Interactional model for the association among maternal alcohol use, mother-infant interaction, and infant cognitive development

INFANT

BEHAVIOR

AND

DEVELOPMENT

16,

177-192

(1993)

Interactional Model for the Association Among Maternal Alcohol Use, Mother-Infant Interaction, and Infant Cognitive Development MARY

J. O’CONNOR, AND CONNIE

University

of California

MARIAN KASARI

SIGMAN,

at Los Angeles

The association among maternal alcohol consumption, mother-infant interaction, ond infant cognitive development wos exomined in this experiment. Structural equation modeling was used to test o model in which infant cognitive development, as measured by the Bayley Mental Scale, wos ossumed to be influenced by the infant’s affect and the mother’s ability to interact with the infant. It was hypothesized thot infants of mothers who drank more heavily prenatally would hove increased negative affect in interaction. The mothers of these infonts were predicted to be less stimulating ond elaborative in interaction. Infants experiencing less optimal interactions with their mothers were posited to exhibit lower cognitive performance. A direct poth between moternal prenatal alcohol use and infant outcome was also hypothesized. Results were consistent with the model suggesting that the mother’s alcohol use is directly associated with infant mental development and has teratogenic effects on infant affect which, in turn, relates to the mother-infont relationship and to infant cognitive perfarmance. Postnatal alcohol consumption was found to relate directly to infant cognition and not to infont affect or material interaction characteristics,

maternal

alcohol

use

mother-infont

interaction

infant

cognition

Considerable literature exists demonstrating the relation between maternal alcohol use and child cognitive and behavioral development. Heavy alcohol use during pregnancy has been documented as a causal agent in cognitive delay with milder effects associated with moderate or social drinking (Jones & Smith, 1973; O’Connor, Brill, & Sigman, 1986; Streissguth, Barr, & Martin, 1983; Streissguth, Landesman-Dwyer. Martin, & Smith, 1980). Behavioral attributes ascribed to infants and young children with fetal alcohol syndrome and fetal alcohol effects include state lability, irritability, poor attention, We

would

like

to

thank

Nancy

Wainwright.

Peter

Bentler,

assistance in manuscript preparation and statistical consultation. and children who participated in this research. Correspondence and requests for reprints should be sent 243C. Neuropsychiatric Institute, 760 Westwood Plaza. Los

and Special to Mary Angeles,

Gwen

Gordon

thanks J. O’Connor, CA 90024.

for

to the

their

mothers

Room

4S-

177

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O’CONNOR,

SIGMAN,

AND

KASARI

temper tantrums, distractibility, and impulsiveness (see Streissguth, 1986, for summary). Although most investigators have acknowledged that the socioemotional environment of the child is important for mediating prenatal alcohol effects, maternal and child characteristics often have not been measured or have been treated as covariates or confounding influences in highly controlled studies of the effects of maternal alcohol consumption on behavioral teratology. This approach is logical when one is trying to examine the “pure” effects associated with maternal alcohol consumption; however, questions remain concerning the complex interaction among alcohol consumption, the mother-infant dyadic relationship, and infant cognitive development. The importance of studying the mother-infant interaction is revealed in studies in which investigators have demonstrated that infant attributes of irritability, responsiveness, arousal, state regulation, and attention relate to maternal behavior toward the infant (Barnard, Bee, & Hammond, 1984; Boukydis & Burgess, 1982; Crockenberg, 1981; Goldberg, Brachfield, & DiVitto, 1980; Heinicke, Diskin, Ramsey-Klee, & Oates, 1986; Sigman, 1983). Similarly, the behavior of the mother toward the infant influences infant growth and development (Bakeman & Brown, 1980; Olson, Bates, & Bayles, 1984; Pianta, Sroufe, & Egeland, 1989; Sameroff & Chandler, 197.5). In this experiment, hypotheses were formulated to explain these complex interactional associations. Data were subjected to path analysis using the EQS program for structural equation modeling (Bentler, 1985). The statistical theory (Bentler, 1983a, 1983b; Bentler & Dijkstra, 1985; Browne, 1982, 1984; Shapiro, 1983) allows for the estimation of parameters and testing of models using traditional multivariate normal theory and the use of the more general elliptical and arbitrary distribution theories, based on a unified generalized least squares (GLS) or minimum chi-square approach. Specifically, the EQS technique allows a series of hypothesized regression equations to be solved simultaneously, generating an estimated covariance matrix that is used to test hypothesized models. This estimated matrix is then compared with the actual sample covariance matrix by means of a chi-square statistic. A nonsignificant chi square is consistent with an inference that the proposed theoretical model predicts relations between empirical variables accurately. The chi square will be significant if the model does not predict relations accurately. Variables for analysis were selected based upon theoretical and empirical considerations. Research has shown that maternal alcohol consumption is associated with infant irritability (Streissguth et al., 1983). Furthermore, infants with difficult temperaments have been shown to have disturbances in the mother-infant relationship (Campbell, 1979; Milliones, 1978; Pianta et al., 1989). These disturbances often are related to negative child outcome. Guided by the literature, a direct path was hypothesized between alcohol consumption and infant cognitive development, reported for three time peri-

