Context Studies have identified childhood sexual and physical abuse as a risk
factor for adolescent pregnancy but the relationship between exposure to childhood
abuse and unintended pregnancy in adulthood has, to our knowledge, not been
studied.
Objective To assess whether unintended pregnancy during adulthood is associated
with exposure to psychological, physical, or sexual abuse or household dysfunction
during childhood.
Design and Setting Analysis of data from the Adverse Childhood Experiences Study, a survey
mailed to members of a large health maintenance organization who visited a
clinic in San Diego, Calif, between August and November 1995 and January and
March 1996. The survey had a 63.4% response rate among the target population
for this study.
Participants A total of 1193 women aged 20 to 50 years whose first pregnancy occurred
at or after age 20 years.
Main Outcome Measure Risk of unintended first pregnancy by type of abuse (psychological,
physical, or sexual abuse; peer sexual assault) and type of household dysfunction
(physical abuse of mother by her partner, substance abuse by a household member,
mental illness of a household member).
Results More than 45% of the women reported that their first pregnancy was unintended,
and 65.8% reported exposure to 2 or more types of childhood abuse or household
dysfunction. After adjustment for confounders (marital status at first pregnancy
and age at first pregnancy), the strongest associations between childhood
experiences and unintended first pregnancy included frequent psychological
abuse (risk ratio [RR], 1.4; 95% confidence interval [CI], 1.2-1.6), frequent
physical abuse of the mother by her partner (RR, 1.4; 95% CI, 1.1-1.7), and
frequent physical abuse (RR, 1.5; 95% CI, 1.2-1.8). Women who experienced
4 or more types of abuse during their childhood were 1.5 times (95% CI, 1.2-1.8)
more likely to have an unintended first pregnancy during adulthood than women
who did not experience any abuse.
Conclusions This study indicates that there may be a dose-response association between
exposure to childhood abuse or household dysfunction and unintended first
pregnancy in adulthood. Additional research is needed to fully understand
the causal pathway of this association.
In 1994, 49% of US pregnancies were unintended (ie, unwanted or occurring
before the woman had intended to become pregnant).1
Approximately half of all unintended pregnancies result in abortion and those
that result in live births are associated with more maternal complications
and poorer infant outcomes than intended pregnancies.1,2
Several studies have identified exposure to sexual or physical abuse during
childhood as a risk factor for teenage pregnancies, most of which are unintended.3-6 Adolescents
who have been sexually abused are more likely to have a greater number of
sexual partners and to not use contraception, behaviors that increase their
risk of unintended pregnancy.3,4
To our knowledge, the relationship between exposure to childhood abuse
and household dysfunction and the risk of unintended pregnancy during the
adult reproductive years has not been studied. Most unintended pregnancies,
however, do occur in adult women. In 1994, women 20 years and older accounted
for 76% of all unintended pregnancies.1 Our
study explored whether a history of abuse or household dysfunction during
childhood was associated with an unintended first pregnancy during the adult
reproductive years.
We analyzed data from the Adverse Childhood Experiences (ACEs) Study.
A complete description of this study's method was published previously.7 Briefly, the ACEs study sample included San Diego,
Calif, enrollees in the Kaiser Permanente Medical Care Program who were encouraged
to receive a standardized medical examination. About 81% of enrollees 25 years
and older received such an examination in the Health Appraisal Clinic between
1992 and 1995. Those who were evaluated between August and November of 1995
or January and March of 1996 were mailed the ACEs study questionnaire, which
included questions about childhood psychological, physical, and sexual abuse,
and exposure to household dysfunction.
The sample included female respondents to the questionnaire who were
aged 20 to 50 years and who had had at least 1 pregnancy. Women whose reproductive
years occurred before the contraceptive pill was widely available (women ≥51
years) were excluded because contraceptive use is associated with pregnancy
planning. Women who had never been pregnant were also excluded because there
was no information on whether these women were infertile or successfully avoiding
unwanted pregnancies. After the questionnaire had been mailed a second time
to nonrespondents, the response rate was 63.4%. Respondents and nonrespondents
had answered questions about experiences of childhood sexual abuse and about
current health and psychosocial problems during their medical examinations.
