Antenatal screening for Down syndrome is a rapidly changing area of routine obstetric care. Until the introduction of maternal serum alpha-fetoprotein (MSAFP) as a screening test for Down syndrome in the 1980s, maternal age and history of a previously affected offspring were used to assess the risk for Down syndrome in pregnancy.1 In the mid 1980s, it was noted that patients in the second trimester with decreased MSAFP levels were at increased risk for fetal Down syndrome.2,3 As a result, noninvasive second-trimester Down syndrome screening for the general obstetric population became feasible, and in the 1990s, a multiple marker serum panel was established for this purpose.4 The “quad screen” (MSAFP, hCG, unconjugated estriol, and inhibin-A) detects approximately 75% of cases of Down syndrome with a 5% false-positive rate.5
Great efforts have been put forth to devise even more efficient screening protocols using first-trimester ultrasonography and serum analytes.1 Combined screening (nuchal translucency ultrasonography and first-trimester serum markers that include pregnancy-associated plasma protein-A [PAPP-A] and free β-hCG) detects 87% of cases of Down syndrome at 11 weeks of gestation and 82% of cases at 13 weeks of gestation, both with a 5% false-positive rate.6
Interest in improving screening for Down syndrome has not ended with first-trimester screening. New combinations of serum and ultrasound markers are being developed.1,7–9 Methods to combine first- and second-trimester screening protocols as well as second-trimester ultrasonography with the goal of offering patients choice while improving detection rates and decreasing false-positive rates are being explored.6,10–12
The purpose of this study was to assess the practice patterns, knowledge, and professional education of practicing obstetricians regarding screening for Down syndrome. Our hypothesis is that screening for Down syndrome is a rapidly changing aspect of routine obstetric care, and many practicing obstetricians may not be up-to-date on advances which may benefit patients. If areas of insufficient knowledge are identified, educational programs may be developed and implemented to better help practicing obstetricians and their patients.
MATERIALS AND METHODS
In August 2004, questionnaires were mailed to 1,105 American College of Obstetricians and Gynecologists (ACOG) Fellows and Junior Fellows in Practice. Of these subjects, 605 were members of the Collaborative Ambulatory Research Network, and 500 were a computer-generated random sample of ACOG members who had not received a survey from ACOG during the previous 2 years (non–Collaborative Ambulatory Research Network). Members of Collaborative Ambulatory Research Network are practicing obstetrician-gynecologists who responded to a Collaborative Ambulatory Research Network membership invitation letter that was included in a past survey mailing that had been sent to randomly selected ACOG members. Collaborative Ambulatory Research Network membership has no requirements beyond active ACOG Fellowship status, and members are mailed 4–5 short questionnaire surveys each year on various topics in women’s health care. Collaborative Ambulatory Research Network was established to increase response rates on survey studies and thus facilitate assessment of clinical practice patterns and aid the development of educational materials. Collaborative Ambulatory Research Network members represent each of the 10 ACOG Districts and typically have not differed from large random samples of practicing ACOG Fellows and Junior Fellows on our other survey instruments.13
The questionnaire was developed in consultation with medical specialists and was pilot tested on a sample of practicing obstetrician-gynecologists before final distribution. Institutional review board exemption was obtained from the Columbia University Medical Center. Two reminder mailings were sent to nonrespondents, and questionnaires returned by December 31, 2004, were included in the survey. This protocol has typically resulted in a total sample size of greater than 450, which is sufficient to detect differences between groups of less than 0.5 standard deviation with power of 80% and significance at the 0.05 level.14
The survey recorded demographic details of physicians and their patient population and assessed practices and knowledge regarding screening for Down syndrome. All practice and knowledge questions were of multiple-choice format. Management styles, didactic knowledge, and professional education pertaining to first- and second-trimester screening for Down syndrome, genetic counseling, and invasive prenatal diagnosis were assessed. A copy of the questionnaire is available on request.
The data were analyzed using a personal computer–based software package (SPSS 12.0, SPSS Inc., Chicago, IL). Descriptive statistics were computed for the measures used in the analyses, which are reported as mean ± standard error of the mean. Student t tests were used to compare group means of continuous variables. Differences on categorical measures were assessed using χ2. Group differences on ordinal measures were assessed using the Mann-Whitney U or Kruskall Wallis tests. Correlations including an ordinal measure used the Spearman’s ρ coefficient. All analyses were tested for significance using an alpha of 0.05.