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ods: prior to pregnancy recognition, during pregnancy, and postpregnancy. Furthermore, we proposed that mothers reporting high levels of alcohol consumption would have infants who displayed more negative affect in interaction with their mothers. The mothers of these infants would demonstrate less optimal interaction with their infants, which would be associated with lower cognitive performance. Additional paths were hypothesized to exist between the mother’s postnatal alcohol consumption, her interaction, infant affect, and cognition. These paths were added in order to investigate the effects of the mother’s drinking behavior following the infant’s birth. METHOD Subjects

Sample subjects were 44 firstborn infants (23 males, 21 females) whose mothers were 30 years of age or older. All mothers had been screened at the UCLA amniocentesis clinic because of advanced age. Older first-time mothers were chosen for study because they are at higher risk for producing offspring with fetal alcohol syndrome (Streissguth, 1978) and because these women represent a growing percentage of mothers who are having children for the first time. One month prior to the infant’s first birthday, a demographic questionnaire was mailed to the mother with a letter requesting her participation. Return rate was 75%. Subjects were enrolled in the experiment in chronological order based upon infant birth date. Fifty mothers and infants participated in the study but 6 were eliminated. Two were eliminated because English was not the primary language in the home, 1 because the father had received radiation therapy prior to conception, 1 because the child was second-born, and 2 because of experimenter error. The sample mothers represented a highly select group of preponderantly white (91%), educated (70% had achieved college graduate or postgraduate education), middle-class (lOO%), married (98%) women with an average age of 36.91 years (SD = 2.32). The average IQ of women in the sample was 118.93 (SD = 5.64) as measured by the Shipley Institute of Living Scale, which provides a quick and valid measure of overall intellectual functioning (Boyle, 1967). This highly select sample was recruited in order to reduce confounds associated with infant mental development. It was postulated that if effects were found in this relatively low-risk, middle-class population, they would be quite meaningful. Infants in the sample were all full-term with a mean birthweight of 3,553 gms (SD = 547.17). Procedure

Alcohol, Caffeine, Smoking, and Other Drug Use. When their infants were 1 year of age, mothers were asked to fill out a self-report questionnaire

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TABLE Alcohol Alcohol Averoge

Scores

Descriptive

AND

1 Statistics

Abbreviotion

ounces

of absolute

Prior to pregnancy During pregnancy Postpregnoncy Average drinks/occasion Prior to pregnancy During pregnancy Postpregnoncy Maximum drinks/occasion Prior to pregnancy During pregnancy

KASARI

M

SD

Min.

Med.

AAR AAD AAP

0.83 0.22

0.95 0.30

0 0

0.45

3.50

0.62

0.69

0

0.10 0.35

1.29 2.85

AOCR

3.84 2.14

2.07 1.92

0 0

4 2

9

3.61

2.04

0

3

MAXR

4.52

2.72

0

4

MAXD MAXP

2.09 3.98

1.89 2.19

0 0

1 4

MOX.

olcohol/doy

recognition

recognition

AOCD AOCP recognition

Postpreanoncy

7 10 10 6 10

Note. AA is a continuous variable: AA 2 1 .OO = overage of 2 2 drinks per doy of wine, beer, or liquor; AOC is the overage number of drinks reported on any drinking occasion; MAX is the moximum number of drinks on any drinking occasion; R refers to the month prior to pregnancy recognition, D to drinking during pregnancy, and P to drinking postpregnancy.

