined to identify the number and prevalence of Down syndrome pregnancies and outcomes and births per year. Prevalence was calculated by the number of Down syndrome pregnancies and births per 10,000 births per year in Hawai‘i, divided by the number of births.

To determine if the number of pregnancies of babies with Down syndrome was decreasing during this period, the data were analyzed by pregnancy outcomes (terminations, live births, and fetal deaths). The data were further examined by maternal age (younger than 35 years or 35 years and older), and by maternal ethnicity (using the ethnic categories of the Hawai‘i State Department of Health Birth Defects Program). To the extent possible, all of the above data were compared with data from the previous study in Hawai‘i and with the national study.

In addition to the intellectual and developmental disability sequalae of Down syndrome, the National Institutes of Health (NIH) reported that half of all babies born with Down syndrome have congenital heart defects.¹⁴ The previous prevalence report from Hawai‘i did not report the percentage of newborns with Down syndrome who were also identified with congenital heart defects. Therefore, to establish a baseline of published information, the study obtained a frequency count of babies born with Down syndrome who were diagnosed with congenital heart defects.

Results

Prevalence of Down Syndrome Births

Table 1 shows the number of live births and the number of Down syndrome pregnancies for the years 1997–2005. Of 158,790 live births over the nine-year period, 134 babies were identified with Down syndrome at the time of birth. The unadjusted prevalence for the nine-year period was 8.4. The prevalence varied from a low of 5.6 in 2005 to a high of 10.3 in 2002. The total number of Down syndrome pregnancies in Hawai‘i over the nine years was 218 and ranged from 16 to 30 per year; the mean was 22.2. The table also shows the outcomes of these pregnancies. The number of pregnancies that ended in fetal death was 14, with the age of one fetal death unknown. During the period covered by this study, the total number of pregnancies terminated after a diagnosis of Down syndrome was 70, ranging from 3 to 11 per year. The mean number of terminations due to prenatal diagnosis of Down syndrome was 7.7.

Table 1.

Live Births and Outcomes of Down Syndrome Pregnancies in Hawai‘i, 1997–2005

			Outcomes of Down Syndrome Pregnancies
Year	Live Births	Total Down Syndrome Pregnancies	Down Syndrome Live Births	Prevalence of Down Syndrome Births	Fetal Deaths <20 Weeks	Fetal Deaths ≥20 Weeks	Terminations
1997	17,419	30	14	8.0	4	1*	11
1998	17,628	30	18	10.2	0	1	11
1999	17,102	26	15	8.8	0	1	10
2000	17.638	26	16	9.1	0	0	10
2001	17.129	20	10	5.8	2	1	7
2002	17.515	22	18	10.3	1	0	3
2003	18,141	18	15	8.3	0	0	3
2004	18,296	30	18	9.8	2	0	10
2005	17,922	16	10	5.6	0	1	5
Total	158,790	218	134	8.4	9	5	70

^*The age of one fetal death was unknown

Ratio of Live Births to Terminations

In addition to examining the number of births and terminations, it was of interest to compare the ratio of terminations to births to determine if there was an increasing or decreasing tendency over the years for elective termination. The data in Table 2 show that in no year did the number of terminations equal or exceed the number of live births. The ratio of live births to terminations ranged from a low in 1997 of 1.2 live births to 1 termination to a high of 6 live births to 1 termination in 2002. Data are not available on how many mothers with a live birth had received a prenatal diagnosis that their child would be born with Down syndrome.

Table 2.

Down Syndrome Live Births and Terminations in Hawai‘i, 1997–2005

Year	Births	Terminations	Ratio of Live Births to Terminations
1997	14	11	1.2:1
1998	18	11	1.6:1
1999	15	10	1.5:1
2000	16	10	1.6:1
2001	10	7	1.4:1
2002	18	3	6:1
2003	15	3	5:1
2004	18	10	1.8:1
2005	10	5	1.9:1
Totals	134	70	1.4:1

Prevalence of Down Syndrome by Age of Mother

Similar to national data, the percentage of births to mothers age 35 or older in Hawai‘i has continued to increase. The percentage of births to mothers age 35 or older was 15% in 1997. That percentage had increased to 17.6% in 2005.

Table 3 shows that 64 Down syndrome live births occurred among women under 35 years of age, resulting in a prevalence of 4.8. For women age 35 years or older, there were 70 Down syndrome live births, resulting in a prevalence of 26.5. The prevalence for the older group was 5.5 times higher than for the younger group. These numbers were determined based on the total number of live births to all mothers in each of the two age groups.

Table 3.