A total of 670 questionnaires were returned. Data from 18 respondents were judged invalid (physician retired, returned to sender), resulting in a response rate of 60% (652/1,087). There were responding physicians from each of the United States except Maine, as well as from the District of Columbia, Puerto Rico, Canada, and overseas military installations. Respondents’ mean age (47.32 ± 0.39) and sex ratio (males = 55%) closely matched those of the larger population to whom the survey was sent (46.99 ± 0.32, males = 55%) and of ACOG Fellows and Junior Fellows as a whole (47.64, males = 58%).
The remaining analyses are limited to the 82% (532) of respondents who manage obstetric patients in their practice. Obstetrician demographics are shown in Table 1. Collaborative Ambulatory Research Network differed significantly from non–Collaborative Ambulatory Research Network on only 1 nondemographic item (a small increase in the proportion of physicians discussing carrier screening with all pregnant patients regardless of patient history). Therefore, data are collapsed across Collaborative Ambulatory Research Network and non–Collaborative Ambulatory Research Network subjects.
Obstetricians were asked about their use of first- and second-trimester screening tests (Table 2). When conducting first- or second-trimester serum screening, the majority of physicians (76%) base gestational age on ultrasound dating if there is a significant size and date discrepancy and the estimated date of delivery has been revised. Ultrasound dating alone was used by 22% of obstetricians, and 2% reported reliance on menstrual dating alone. Exclusive use of ultrasonography was associated with longer duration in practice (Mann-Whitney U 16,980.5, P = .001), for both males (P < .05) and females (P < .05).
More than three fourths (78%) of physicians reported routinely discussing aneuploidy screening with all pregnant patients. Of the 113 physicians who do not routinely discuss such screening with all pregnant patients, 92% said they discuss screening if the patient was of advanced maternal age. Eighty-five percent indicated they discuss screening if the patient had a significant family or medical history. Eighty percent indicated they discuss screening if an abnormal fetal ultrasound finding was diagnosed, and 74% indicated they discuss screening if the patient initiated the discussion. One percent of physicians said they do not routinely discuss screening for aneuploidy. Those who discussed aneuploidy screening with all patients were more likely to have been in practice a shorter duration (Mann-Whitney U 15,201, P < .001). Two thirds (67%) of physicians reported routinely discussing carrier screening for heritable genetic disorders with all pregnant patients. Of the remaining 170 physicians who do not discuss such screening with all patients, 88% said they discuss screening if the patient had a family history of heritable genetic disorders. Fifty-eight percent said they discuss screening if the patient’s reproductive partner had a heritable genetic disorder, and 53% said they discuss screening only if the patient initiated the discussion. Eight percent of respondents reported not routinely discussing screening for heritable genetic disorders with pregnant patients.
Obstetricians were asked several questions about invasive prenatal diagnostic testing (Table 3). Obstetricians were more likely to offer amniocentesis (88%) to patients who are at elevated risk for genetic abnormalities than chorionic villus sampling (CVS) (44%), and they were more likely to perform amniocentesis personally (37%) than CVS (2%). Of physicians who perform amniocentesis for multiple gestations, 66% reported using a multiple puncture technique, whereas 6% use a single-puncture technique, and 28% said it depended upon the situation. Seventy-eight percent use indigo carmine when performing amniocentesis on multiple gestations. The vast majority of respondents (98%) do not perform CVS. The 10 physicians who reported performing CVS use both the transabdominal and the transvaginal approaches.
Physicians were asked what number they quote their patients regarding risk of pregnancy loss after amniocentesis. Eighty-five percent quote a risk of 1 in 200 or greater, whereas 8% quote 1 in 100, and 5% do not quote a specific risk number. Almost one half (49%) of the respondents recommend amniocentesis at a gestational age of 15 weeks or more. Thirty-three percent suggest at 16 or more weeks, and 18% recommend amniocentesis before 15 weeks of gestation. Regarding quoted risk of pregnancy loss associated with CVS, 40% quote a risk of 1 in 100, 21% quote 1 in 200, 6% quote 1 in 50, and 31% do not quote a specific risk number. Most respondents (57%) said they recommend CVS at 10 or more weeks of gestation, including 9 of the 10 physicians who perform CVS. Twenty-eight percent recommend the procedure at 11 or more weeks of gestation and 15% suggest CVS at less than 10 weeks of gestation.