on the frequency and quantity of their alcohol use prior to pregnancy recognition, during pregnancy, and following the birth of the child.’ Estimates of caffeine ingestion, cigarette smoking, and other drug use during pregnancy were also collected. Three alcohol measures were collected reflecting varied patterns and levels of consumption reported by mothers. Means, standard deviations, medians, and range scores are presented in Table 1. The first alcohol level was estimated using Jessor, Graves, Hanson, and Jessor’s (1968) absolute alcohol (AA) score, which yields the average daily ounces of absolute alcohol consumed. Two drinks of wine, beer, or liquor is roughly equivalent to 1.0 oz (29.57 ml) of absolute alcohol or to an AA score of 1.0. A second alcohol measure, average drinks per occasion (AOC), was a simple count of the number of drinks the mother consumed per drinking occasion (Parker & Noble, 1977). A third measure, maximum number of drinks per drinking occasion (MAX), was calculated because of findings that infrequent heavy drinking was related to poorer child outcome (O’Connor et al., 1986; Streissguth, Barr, & Sampson, 1990). All alcohol levels obtained were considered estimates of actual exposure because they were based on maternal selfreport. Caffeine ingestion during pregnancy was calculated according to the procedure of Jacobson, Fein, Jacobson, Schwartz, and Dowler (1984). The ’ Recently, tioned during al., 1989).

investigators pregnancy,

and

have that

found valid

that women may data can be obtained

underreport at I-year

drinking postpartum

levels if ques(Jacobson et

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number of cups of coffee and tea was calculated along with the number of caffeinated soft drinks. Coffee was assigned a weight of 3, whereas tea and soft drinks were assigned a weight of 1. The sum of these weighted scores was used as the measure of caffeine consumption. Using this score, the average amount of caffeine consumed per day was calculated using the frequency weightings from the R. Jessor et al. (1968) system. Herbal teas and decaffeinated soft drinks were not used in calculations. The weighted daily average amount of caffeinated drinks consumed during pregnancy was 3.38 cups (SD = 5.97). Smoking during pregnancy was estimated by the number of cigarettes consumed per day (Dowler & Jacobson, 1984). Only 5 (11%) of mothers smoked during pregnancy (10-40 cigarettes per day). Thus, mothers were classified as nonsmokers or smokers and given a smoking score of 0 or 1. Drug use during pregnancy was estimated from each mother’s report of the number and kinds of drugs she consumed throughout pregnancy. Twelve mothers (27%) denied using any drugs at all. The remaining 32 mothers (73%) used over-the-counter preparations and/or prescription drugs. Five mothers (11%) used marijuana at regular intervals throughout pregnancy. None of the marijuana-using mothers took over-the-counter drugs. Marijuana was scored as a separate variable and was coded as a 1 for use and 0 for nonuse. All mothers denied taking heroin, amphetamines, PCP, LSD, cocaine, morphine, and mescaline. A frequency count of number of drugs taken during pregnancy was calculated. The average number of different drugs consumed by sample mothers was 1.25 (SD = 1.lO). A weighted drug score was calculated based upon potentially harmful effects of the drug on the fetus and its availability. Over-the-counter drugs were given a weight of 1, prescription drugs were weighted 2, and illegal drugs were weighted 3. The only illegal drug used by this sample was marijuana. The sum of the weighted scores was then compared to the drug frequency score. The correlation between the two was .92 so only the weighted drug score was used in data analysis. Demographic characteristics included child sex, race, mother’s IQ, maternal age, father’s education, and socioeconomic status. The length of time the mother nursed her infant was calculated as number of weeks. Average number of weeks nursing was 29 (SD = 18.50). Morher-lnfanf Meusures. All infants were scheduled for evaluation within 1 week of their first birthdays. An 8-min mother-infant interaction sequence was followed by the administration of the Bayley Scale of Mental Development and a physical examination. To assess mother-infant interaction, each infant was videotaped interacting with the mother in a laboratory playroom. The playroom was furnished with a sectional couch placed in a semicircle with a standard set of age-

