Section VI - Current Topics

NTD Surveillance and Prevention

The prevention of neural tube defects (NTD) by folic acid has been one of the most exciting events in the area of birth defects. The primary prevention of the occurrence of a birth defect rather than secondary prevention through termination is very gratifying. However, tracking the effects of folic acid on trends in NTDs is difficult and cannot be done easily by most registries at present. Many NTD affected pregnancies are detected prenatally as a result of ultrasound or AFP screening. One study from the Centers for Disease Control and Prevention (CDC) found that about 40% of NTD cases are detected prenatally and terminated and the percent of terminations increased over time2. Tracking trends in livebirths of NTD cases will not be very useful for surveillance of trends in the actual occurrence of NTDs. As discussed in our report for the 1992 birth cohort, NTDs appear to be declining in New York State but the CMR receives reports primarily on livebirths.

CMR Neural Tube Defect Surveillance Project

New York State has in place a regional NTD surveillance project using active case ascertainment. This project was developed through funds from a three-year CDC cooperative agreement. Beginning in 1996, active surveillance of NTDs has been carried out in the seven counties of the Lower Hudson Valley (HSA 6), an area with about 30,000 annual births. A surveillance system has been established using hospitals, radiology facilities, health care providers and termination facilities. Cases were collected retrospectively back to 1990 and prospective case ascertainment began in the spring of 1996.

Active collection of NTD cases in HSA 6, including prenatally diagnosed cases, has clearly shown the advantages over the passive ascertainment of the CMR (see Table 1). For 1990 through 1997, 91 cases were reported to the CMR, while the surveillance found 167. More than 18% of liveborn cases from 1990 to present were not reported to the CMR. None of the stillborn/terminated cases were reported to the CMR. Further, there were a significant number of cases reported through the CMR which, upon review, were excluded because they did not meet case criteria. These included cases erroneously coded with ICD codes corresponding to NTDs, which were clearly not NTDs upon review of medical records.

Table 1
Number of cases of NTD by Year of Birth, 1990-1997, HSA 6
CMR Neural Tube Defect Surveillance Project
(Number of cases of NTD reported to the CMR from HSA 6
  1990 1991 1992 1993 1994 1995 1996*+ 1997
Anencephaly 6 (1) 6 (2) 5 (2) 9 (4) 9 (2) 4 (0) 11 (0) 5 (0)
Spina bifida 12 (11) 13 (12) 13 (11) 8 (4) 9 (8) 10 (6) 10 (8) 7 (2)
Encephalocele 7 (5) 7 (7) 3 (1) 1 (1) 3 (2) 3 (0) 4 (2) 2 (1)
Total <25 (17) <26 (21) <21 (13) <18 (9) <21 (12) <17 (6) <25 (10) <14 (3)

* Prospective surveillance began May 1996
+ CMR reporting incomplete

Table 2
Annual Occurrence of Neural Tube Defects*
CMR Neural Tube Defects Surveillance Project
Lower Hudson Valley, 1990-1996
Year Anencephaly Encephalocele Spina bifida Total
90 0.19 0.22 0.38 0.78
91 0.19 0.22 0.41 0.83
92 0.16 0.10 0.42 0.68
93 0.30 0.03 0.26 0.60
94 0.30 0.10 0.30 0.70
95 0.13 0.10 0.33 0.57
96** 0.37 0.14 0.34 0.85
Total 90-96 0.23 0.13 0.35 0.72

* Per 1,000 live births.
** Prospective surveillance began May 1996.

Although there is some variation from year to year, probably due to small numbers, overall the occurrence of NTDs appears to be stable (Table 2). The occurrence of the individual malformations also appears to be stable with a possible decline in encephalocele and increase in anencephaly. However, both of these apparent variations could result from small numbers or variable case ascertainment.

Table 3
Percent of NTD Cases Terminated
CMR Neural Tube Defect Surveillance Project
Lower Hudson Valley, 1990 to 1998
  Anencephaly Encephalocele Spina Bifida Total
90 50.0 14.3 8.3 20.0
91 67.0 14.3 7.7 23.1
92 20.0 33.3 7.7 14.3
93 55.0 0.0 37.5 44.4
94 33.0 33.3 11.1 23.8
95 100.0 66.7 20.0 47.0
96* 36.0 25.0 30.0 40.0
97 100.0 50.0 42.8 64.3
98** 100.0 0.0 33.0 60.0
Total** <54.0 <26.7 <21.2 <33.1

* Prospective Surveillance began May 1996.
** Includes first 3/4 of 1998.

The overall percent of NTD cases terminated increased from 20% in the early 1990s to 40 to 60% in the later years. This was most marked for anencephalic cases which went from about 50 to 100%. However, there has been a noticeable increase in termination of spina bifida cases from less than 10% in the early 1990s to about 33% in the late 1990s. This again illustrates the need for surveillance to include terminated cases to be able to see true declines in occurrence of NTDs.

As expected, prenatal diagnosis of NTDs has substantially affected the birth prevalence. Between 1990 and 1996, 31% of all NTDs were electively terminated, and an additional 8% were stillborn or spontaneously aborted. The live birth prevalence of NTDs during this period was 0.45/1,000 live births. However, when including the cases that have been electively terminated and those that were stillborn and spontaneously aborted, the total prevalence rises to 0.72/1,000 pregnancies. No cases of anencephaly have been reported to the CMR from HSA 6 since 1994. Tables 2 and 3 present data from this surveillance system. Using this surveillance system the CMR will continue to monitor the occurrence of NTDs.