The majority of physicians (60%) refer patients to a genetic counselor for formal genetic counseling, whereas 34% reported that they refer to a genetic counselor and also provide counseling themselves. Only 4% (n = 21) of respondents provide counseling themselves exclusively (not limited to maternal–fetal medicine specialists), and 2% reported not having access to formal genetic counseling services. The vast majority of physicians (98%) offer prenatal screening and diagnosis to patients who would not consider pregnancy termination.
Physicians’ responses to 4 knowledge questions about screening for Down syndrome are shown in Table 4. There was a positive correlation between the number of Down syndrome cases managed in their career and the number of questions answered correctly (Spearman’s ρ .136, P < .002), but not between number of deliveries performed in 2003 and number of correct answers (P = .527). The 40 physicians who identified maternal–fetal medicine as their specialty were more likely to answer questions correctly than were non–maternal–fetal medicine specialists (Mann-Whitney U 6,192.5, P < .001). There were positive correlations between number of questions answered correctly and self-ratings of qualifications for general prenatal genetic counseling (Spearman’s ρ .170, P < .001), counseling a patient at elevated risk of fetal aneuploidy (Spearman’s ρ .261, P < .001), counseling a patient screen positive for aneuploidy (Spearman’s ρ .211, P < .001), and rating of residency training (Spearman’s ρ .158, P < .001) (below).
Physicians rated how well qualified they were to manage 3 types of counseling (Table 5). They were also asked to rate their residency training regarding prenatal screening and diagnosis of fetal aneuploidy. Although 55% indicated that their training was adequate to comprehensive, 28% said barely adequate, and 17% said inadequate to nonexistent. There was a significant negative correlation between years in practice and rating of residency training (Spearman’s ρ −.362, P < .001), such that those further removed from residency training were more likely to say that their training was inadequate. Physicians were asked to indicate what sources of information they use to stay informed about advances in genetic counseling and screening related to pregnancy. The majority (86%) indicated ACOG publications were an important source of information.
Genetic counseling and screening for Down syndrome are important aspects of routine obstetric practice. Screening programs allow patients to obtain a risk assessment to determine whether invasive prenatal diagnosis should be considered. This area of obstetrics is rapidly changing due to advances in genetics as well as the completion of studies evaluating the efficacy of population-based screening for Down syndrome using ultrasonography and first- and second-trimester serum markers.6,10 Although this survey of contemporary practicing obstetricians suggests that the majority of practitioners manage patients according to ACOG educational materials with regard to genetic counseling and screening for aneuploidy,15–17 areas of deficiency have been identified that require improvement before universal first-trimester screening for aneuploidy can be employed.
First-trimester screening for Down syndrome offers advantages over second-trimester screening. Patients obtain a risk assessment early in pregnancy and may obtain definitive diagnosis by first-trimester CVS if they are screen positive. If the patient desires voluntary termination of pregnancy, the procedure can be performed early in gestation, which is associated with decreased maternal morbidity and increased privacy.15 Although second-trimester amniocentesis is an option for patients who are screen positive on first-trimester screening, waiting until the second trimester for definitive diagnosis may be associated with anxiety.1 It has been proposed that first-trimester screening should only be offered if patients have access to early diagnosis by CVS.15 This survey indicates that few practitioners perform CVS, and this finding is consistent with other recent studies. In a 2004 survey study of ACOG members, only 3.6% of respondents performed CVS.18 A 2001 survey of United States maternal–fetal medicine specialists pertaining to Down syndrome screening also suggested that there may be a paucity of physicians who are skilled at this diagnostic procedure.19 In the study by Egan et al19 only 6% of maternal–fetal medicine specialists reported performing CVS. In a 2001 survey of maternal–fetal medicine fellows in training, although 82% indicated that physicians at their teaching institution performed CVS, only 53% of responding fellows reported having access to CVS training.20 This small number of practitioners skilled at the procedure and small number of practitioners becoming trained in the procedure may make the widespread implementation of first-trimester screening challenging. If first-trimester screening is offered universally, a significant increase in demand for CVS will likely occur, and large segments of the population may not have access to the procedure.21 Educational programs to train specialists in this invasive diagnostic technique are needed. Regional referral centers for CVS may be an option.
Even though few practitioners perform CVS, many patients must have access to this procedure because their physicians are referring them to qualified specialists, as suggested by our study. Although 2% of respondents perform CVS, 51% indicated that they offer CVS to their patients, and 49% responded that they did not routinely offer it. These numbers suggest that 51% of practicing obstetricians can obtain CVS for their patients despite the fact that they do not perform the procedure themselves. Regardless, these numbers suggest that before first-trimester screening can be offered universally, efforts are needed to facilitate access to CVS.