Down Syndrome Live Births by Age of Mother in Hawai‘i, 1997–2005. (N=Number; P=Prevalence)

Year	Age of Mother				Totals
	<35 years of age		≥35 years of age
	N	P	N	P	N	P
1997	6	4.1	8	30.5	14	8.1
1998	8	5.4	10	35.8	18	10.3
1999	9	6.3	6	21.5	15	8.8
2000	8	5.5	8	26.7	16	9.1
2001	4	2.8	6	20.7	10	5.8
2002	9	6.2	9	31.2	18	10.3
2003	8	5.3	7	22.0	15	8.3
2004	6	3.9	12	38.7	18	9.8
2005	6	4.1	4	12.7	10	5.6
Totals	64	4.8	70	26.5	134	8.4

Prevalence of Down Syndrome by Ethnicity of the Mother

The study also examined the prevalence of Down syndrome pregnancies by ethnicity of the mother during the 1997–2005 period with data from the earlier study in Hawai‘i. Table 4 shows the data. For the current study, the prevalence ranged from a low of just over 8 per 10,000 for African-Americans and Pacific Islanders to a high of 23.9 for Koreans. In the mid-range were Caucasians and Filipinos. Unfortunately, the current study could not compare by ethnicity all the data of the previous study in Hawai‘i. For example, the previous study did not include data on African-Americans, and it grouped Chinese, Japanese, and Korean, under one category, “Far East Asian.” The previous study did not include data on Vietnamese. Likewise, the previous study grouped Hawaiian and Samoan mothers under one category, “Pacific Islander.” Nevertheless, for Caucasians, and Filipinos, the table does show that prevalence of Down syndrome pregnancies in the current study declined from the previous study.

Table 4.

Comparison of Number (N) and Prevalence (P) of Down Syndrome Pregnancies in Hawai‘i by Maternal Ethnicity, 1986-1997* with 1997–2005

Ethnicity*	1986–1997		1997–2005
	N	P	N	P
Caucasian (White)	107	17.6	40	12.6
Black (African American)	(not included)		4	8.4
Far East Asian	92	22.01
Chinese			11	19.4
Japanese			32	16.7
Korean			7	23.9
Vietnamese	(not included)		2	13.9
Filipino	66	15.94	42	13.8
Pacific Islander	58	9.21
Hawaiian			37	8.4
Samoan			4	8.2

^*Does not include the ethnicity category “All Others”

Although the rate of Down syndrome births for Hawai‘i continues to be lower than the national rate, how the state's maternal ethnicity composition contributes to this lower rate is unclear. Unfortunately, the available data did not permit an analysis of the data by the birthplace of the mother or by age and ethnicity of the mother.

Prevalence of Down Syndrome by Congenital Heart Defects

The previous study in Hawai‘i did not report the percentage of newborns with Down syndrome who were also identified with congenital heart defects. However, data were obtained to determine the percentage of Down syndrome babies born with congenital heart defect over the nine-year period of this study and how those data compared with the NIH estimate that half of Down syndrome babies have a congenital heart defect. The CDC national study reported prevalence, not only of Down syndrome births but also of youth to age 19. Since that report used surveillance data, the data cannot be compared with the all results reported in this study. However, the results for Hawai‘i for 1997–2005 are shown in Table 5. Across the nine-year period, three-fourths of all infants born with Down syndrome were also diagnosed with congenital heart defects; this result is well above the 50% rate stated by the NIH.

Table 5.

Babies Born with Down Syndrome and Number of These Babies Born with Congenital Heart Defects (CHD) in Hawai‘i, 1997–2005

Year	Babies Born with Down Syndrome	Also Born With CHD
				Number	Percentage
1997	14	12	86
1998	18	11	61
1999	15	11	73
2000	16	13	81
2001	10	7	70
2002	18	13	72
2003	15	12	80
2004	18	14	78
2005	10	7	70
Totals	134	100	75

Discussion

No definitive trend of either increasing or decreasing prevalence of Down syndrome pregnancies was evident over the nine years of this study. This result (prevalence of 8.4) is similar to the earlier result for Hawai‘i, which showed a prevalence of 8.67 per unadjusted live births over a twelve-year period.¹ This stable prevalence over a twenty-one year period is in contrast to findings of the national study that showed a progressive increase in prevalence, with an unadjusted prevalence of 11.8 in 2003.² The prevalence of Down syndrome birth in Hawai‘i continues to be lower than the national rate.

Further investigation is necessary to examine why such differences occur. As Hawai‘i represents a unique cultural and ethnic composition, further examination is warranted on whether cultural beliefs about raising a child with Down syndrome affect women's decisions to terminate or to continue their pregnancy.