There were no statistically significant differences between respondents and
nonrespondents in psychosocial or medical problems and respondents were no
more likely than nonrespondents to attribute their health and psychosocial
problems to sexual abuse (V. J. Edwards, PhD, R.F.A., D.F.N., et al, unpublished
data, 1998).
There were 1321 female respondents aged 20 to 50 years who had their
first pregnancy at or after age 20 years. We excluded 128 women (9.7%) because
of missing data for the pregnancy intendedness question; thus, 1193 women
made up the sample. There were no differences between women with missing data
and women with data for pregnancy intendedness, race/ethnicity, educational
attainment, age at first sexual intercourse, age at first pregnancy, age at
interview, and all of the childhood abuse or household dysfunction variables.
Women with missing data for pregnancy intendedness were more likely to have
unknown marital status at first pregnancy.
Women were coded as having had an unintended pregnancy if they answered
no to the question, "When your first pregnancy began, did you intend to get
pregnant at that time in your life?" Women were coded as having had an intended
pregnancy if they answered yes.
Respondents were considered to have been exposed to abuse or household
dysfunction if they responded positively to any of the questions included
in the definitions (Table 1).
We assessed 4 types of childhood abuse: psychological abuse (3 questions),
physical abuse (2 questions), sexual abuse (4 questions), and peer sexual
assault (1 question). We also assessed 3 types of household dysfunction: physical
abuse of the mother by her partner (4 questions), substance abuse by a household
member (2 questions), and mental illness of a household member (2 questions).
Questions from the conflict tactics scale8
were used to define psychological abuse, physical abuse, and physical abuse
of the mother by her partner. Sexual abuse questions were based on questions
developed by Wyatt.9 Questions on a household
member's abuse of alcohol or drugs were adapted from the 1988 National Health
Interview Survey.10
To assess a dose-response relationship between exposure to childhood
abuse or household dysfunction and an unintended first pregnancy during adulthood,
we examined separately the frequency of exposure to abuse and the additive
effect of experiencing more than 1 type of abuse or household dysfunction.
Frequency of the exposure was available for psychological abuse, physical
abuse, and physical abuse of the mother by her partner. We defined infrequent
exposure as events that occurred once, twice, or sometimes and frequent exposure
as events that occurred often or very often. To assess the effect of being
exposed to more than 1 type of abuse or household dysfunction, we also added
the number of types of exposure each woman reported. For this summary measure,
we included any psychological abuse (infrequent or frequent), physical abuse
(infrequent or frequent), physical abuse of the mother by her partner (infrequent
or frequent), sexual abuse, peer sexual assault, and household substance abuse
or mental illness.
Based on previous studies,1,11
we assessed 6 potential confounders: race/ethnicity, educational attainment,
marital status at first pregnancy, age at first sexual intercourse, age at
first pregnancy, and age at the time of the interview (20-39 and 40-50 years).
Women were considered to have been married during their first pregnancy if
the year of their first marriage was before or the same as the year in which
the pregnancy ended. Women with missing dates were coded as unknown marital
status. Age at interview was assessed as a potential confounder because of
the possibility of differences in the 2 age groups (20-39 and 40-50 years).
Missing observations were excluded from specific analyses as follows:
4 (0.3%) for race/ethnicity, 77 (6.5%) for age at first sexual intercourse
experience, 65 (5.4%) for age at first pregnancy, 20 (1.7%) for psychological
abuse, 20 (1.7%) for physical abuse, 87 (7.3%) for sexual abuse, 8 (<1.0%)
for peer sexual assault, 23 (1.9%) for physical abuse of the mother by her
partner, 1 (<1.0%) for substance abuse by a household member, and 10 (<1.0%)
for household member with a mental illness. Women with any missing observations
were statistically similar to women without any missing observations for all
types of childhood abuse or household dysfunction and for pregnancy intendedness.
Women with missing observations were more likely to have unknown marital status
at first pregnancy, to be less educated, younger, and of other race.