Forty-five percent of respondents felt that their training regarding prenatal diagnosis was barely adequate or inadequate to nonexistent. Consistent with their rating of their training, practitioners’ knowledge regarding screening for aneuploidy was less than anticipated. This finding was in accord with 2 smaller studies of prenatal care practitioners and Down syndrome screening.22,23 In our study, fewer than half (46%) responded correctly that a 40-year-old woman’s term risk of having a Down syndrome affected child is approximately 1 in 100.24,25 A minority (23%) indicated that a first-trimester cystic hygroma is associated with a 50% risk for fetal aneuploidy.26 Thirty percent of respondents answered that a normal genetic ultrasonography can reduce a patient’s a priori risk for having a pregnancy affected by Down syndrome by 51–75%.16 Fewer than one half (41%) correctly answered which serum marker abnormalities (decreased MSAFP, decreased estriol, increased hCG, and increased inhibin-A) were associated with an increased risk for Down syndrome.27 It was also interesting to note that the majority of respondents (76%) base gestational age for screening for aneuploidy on ultrasonography only if there is a significant size and date discrepancy. Screening for aneuploidy in both the first and second trimesters yields more precise risk estimates when gestational age is assigned by ultrasonography alone, irrespective of menstrual dating.5
The findings of this questionnaire study are positive—the majority of practicing obstetricians manage patients according to ACOG educational materials with regard to genetic counseling and screening for aneuploidy. The majority of obstetricians (78%) counsel all patients about risks for fetal aneuploidy, and 67% provide counseling for heritable genetic abnormalities. Over one half (55%) offer first-trimester screening for Down syndrome, and the majority (99%) offer second-trimester Down syndrome screening. Likewise, areas of deficiency have been pinpointed (scarcity of practitioners performing CVS and physician assessment that their training regarding prenatal diagnosis is not sufficient) that should be amenable to improvement.
Our study has limitations that should be acknowledged. The response rate was 60%, and not all respondents were included in the analysis because not all were practicing obstetrics at the time of this survey. Thus our findings are based on the responses of 532 practicing obstetricians. Although our study may be subject to nonresponse bias, we believe that our findings are reliable. The typical response rate in these survey studies is approximately 35% to 60%, and our response rate was at the high end of expected participation. Previous similar studies have demonstrated that reliable results can be obtained, and the minimal number of responses needed to ensure significant effect sizes is approximately 100 respondents.28 In addition, the responses are derived from geographically diverse locations and from physicians from different practice types, reflecting the influence of physician location and practice type on management patterns. It is possible that physicians who were more interested in or knowledgeable about the topic of the survey were more likely to respond. In an attempt to control for this, a subset of our subject pool is comprised of Collaborative Ambulatory Research Network members, who are asked to respond to several questionnaires a year, covering a wide variety of topics. It is unlikely that Down syndrome screening is a topic of greater interest to this control group than to the group of randomly selected ACOG members. Collaborative Ambulatory Research Network members had a 72% response rate and made up 66% of respondents to this questionnaire. They differed significantly from non–Collaborative Ambulatory Research Network subjects on only 1 nondemographic response, and the age and sex ratio of respondents as a whole closely matched the characteristics of the larger population to whom the survey was sent, all of which suggests that response bias was minimized.
In summary, this survey of contemporary practicing ACOG Fellows and Junior Fellows suggests that the majority of obstetricians manage patients with regard to screening for aneuploidy and genetic testing according to current ACOG educational guidelines.14–16 It is important to note that many practitioners do not feel comfortable with their level of training on these issues, and this lack of comfort was reflected in the fact that they answered fewer than 2 of the 4 knowledge questions pertaining to screening for aneuploidy correctly. In addition, very few practitioners perform CVS. The majority of contemporary obstetricians (86%) indicated that they rely on ACOG educational materials to remain up to date regarding screening for aneuploidy and genetic testing. Educational programs designed by ACOG may be helpful to better educate practicing obstetricians about this rapidly changing aspect of prenatal care so that patients can benefit from the most up-to-date counseling, screening protocols, and prenatal diagnostic techniques. Until these deficiencies are addressed, universal implementation of first-trimester screening for fetal aneuploidy may not be feasible.
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