Materials and Methods
Participants
Participants were 302 women pooled from 2 prospective perinatal studies of maternal mood and behavior and fetal and infant development. Participants were excluded from participating in the larger studies if their pregnancies were complicated by multiple gestations or maternal age younger than 18 or older than 40 years.
The primary aim of one study was to examine the effects of maternal smoking on fetal and infant development (grant R01 DA019558) and thus oversampled for maternal smoking during pregnancy. The aim of the second study was to examine effects of maternal depression on fetal and infant development (grant R01 MH079153) and thus oversampled for depression during and prior to the current pregnancy. Maternal smoking and depression were examined as predictors of PTB in subsequent models. These studies were approved by Women and Infants and Lifespan Hospitals’ institutional review boards. All women provided written consent prior to their participation. Study activities were conducted in the greater Providence, RI, region.
Procedure
As part of the larger studies, women were interviewed twice during the second and third trimesters of pregnancy (at approximately 27 [SD, 3.5] and 35 [SD, 1] weeks’ gestation). At the first interview, women reported adverse childhood experiences, socioeconomic characteristics, health and pregnancy history, prepregnancy height and weight, cigarette smoking and alcohol use, symptoms of depression and anxiety, perceived stress, and sleep quality. At the second interview, women were again interviewed about substance use, symptoms of depression and anxiety, perceived stress, and sleep quality.
Socioeconomic status was assessed by maternal education (1, less than seventh grade, to 7, graduate training with degree) and annual household income (approximately $10,000 increments from 1, <$5000, to 8, $100,000 or more). Participants reported their prepregnancy weight and height to compute their body mass index. Maternal medical conditions were assessed through medical chart review and maternal report and were summed for analyses.
Measures
Preterm birth
Gestational age at birth was defined as the number of days between the last menstrual period (collected by maternal self-report) or ultrasound (confirmed by medical chart review) and date of delivery. If gestational age as measured by ultrasound after 14 weeks’ gestation differed from the last menstrual period by ± 10 days, gestational age at birth was computed according to ultrasound calculations. Births were then categorized into those occurring prior to 37 weeks’ gestation to indicate PTB status. One preterm birth resulted in fetal death.
Maternal history of adoption/foster care
At the first study session, participants were asked 2 questions to determine maternal history of adoption (“Were you adopted?” [yes/no]) or foster care placement (“Were you ever in foster care or an institution because your parents were unable to take care of you?” [yes/no]). Participants were considered to have a childhood placement history if they were ever adopted and/or in foster care prior to age 18 years.
Maternal history of childhood sexual and physical abuse
This was determined from items from the Adverse Childhood Experiences Scale. Specifically, participants were asked how often, before the age of 18 years, they experienced child sexual abuse (4 items; eg, “How often did an adult person at least 5 years older than you touch or fondle your body in a sexual way?”) or physical abuse (4 items; eg, “How often did a parent, stepparent, or adult living in your home push, grab, slap, or throw something at you?”). Response options ranged from 0 (never) to 4 (very often). We then created dichotomous childhood sexual abuse and childhood physical abuse variables based on whether participants endorsed a score of 1 or higher (eg, “once or twice”) on relevant maltreatment items.
Psychosocial depression, anxiety, and stress
Symptoms of depression in the previous week was assessed using the Quick Inventory of Depressive Symptomatology. The Quick Inventory of Depressive Symptomatology scores range from 0 to 27; scores above 21 indicate severe depressive symptoms. Symptoms of anxiety over the past week were assessed by the Hamilton Anxiety Rating Scale administered at each study session. The Hamilton Anxiety Rating Scale scores range from 0 to 56; scores above 25 indicate moderate to severe anxiety. Perceived stress over the last month was assessed at each study session using the Perceived Stress Scale (10 items), a measure of daily hassles, a low perceived control over challenges, and a low perceived ability to cope with challenges over the previous month. Perceived stress scores range from 0 to 40, with higher scores indicating greater stress. Summary depression, anxiety, and stress scores were computed by averaging the scores for each measure across study sessions.
Health behaviors
Participants were interviewed regarding the number of cigarettes smoked and alcoholic drinks consumed throughout pregnancy using the Timeline Follow Back Interview. The total number of cigarettes and drinks in pregnancy were examined as continuous substance exposure variables. In addition, we included smoking status (smoker vs nonsmoker) by classifying women as smokers if they reported smoking more than 40 cigarettes in pregnancy. Sleep quality over the previous month was assessed via the Pittsburgh Sleep Quality Index. Scores on the Pittsburgh Sleep Quality Index range from 0 to 21; scores greater than 5 indicate poor sleep quality. The sum score of global sleep quality over pregnancy, averaged across the 2 study sessions, was examined in analyses.
Data analysis
All statistical analyses were performed using SPSS (version 20) software (SPSS Inc, Chicago, IL). The primary outcome of interest was PTB, binary variable (1, preterm). As a preliminary step, we examined associations among predictor variables using a regression analysis to rule out multicolinearity. All variance inflation factor scores were less than 3, indicating that multicolinearity was not evident in these analyses. Given the binary nature of our outcome variable, a stepwise multiple logistic regression analysis was performed to assess the association between maternal placement history and PTB (step 1) and the association between maternal placement history and PTB, adjusting for child maltreatment history, psychosocial distress, negative health behaviors in pregnancy, and maternal demographic and medical conditions in pregnancy (step 2).