Separate logistic regression models assessed the association between
unintended pregnancy and each type of exposure to childhood abuse or household
dysfunction after adjustment of confounding variables. We used the change-in-estimate
strategy to evaluate whether a given potential risk factor was a confounder.12 The likelihood ratio test was used to assess first-order
interactions with educational attainment, marital status at first pregnancy,
age at first sexual intercourse, and age at first pregnancy for each type
of exposure to childhood abuse or household dysfunction. Because of multiple
tests for interactions, statistical significance was set at P = .01.
Since an adjusted odds ratio would have overestimated the risk ratio,
we computed an estimated adjusted risk ratio from logistic regression coefficients
by using the method described by Zhang and Yu.13
We calculated the attributable fraction, an estimate of the percentage of
unintended first pregnancies associated with experiencing 2 or more types
of abuse or household dysfunction during childhood.14
Almost 66% of women reported exposure to at least 2 types of abuse or
household dysfunction (Table 1).
The number of different types of abuse or household dysfunction ranged from
0 to 7; the mean number of types of exposure was 2.5. Psychological and physical
abuse were the most common. Almost 30% of the respondents reported a history
of sexual abuse and 28.5% had mothers who had been physically abused by their
partners.
Most respondents were white, had some college education or were college
graduates, and were married at the time of their first pregnancy (Table 2). About 70% of the women were 18
years or older when they first had sexual intercourse. Most respondents had
their first pregnancy when they were aged 20 to 24 years and were between
40 and 50 years of age at the interview.
More than 45% of the women reported that their first pregnancy was unintended
(Table 2). Percentages of unintended
first pregnancy were higher for women who reported frequent abuse or household
dysfunction during childhood than for women who reported infrequent abuse
or household dysfunction during childhood (Table 3). In addition, as the number of types of exposure to abuse
or household dysfunction during childhood increased, the percentage of women
with an unintended first pregnancy increased from 31.9% among women with no
exposures to 63.7% among women with 4 or more types of exposure.
Using the change-in-estimate strategy to assess for confounding, 2 variables
were identified as confounders: marital status and age at first pregnancy.
Most associations between unintended pregnancy and childhood abuse and household
dysfunction were statistically significant except for infrequent psychological
abuse, substance abuse by a household member, and mental illness of a household
member (Table 3). The strongest
associations with an unintended first pregnancy included frequent psychological
abuse (adjusted relative risk [RR], 1.4; 95% confidence interval [CI], 1.2-1.6),
frequent physical abuse of the mother by her partner (adjusted RR, 1.4; 95%
CI, 1.1-1.7), and frequent physical abuse (adjusted RR, 1.5; 95% CI, 1.2-1.8).
The RRs for unintended first pregnancy were higher for women who reported
frequent abuse or household dysfunction during childhood than for women who
reported infrequent abuse or household dysfunction during childhood. For example,
the adjusted RR was 1.2 (95% CI, 1.0-1.4) among women who reported infrequent
physical abuse and 1.5 (95% CI, 1.2-1.8) among women who reported frequent
physical abuse. Women who experienced 4 or more types of abuse during childhood
were 1.5 times (95% CI, 1.2-1.8) more likely to have an unintended first pregnancy
during adulthood than women who did not experience any abuse. The goodness-of-fit
test indicated that each of the 7 logistic models adequately explained the
variability in the data, suggesting that important variables were not omitted
from the models. No significant interactions were found with educational attainment,
marital status, age at first sexual intercourse, and age at first pregnancy.
The attributable fraction for having an unintended first pregnancy due
to experiencing 2 or more types of abuse or household dysfunction during childhood
was 20%. Therefore, 1 in 5 unintended first pregnancies was associated with
the woman's history of abuse and household dysfunction during childhood.