As Table 2 shows, in all years, the number of live births was larger than the number of terminations. The number of terminations was largest in 1997 and 1998 (11 terminations each year). Over the nine years of the study, the cumulative ratio was 1.9 live births to 1 termination. Thus, although with some visible fluctuation, the data show that the number of terminations due to prenatal diagnosis of Down syndrome generally decreased in Hawai‘i during the period 1997–2005. Information is not available on whether the apparent decrease in the number of terminations from 2001 (with the exception of 2004) was a result of decisions to carry pregnancies to term or possibly because fewer women received a prenatal testing resulting in a diagnosis of Down syndrome.

In comparison, the previously reported data for Hawai‘i found an average ratio of live births to terminations at 1.4:1. These live births included both mothers who received a prenatal diagnosis of Down syndrome and those who did not. The national study did not report information on terminations.

The higher prevalence of Down syndrome births among women age 35 and older is consistent with other studies that suggest that as women reach the age of 35 and beyond, the prevalence of Down syndrome births rises dramatically. The prevalence in other studies is lower for both age groups than that reported previously in Hawai‘i.⁴ For the period of 1987–1996, the prevalence of Down syndrome births for women under 35 was 7.2 in Hawai‘i, compared with 4.8 in the current study. For women age 35 or older, the prevalence was 48.3 for the period of 1987–1996, compared with 26.5 in the current study. Therefore, the prevalence of Down syndrome births for both age groups appears to be decreasing.

An additional examination of whether prevalence of Down syndrome births for women 35 and older varies among racial and ethnic populations would be interesting. Also, examining the rates of elective terminations by age group and ethnicity would be helpful. Unfortunately, data were not available to answer these questions at this time.

Comparing these numbers to those previously reported for Hawai‘i is challenging.¹ The prevalence as reported by Forester and Metz covered a twelve-year period, whereas the current study covers only a nine-year period. The data for 1997 were included in both studies. And, as noted above, the earlier study divided ethnicity into the following categories: White, Far East Asian, Pacific Islander, and Filipino. Data were not provided for African-Americans. In addition, the earlier study did not delineate aggregates of the categories Far East Asian and Pacific Islander. Thus, the comparisons of prevalence shown in Table 4 must be interpreted with caution.

The national study did not link ethnicity by birth, but by pooled prevalence from birth through age 19. The race/ethnicity categories used were quite different from Hawai‘i's. The categories in the national study included Non-Hispanic White, Other, Hispanic, and Non-Hispanic Black. Only two of the categories can be compared with the Hawai‘i data. Their pooled prevalence of 10.2 for Non-Hispanic White was lower than Hawai‘i's of 12.6. Similarly, the national data of 7.3 for Non-Hispanic Black was slightly lower than Hawai‘i's 8.4, even though the number in Hawai‘i was quite small.

One finding of considerable interest was the data suggesting that Hawai‘i prevalence of congenital heart defects among infants born with Down syndrome is considerably higher than reported by the NIH. While there were fluctuations in percentages across the years, the percentage for each year exceeded the NIH data. Since these data have not previously been reported for Hawai‘i, further research is needed to determine why the prevalence of congenital heart defects among babies with Down syndrome may be higher in this state than reported elsewhere.

A survey of Hawai‘i's physicians and midwives who deliver babies would be interesting to gather a medical perspective on the kinds of counseling and support services pregnant patients and their partners are provided following a prenatal diagnosis of a child with a disability. Likewise, a qualitative study of women who knowingly give birth to Down syndrome infants each year would be informative to better understanding the circumstances, values, and choices surrounding their decision to continue their pregnancies.

Limitations

A major limitation of the study concerned the limits of available data. As noted previously, earlier studies from Hawai‘i were based on data from the Birth Defects Program. In those years, this program was given an “A” grade from the Pew Environmental Health Commission at the Johns Hopkins School of Public Health and designated as one of the top eight programs in the country, and one of only four programs nationwide to meet all eight rating criteria. Prior to 2006, the Department of Health contracted the program through the Research Corporation of the University of Hawai‘i. In 2006, the decision was made to operate the program directly through the Department of Health.

Following that decision, the Birth Defects Program lost most of its staff and has been without a coordinator. Consequently, data for years after 2005 could not be obtained. Similarly, the data that were available were more limited. For example, data were not available on the outcomes following a positive prenatal diagnostic test for Down syndrome. Thus, a comparison with the earlier study on how many mothers chose to terminate and how many mothers chose to continue their pregnancy to term was not possible.

Conclusions

This study found that the prevalence of Down syndrome births for Hawai‘i over the past nine years has not changed significantly. This finding is not consistent with the national data showing an increase in prevalence of Down syndrome births. Further studies are needed in Hawai‘i to identify what kinds of information and supports are provided to prospective parents when they receive the prenatal diagnosis and how that information may have influenced their decision to terminate or continue the pregnancy. Also important to study is why the Hawai‘i data suggest a higher prevalence of congenital heart defects than the national prevalence.