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To learn whether female cancer survivors are more likely to terminate a pregnancy by choice than other women, the occurrence of induced abortions was determined in a population-based cohort of 1688 childhood cancer survivors. Proportion ratios (PRs) were estimated from the ratio of the proportion of pregnancies that resulted in induced abortions among the survivors (or 16 700 randomly selected population control subjects) to the proportion among 2737 sisters of the survivors. The proportion of induced abortions among survivors (292 of 1479 [19.7%]) was marginally higher but not statistically significantly different from that among sisters (961 of 5092 [18.9%]; PR = 1.08, 95% confidence interval [CI] = 0.96 to 1.22) and similar to that of the population control subjects (5505 of 27 989 [19.7%]; PR = 1.07, 95% CI = 1.01 to 1.14). Survivors were not more likely than sisters and population control subjects to elect a second-trimester abortion because of physical and mental conditions or fetal abnormalities.
Studies have suggested that cancer survivors are concerned about the possible risks of having children.
The proportion of induced abortions among cancer survivors was compared with that among population control subjects and sisters of survivors, using sisters as the referent.
The proportion of induced abortions among cancer survivors was similar to that of population control subjects.
In this study, cancer survivors were not more likely to have induced abortions than population control subjects.
Associations with cancer therapies were not evaluated, so conclusions regarding specific cancer treatments could not be drawn. Data regarding the proportion of pregnancies desired and reasons why first-trimester abortions were induced were not available, so the authors could not directly assess how many cancer survivors wanted to have children or how many had early abortions because of risks related to having cancer.
From the Editors
Several studies have indicated that cancer survivors are very concerned about the possible health and social risks of having children (1–3). Recently, the Childhood Cancer Survivor Study (CCSS) (4) reported statistically significantly more induced abortions among US female childhood cancer survivors than among sibling control subjects. In the current population-based cohort study, we evaluated the rate of induced abortions in a similar patient group, after including indications for second-trimester abortions.
As previously described in greater detail (5), we identified from the Danish Cancer Registry 5508 women who were born between 1950 and 1984, in whom cancer was diagnosed before age 20 years between 1950 and 1996, and who were alive in 1968. The unique patient identification numbers were linked to the Central Population Register (CPR) to obtain data about vital status and first-degree relatives. The 1688 female cancer survivors who survived at least until 15 years of age formed the survivor cohort. The sister comparison group (n = 2737) consisted of sisters of the survivors who fulfilled similar inclusion criteria. Only survivors and their siblings born in 1950 or later were included because sibling identification before 1950 was incomplete. In addition, a population comparison group of 16 700 women was randomly selected in the CPR on the basis of birth month and year of survivors for a ratio of population control subjects to survivors of 10 to 1.
During 1977–2003, 34 560 pregnancies of female cancer survivors, their sisters, and population control subjects were identified, and pregnancy outcomes were determined. Live births and stillbirths were identified in the CPR (started in 1968) and in the Medical Birth Register (1973). Information on induced first- and second-trimester abortions was obtained from the Register of Induced Abortions (1977–1994) and from the National Hospital Register, thereafter (6). Since 1973, The Danish Abortion Act has permitted abortion on request during the first trimester for female residents aged 18 years and older (section one [§ 1] of the Act). For second-trimester abortions, permission is required from a special committee (§ 2–7.1).
The proportion of pregnancies (ending in live birth, stillbirth, or an abortion) among survivors that resulted in an induced abortion was compared with that among population control subjects and sisters as adjusted proportion ratios (PRs), with sisters as the referent. Proportion ratios were estimated by log-linear regression under the assumption that the outcome was binomially distributed and adjusted for age of the mother and calendar time (5). The generalized estimating equations method was used to accommodate correlation between pregnancy outcomes in the same woman, and 95% confidence intervals (CIs) were calculated using empirical variance estimates (7).
In 1977–2003, the proportions of pregnancies that resulted in an induced abortion were 19.7% among survivors (292 of 1479), 19.7% among population control subjects (5505 of 27 989), and 18.9% among sisters (961 of 5092). The proportion of induced abortions among survivors was marginally higher but not statistically significantly different from that of sisters (PR = 1.08, 95% CI = 0.96 to 1.22) and similar to that of the population control subjects (PR = 1.07, 95% CI = 1.01 to 1.14) (Table 1). Only survivors of bone tumors had statistically significantly more induced abortions than sisters (PR = 1.7, 95% CI = 1.2 to 2.3). Five of these nine women had at least one live birth.
Most (93%) induced abortions occurred during the first trimester in all three cohorts (§ 1, Table 2), and all groups had similar proportions of second-trimester terminations due to deterioration of physical or mental health (§ 2, § 3.1, § 3.4, and § 3.6 combined) (<2% of all induced abortions) or due to fetal abnormality (§ 3.3) (<1%).
Infertility is not the only issue in deciding whether to have children after cancer (1–3). Cancer survivors worry about whether their children would be healthy and whether they might pass on a genetic risk or predisposition for cancer. Reassurance is provided in several studies addressing reproductive hazards of mutagenic treatments (5,9–11), but this information may not be widely accessible to the survivors (2). Survivors also worry about being a future burden on their child because of their own physical health problems and the possibility of their cancer recurring later in life. It is therefore notable that cancer survivors did not have more induced abortions than the population control subjects. It is, however, not entirely clear why there should be a difference (if it is real and not just a chance finding) between the sisters and the population control subjects.
In the CCSS (4), 695 of 4029 (17%) pregnancies among survivors resulted in an induced abortion, that is, a proportion similar to that in the three Danish cohorts presented here, which ranged from 19% to 20%. However, US sibling control subjects reported fewer induced abortions (220 of 1903 [12%]), than Danish sisters (961 of 5092 [19%]). This difference among siblings in the two countries might be due to chance, to reporting bias if US siblings were less likely to admit to an elective abortion than their sisters who survived cancer, or to selection bias if the sisters who agreed to participate in the CCSS study were less likely to have had an induced abortion than those who refused to participate.
Missing an extremity, having prosthesis, or using crutches or a wheelchair subsequent to amputation might influence the choice to terminate a pregnancy and thereby explain the excess terminations reported in bone cancer survivors. Many survivors, however, also had live births. Chance due to multiple comparisons and small numbers is thus a possible explanation for this statistically significant association.
The study has several potential limitations, the most important of which is the small number of outcomes. In addition, associations with specific treatments were not evaluated. Psychosocial data, such as the proportion of pregnancies that are desired as well as indications for first-trimester abortions would have been valuable. Such data, however, could only be obtained by asking the women themselves, which was not feasible in this record-linkage study.
The study also had several strengths. These include the population-based approach with unbiased ascertainment of all childhood cancer survivors via the nationwide cancer register, unbiased identification of comparison groups, unbiased and complete ascertainment of induced abortions from health registers, and knowledge of indications for late terminations. Overall, the findings of the study suggest that female cancer survivors who are able to become pregnant believe and act as if they are healthy enough to be parents and are willing to carry through a pregnancy.
This work was supported in part by contracts and grants from Westlakes Research Institute (agreement no. 01/12/99 DC to J.D.B.), the National Cancer Institute (grant RO1 CA104666 to J.D.B.), and the Danish Cancer Society.
We thank data manager Andrea Bautz, Institute of Cancer Epidemiology, for preparing the data set for analysis. The sponsors had no role in the study planning and design, the collection and analysis of the data, the interpretation of the results, the preparation of the manuscript, or the decision to submit the manuscript for publication.