Results
Sample characteristics
Maternal and infant characteristics are presented in Table 1 . Thirty-nine women in the sample (13%) reported a history of out-of-home placement in childhood. Twenty-six women in the sample (9%) delivered preterm, slightly lower than PTB rates in the United States (12%), which was consistent with aims of the larger studies to select samples of pregnant women at low risk for adverse neonatal outcomes. Twenty-four percent of the women experienced any infection and/or were prescribed antibiotics during pregnancy, and 6% of the sample experienced preterm labor.
| Characteristic | Mean or % | SD |
|---|---|---|
| Maternal | ||
| Age, y | 26 | 5 |
| Gravida, n | 3 | 2 |
| Planned pregnant, % yes | 41% | |
| Adopted or in foster care | 13% | |
| Childhood physical abuse, % yes | 41% | |
| Childhood sexual abuse, % yes | 23% | |
| Race, % non-Hispanic white | 50% | |
| Annual income, % <$10,000 | 11% | |
| Marital status, % married | 36% | |
| Cigarette smoking, % a | 30% | |
| Infant | ||
| PTB, <37 wks GA | 9% | |
| PTL, <37 wks GA | 6% | |
| Gestational age at birth, wks | 39 | 2 |
| Birthweight percentile | 48 | 25 |
| Apgar score at 5 min | 9 | .7 |
a Cigarette smoking was defined as smoking more than 40 cigarettes in pregnancy.
Association between childhood placement history and preterm birth
Multiple logistic regression analysis revealed that, prior to adjusting for maternal characteristics, women with placement histories were significantly more likely to deliver preterm compared with women without childhood placement histories (β = 1.34, SE, 0.51, P = .008, odds ratio [OR], 3.82; 95% confidence interval [CI], 1.30–8.92). In other words, 18% of the women with histories of childhood placement delivered preterm vs 6% of women without histories of childhood placement ( Figure ). The odds of delivering preterm were approximately 4 times greater among women with a history of out-of-home placement compared with women who were never placed out of the home during childhood.
Association between placement history and PTB adjusting for maternal characteristics
Next, using multiple logistic regression analysis, we explored whether the association between maternal placement history and PTB was significantly diminished after adjusting for maternal demographic characteristics, history of child maltreatment, psychosocial distress in pregnancy, or health behaviors. Results are presented in Table 2 . The association between placement history and PTB remained significant (β = 1.44, SE, .66, P = .02, OR, 4.22; 95% CI, 1.17–15.29), indicating that the association between placement history and PTB was not significantly accounted for by maternal characteristics or experiences in the perinatal period.
| Variable | β | SE β | OR | 95% CI for OR | P value |
|---|---|---|---|---|---|
| Childhood placement history (yes/no) | 1.44 | 0.66 | 4.22 | 1.17–15.29 | .02 |
| Childhood physical abuse (yes/no) | 0.02 | 0.07 | 1.02 | 0.89–1.16 | .74 |
| Childhood sexual abuse (yes/no) | 0.03 | 0.08 | 1.03 | 0.88–1.19 | .73 |
| Body mass index | –0.04 | 0.04 | 0.96 | 0.88–1.04 | .29 |
| Smoking status (yes/no) | 0.44 | 0.34 | 1.55 | 0.23–1.52 | .20 |
| Number of cigarettes in pregnancy | 0.00 | 0.00 | 1.00 | 0.99–1.00 | .77 |
| Number of alcoholic drinks in pregnancy | –0.02 | 0.02 | 0.98 | 0.94–1.03 | .41 |
| Sleep quality (PSQI) | –0.11 | 0.10 | 0.90 | 0.27–0.89 | .27 |
| QIDS score | –0.06 | 0.06 | 0.94 | 0.85–1.05 | .29 |
| Anxiety symptoms (HAM-A) | –0.009 | 0.07 | 0.99 | 0.86–1.14 | .90 |
| Perceived stress (PSS) | 0.25 | 1.04 | 1.26 | 0.16–10.12 | .81 |
| Maternal age | 0.09 | 0.06 | 1.10 | 0.99–1.23 | .10 |
| Gravida | –0.07 | 0.17 | 0.93 | 0.67–1.29 | .68 |
| Marital status | 0.04 | 0.12 | 1.04 | 0.83–1.30 | .75 |
| Family income | –0.03 | 0.14 | 0.97 | 0.74–1.28 | .82 |
| Maternal education | 0.04 | 0.27 | 1.04 | 0.61–1.77 | .88 |
| Medical conditions in pregnancy (yes/no) | 0.40 | 0.47 | 1.49 | 0.60–3.73 | .39 |
| Maternal race (white vs non-white) | 1.09 | 0.56 | 2.98 | 1.0–8.92 | .05 |
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