This study documented a dose-response association between exposure to
childhood abuse or household dysfunction and unintended first pregnancy during
adulthood. When adjusting for confounders, women who experienced frequent
physical abuse or were exposed to 4 or more types of abuse were 1.5 times
as likely to have an unintended first pregnancy as women who did not experience
abuse. Although the RRs were relatively modest, given the common occurrence
of the outcome (>45%), we found that 1 in 5 of the unintended pregnancies
was associated with childhood exposure to abuse. Our findings are consistent
with those of other studies in which associations between physical or sexual
abuse and risky sexual behaviors during adolescence were reported.3-6 Our study
suggests that the effects of childhood abuse continue past adolescence into
adulthood. Although other studies found associations between physical or sexual
abuse and unintended pregnancy, our study provides new evidence for an association
between unintended first pregnancy and other types of adverse childhood experiences,
including psychological abuse, peer sexual assault, and physical abuse of
the mother by her partner.
Additional research is needed to understand the casual pathway. The
abuse or household dysfunction may influence a woman's feelings of control
or power in sexual relationships and may lead to difficulty in negotiating
contraceptive use with a partner. A recent national study found that adult
women who did not use contraception but who did not want to become pregnant
were more likely to have had more than 1 partner over the course of a year;
additionally, those who were ineffective users of contraception were more
likely to be in unstable relationships or to have experienced sexual pressure
or coercion.15 Because we did not have information
on each woman's relationship including current abuse at the time of the first
pregnancy, number of sexual partners, or contraceptive use at the time of
the unintended pregnancy, we were unable to explore these intermediary variables.
However, the ACE Study found that 2 related lifetime variables—ever
having had a sexually transmitted disease and having had 50 or more sexual
partners—were associated with abuse and household dysfunction during
childhood among both men and women.7 The strength
of the association between unintended first pregnancy and childhood abuse
or household dysfunction diminished somewhat after adjustment for age and
marital status at first pregnancy. While we treated these variables as confounders
to present a conservative measure of association, these variables may be in
the casual pathway between abuse during childhood and subsequent unintended
pregnancy during adulthood.
To our knowledge, this is the first study to explore the association
in adult women between a history of child abuse and household dysfunction
and an unintended first pregnancy. A limitation of this study is that the
validity and reliability of our measures of abuse, household dysfunction,
and pregnancy intendedness are unknown. However, a strength is that our data
are consistent with data from other studies. For example, the prevalence of
childhood sexual abuse in our study (30%) is similar to that reported in a
national survey (27%).16 Also similar to findings
of a national survey, percentages of unintended pregnancy were higher for
black women, unmarried women, and younger women than for their counterparts.1,11 Another strength of this study is
the wide range of types of childhood abuse and household dysfunction explored.
Given the social stigma of abuse and the possible repression of memories,
percentages of abuse and household dysfunction may have been underreported.
Unintended pregnancies ending in abortion also are likely to have been underreported.17 In addition, the percentage of women with histories
of physical and sexual abuse is high among those attending abortion clinics.18,19 In a retrospective study such as
ours, there is always a possibility of recall bias. However, we have no information
as to whether women who have been abused are more or less likely to report
an unintended pregnancy. In the absence of a recall bias, the underreporting
of abuse and unintended pregnancy would underestimate the strength of the
relation between the childhood exposures and unintended pregnancy during adulthood.
The generalizability of our findings to other populations can be assessed
only if our findings are replicated in independent samples of women. We limited
our study sample to women for whom the contraceptive pill was generally available
during their reproductive years (women 50 years and younger at the time of
the study). We did analyze the data from women 51 years and older at the time
of the study and found similar results (data not shown). Given the strong
association between contraceptive use and pregnancy planning, however, our
findings may be most generalizable to cohorts of women aged 20 to 50 years
who had their first pregnancy during adulthood.
This study documented an association between exposure to abuse and household
dysfunction during childhood and a subsequent unintended first pregnancy during
adulthood. The vast majority of women in this study had experienced some type
of abuse or household dysfunction during their childhoods, and almost 1 in
5 unintended pregnancies was associated with those negative experiences. The
pathways through which childhood abuse and household dysfunction affect sexual
behavior in adulthood are complex and not fully understood. Nonetheless, our
findings suggest that medical providers need to be aware that a history of
abuse or household dysfunction is common among adult women and may be affecting
their patients' ability or motivation to prevent an unintended first pregnancy.
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