Knowledge and Use of Folic Acid

The major factor in primary prevention of NTDs is whether or not women of childbearing age know about and use folic acid before they become pregnant3. National data suggests that more education is necessary4. In a March of Dimes survey carried out by the Gallup Organization, 32% of women of childbearing age took folic acid supplement daily. However, only 13% knew folic acid helps prevent birth defects and 7% knew it should be taken before pregnancy.

The Department of Health's Bureau of Community Relations has an active folic acid campaign. In the Fall of 1996, this Bureau launched a professional educational campaign on folic acid. This was repeated in fall 1997. By spring 1998, nearly one million pieces of educational materials including brochures available in English, Spanish, Chinese and French, as well as grocery list pads, fact sheets, resource lists, tray inserts, etc. were distributed. DOH has also forged partnerships with other health-related professional groups, as well as grocery market chains, who have distributed their own educational materials on folic acid, as well as reprinting and distributing DOH-produced folic acid materials. The state's folic acid campaign has drawn praise from the CDC, FDA, and other states. DOH has also advised other states concerning their creation of folic acid campaigns. Despite these efforts, data from two systems suggest that educational efforts are still needed.


The Pregnancy Risk Assessment Monitoring system (PRAMS) is a CDC sponsored program which supplements birth certificate data by conducting surveillance of maternal behaviors during pregnancy5. Table 4 shows responses from pregnant women who had a live birth in 1996.

Table 4
Percent of Women Who Had Heard that Taking Folic
Acid Reduces the Risk of Some Birth Defects by
Maternal Characteristics
PRAMS 1996
Maternal Characteristics Percent

     => 30

     <High School
     High School
     >High School
Medicaid Status
     On Medicaid
     No Medicaid
Total 67.9

Many minority women, younger women, women with less education and lower SES women have not heard about folic acid reducing the risk of birth defects. This does not indicate how many women actually took folic acid before the pregnancy.


Another source of information on the knowledge and use of folic acid among New Yorkers is the Behavioral Risk Factor Surveillance System (BRFSS). The BRFSS is a CDC sponsored program. A random sample of New Yorkers are surveyed regarding their health behaviors.

These tables show BRFSS data collected in 1997 for women of childbearing age. Table 5 shows the percent of women 18-45 who say that they take vitamins and know that the vitamins contain folic acid. Overall, about 30% of women reported that they knew they were taking vitamins with folic acid. Since almost 55% of women reported they took some vitamins, the percent of women taking folic acid might actually be higher. The percent of women who knew that they took folic acid varied by maternal characteristics. The percent was lower for minority women and women under 24 years. Women with higher levels of education were more likely to know they were taking folic acid. Women with health insurance other than Medicaid were also more likely to know they were taking folic acid. Only about 19% of women on Medicaid know if they were taking folic acid.

Table 5
Percentage of Women Who Take Vitamins and Folic Acid BRFSS, 1997
Age Yes, take Vitamins Yes, take Folic Acid
18-24 51 20
25-29 51 28
30-34 58 35
35-39 60 35
40-44 54 29
White, Non-hispanic 57 32
Black 48 22
Hispanic 56 22
<12 years 47 18
12 years 50 24
13-15 years 56 29
16+ years 59 37
Medicaid 50 21
Other 55 30
TOTAL 55 29

Table 6 shows the percent of women who know that folic acid prevents some birth defects. The overall percent, 36, is higher than the national percent of 13. Again, younger and minority women were less likely to know this. Women with more education and health insurance other than Medicaid were more likely to know that folic acid prevents some birth defects.

Table 6
Percentage of Women Who Know That Folic Acid Prevents Some Birth Defects BRFSS, 1997
Age Yes, Know Folic Acid
18-24 32
25-29 36
30-34 44
35-39 37
40-44 32
White, Non-Hispanic 42
Black 28
Hispanic 23
<12 years 17
12 years 27
13-15 years 35
16+ years 49
Medicaid 28
Other 37

Both these surveys indicate that we still need to educate women about the importance of folic acid and that there are specific groups of women who need to be especially targeted to receive the information.

Reference List

  1. MRC Vitamin Study Research Group: Prevention of neural tube defects: results of the medical research council vitamin study. The Lancet 1991;338:131-137.

  2. Cragan JD, Roberts HE, Edmonds LDMSPH, et al: Surveillance for anencephaly and spina bifida and the impact of prenatal diagnosis - United States, 1985-1994. Morbidity and Mortality Weekly Report 1995;SS-4:1-13.

  3. Centers for Disease Control: Recommendations for the use of folic acid to reduce the number of cases of spina bifida and other neural tube defects. Morbidity and Mortality Weekly Report 1992;vol. 41:

  4. Petrini JR, Damas K, et al.: Knowledge and use of folic acid-containing supplements among women of childbearing age - United States, 1995 & 1997. Morbidity and Mortality Weekly Report 1999;48:325-326.

  5. Adams MM, Shulman HBBC, Hogue C, Brogant D, and the PRAMS Working Group: The Pregnancy Risk Assessment Monitoring System: design, questionnaire, data collection and response rates. Pediatric and Perinatal Epidemiology 1991;333-346.