Abortion for Fetal Anomalies: Trends in Gestational Age
By Rebecca H. Allen, MD, MPH
Associate Professor, Department of Obstetrics and Gynecology, Warren Alpert Medical School of Brown University, Women and Infants Hospital, Providence, RI
Dr. Allen reports she is a Nexplanon trainer for Merck, and has served as a consultant for Bayer and Pharmanest.
SYNOPSIS: In this retrospective cohort study, the median gestational age at the time of abortion for fetal aneuploidy decreased from 19 weeks in 2004 to 14 weeks in 2014. However, the gestational age at the time of abortion for fetal structural abnormalities remained at ≥ 20 weeks over the study period.
SOURCE: Davis AR, Horvath SK, Castano PM. Trends in gestational age at time of surgical abortion for fetal aneuploidy and structural abnormalities. Am J Obstet Gynecol 2017;216:278.e.1-278.e5. doi: 10.1016/j.ajog.2016.10.031. [Epub ahead of print].
This is a retrospective cohort study conducted from January 2004 to December 2014 at a single institution in New York City evaluating abortions up to 23 weeks and 6 days. At this institution, surgical abortion accounts for more than 99% of all pregnancy terminations. The authors included all abortions with a confirmed diagnosis of fetal aneuploidy or structural abnormalities in prenatal records. Fetal aneuploidy diagnosis required diagnostic testing (e.g., chorionic villous sampling or amniocentesis). Fetal structural abnormalities required imaging studies (ultrasound, MRI, or fetal echocardiography) confirming a fetal organ system anomaly with normal or unknown testing for aneuploidy. Cases for maternal or other fetal indications were excluded (e.g., demise, infection, cystic fibrosis, fragile X, etc.). Medical records for each case were reviewed. Medicaid covers abortion in New York; therefore, most women in the state have access to abortion.
The authors reviewed 3,853 cases and excluded 2,875 cases (2,801 for maternal indications, 73 for ineligible fetal indications, and one with incomplete information). A total of 978 cases were included: 392 (40%) with aneuploidy and 586 (60%) with structural abnormalities. Women who underwent abortion for fetal aneuploidy were older than women who had fetal structural abnormalities (37 years vs. 32 years; P < .001). The median gestational age for abortion associated with aneuploidy decreased from 19 weeks in 2004 to 14 weeks in 2014 (P < .001). A similar trend was found even for those cases of aneuploidy that had associated structural abnormalities. In contrast, the median gestational age for abortion for fetal structural abnormalities remained the same over the study period at 20.5 weeks in 2004 and 21.0 weeks in 2014 (P = .10). More women with fetal aneuploidy were able to undergo suction dilation and curettage instead of dilation and evacuation in 2014 (31%) compared to 2004 (0%).
COMMENTARY
This study is interesting because it documents the effect that newer technologies for diagnosing fetal aneuploidy are having on related procedures. Approximately 3% of pregnancies in the United States are found to have fetal anomalies.1 With the advent of first-trimester screening for aneuploidy (11-13 weeks) and cell-free DNA testing (10 weeks), more women are able to find out if their pregnancies might be affected earlier in gestation. Provided that chorionic villous sampling, which can be performed at 10 to 14 weeks’ gestation, is available, the patient then can obtain diagnostic confirmation of the aneuploidy. In this study, the distribution of chromosome abnormalities was trisomy 21 (52%), trisomy 18 (14%), trisomy 13 (7%), Turner syndrome (6%), Klinefelter syndrome (4%), mosaic (9%), and other (7%).
In contrast, fetal structural anomalies of the neurologic, cardiac, musculoskeletal, genitourinary, or other systems typically are not diagnosed until the second trimester ultrasound performed between 18 and 22 weeks. The diagnosis of these anomalies has not changed over time as much as diagnosis of fetal aneuploidy. Personally, I have seen an increase in first-trimester nuchal translucency ultrasounds detecting early neurologic defects (e.g., anencephaly). The use of first-trimester ultrasound to screen for congenital anomalies is being investigated.2 However, according to this study, the number detected has not influenced the overall trend that structural abnormalities still are diagnosed in the late second trimester. In addition, early ultrasound at 11 to 14 weeks never will be able to detect certain abnormalities that develop later. One meta-analysis showed that the ability of early ultrasound to detect structural abnormalities depended on the type (see Table 1).3
Table 1: Detection Rate of Fetal Malformations in the First Trimester |
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100% detection rate
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50-99% detection rate
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1-49% detection rate
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0% detection rate
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Some women diagnosed with fetal anomalies will opt for abortion if available.4 The advantage of early diagnosis if the woman desires pregnancy termination is increased safety with a less complicated procedure. As this study showed, more women were able to undergo suction dilation and curettage procedures rather than dilation and evacuation. Of course, in this study, abortion was covered by insurance and chorionic villous sampling was easily available. This is not the case in all areas of the country. The mortality of abortion increases with gestational age from 0.3 per 100,000 cases at ≤ 8 weeks compared to 6.7 per 100,000 cases at ≥ 18 weeks.5 Yet, this is still lower than mortality with childbirth overall.6 In addition, first-trimester and early second-trimester abortions are more accessible in most regions compared to late second-trimester abortions in terms of providers and facilities willing to perform the procedure. According to national surveys, 72% of providers offered abortions at 12 weeks, 34% at 20 weeks, and 16% at 24 weeks.7 Furthermore, states that have passed bans on abortion at > 20 weeks post-fertilization will affect women with structural abnormalities compared to aneuploidy disproportionately. According to the Guttmacher Institute, 16 states ban abortion at about 20 weeks post-fertilization or its equivalent of 22 weeks after the woman’s last menstrual period on the spurious grounds that the fetus can feel pain at that point in gestation. This greatly affects the choices that women have when confronted with the diagnosis of a fetal anomaly.
REFERENCES
- Centers for Disease Control and Prevention. Birth Defects. Available at: https://www.cdc.gov/ncbddd/birthdefects/data.html. Accessed March 21, 2017.
- Timor-Tritsch IE, Fuchs KM, Monteagudo A, D’alton ME. Performing a fetal anatomy scan at the time of first-trimester screening. Obstet Gynecol 2009;113(2 Pt 1):402-407.
- Rossi AC, Prefumo F. Accuracy of ultrasonography at 11-14 weeks of gestation for detection of fetal structural anomalies: A systematic review. Obstet Gynecol 2013;122:1160-1167.
- Shaffer BL, Caughey AB, Norton ME. Variation in the decision to terminate pregnancy in the setting of fetal aneuploidy. Prenat Diagn 2006;26:667-671.
- Zane S, Creanga AA, Berg CJ, et al. Abortion-related mortality in the United States: 1998-2010. Obstet Gynecol 2015;126:258-265.
- Raymond EG, Grimes DA. The comparative safety of legal induced abortion and childbirth in the United States. Obstet Gynecol 2012;119(2 Pt 1):215-219.
- Jerman J, Jones RK. Secondary measures of access to abortion services in the United States, 2011 and 2012: Gestational age limits, cost, and harassment. Women’s Health Issues 2014;24:e419-e424.
In this retrospective cohort study, the median gestational age at the time of abortion for fetal aneuploidy decreased from 19 weeks in 2004 to 14 weeks in 2014. However, the gestational age at the time of abortion for fetal structural abnormalities remained at ≥ 20 weeks over the study period.
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