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appropriate toys placed in the center of a carpeted area. There were four sequential episodes lasting 2 min each. Mothers were instructed to (a) allow the child to play alone with toys, (b) play with the infant with any of the toys, (c) assist the child in learning a simple cube-in-cup task, and (d) request that the child help in putting the toys away in a basket. The interaction episodes were subsequently viewed and rated by independent coders who were blind to any information regarding maternal alcohol consumption or infant characteristics. Child and maternal behaviors were rated using the Mother-Child Rating Scales (Crawley & Spiker, 1983). These scales consist of child and caregiver qualities rated on a 5-point Likert-type scale. One child variable was chosen to reflect possible behavioral differences that might be related to alcohol consumption. This variable was child negative affect. This variable includes child behaviors of whining, fussing, crying, screaming, frowning, and negative gestures (e.g., angrily throwing toys). The range of scores was from 1 to 5. A score of one reflected no expressed negative affect, whereas a score of 5 was characteristic of a child who exhibited very frequent frowns and negative gestures with some high intensity negative behavior, for example, one bout of active crying or temper tantrum. A middle score of 3 was descriptive of a child whose expression was not characteristically negative but who did use some whining, frowning, or negative gesturing interspersed occasionally throughout the session. The maternal qualities chosen were elaborativeness and stimulation value. Elaborativeness refers to the extent to which the mother follows or expands on the child’s self-initiated behaviors. A score of 1 indicates that the mother never elaborates on the child’s behaviors or responds in a negative way (e.g., prohibits child). A score of 3 indicates that the mother responds to many of the child’s behaviors by elaborating on them, but for only brief moments before returning to her own agenda. A score of 5 indicates that the mother responds to nearly all of the child’s independent behaviors by extending or expanding them, generally follows the child’s lead, and plays a more supportive role in the child’s play. Stimulation value refers to the degree to which the mother’s participation in play provides optimal cognitive stimulation for the child. A score of 1 indicates that the mother’s input does not provide the child with any stimulation. The mother may be highly intrusive or disorganized or with little comment. A score of 3 indicates the mother’s input may at times be intrusive, disorganized, or passive, but there may be clear moments of highly stimulating play as well. A score of 5 indicates that mother’s play is highly creative and appears optimally stimulating for the child’s developmental abilities. To check reliability during the course of the experiment, the interaction sessions of 9 different mothers and children (20% of entire sample) were rated by two coders working independently. A generalizability study was

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183

conducted to estimate interrater reliability. Generalizability studies are recommended for use with observational studies utilizing data of this nature (Algina, 1978; Mitchell, 1979) and yield intraclass coefficients (G coefficients) that control for observer bias. In this study, the G coefficients represent the ratio of subject score variance over the sum of subject variance plus rater by error variance. The G coefficient for the child negative affect measure was .86. The G coefficients for the individual maternal ratings were .89 for maternal elaboration and .99 for maternal stimulation value. Following the mother-infant interaction procedure, the Bayley Mental Scale of the Bayley Scales of Infant Development (Bayley, 1969) was administered to the infant by one of two experienced examiners who was unaware of the mother’s drinking history. A Bayley Mental Development Index (MDI) was calculated for each infant. After the Bayley assessment, all infants were examined by a pediatrician. A health history was taken, and a physical examination was conducted. The health history, and the Obstetrical Complications Scale (OCS) included questions covering pregnancy, labor, and delivery with emphasis upon medical complications (Littman & Parmelee, 1978). During the physical examination, the infant’s general appearance, height, weight, and neurological integrity were assessed. RESULTS Possible Covariates

In assessing possible causal associations between alcohol exposure and cognitive development in the infant, it is important to consider that these relations could be attributed to other causal factors. Possible covariates were selected for analyses based upon literature suggesting that they are associated with infant mental development. These variables included demographic measures of infant sex and race, maternal age and IQ, father’s education and social class. Obstetrical complications (OCS) and the number of weeks the mother nursed the infant were also considered. Zero-order correlations revealed that none of these variables was substantially correlated with Bayley MD1 (p < .lO) or with alcohol consumption. To assess their combined contribution, these variables were used as independent variables in a multiple regression analysis. The dependent variable was Bayley MDI. The squared multiple correlation (R’) was .12 with an adjusted RZ of - .05, F(8, 35) = 0.59 suggesting that these variables did not represent significant confounds and could be eliminated from analysis. A similar analysis was conducted examining the relation between other teratogens ingested by the mother during pregnancy and infant MDI. No individual teratogen met inclusionary criterion (p < .lO). The squared multiple correlation (R*) was .08 with an adjusted R* of - .Ol, F(4, 39) = 0.89,

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suggesting that, at least in this sample with relatively low ingestion levels, other teratogens did not significantly influence infant MDI. Although not correlated with MDI, caffeine was the only potential teratogen that was significantly correlated with alcohol ingestion during pregnancy (r = .37, p < .Ol). For this reason, models were tested with and without caffeine. The result was that caffeine contributed little to explaining the relation between alcohol ingestion and infant outcome. Therefore, models are presented with the caffeine variable omitted. Alcohol Consumption and Infant MD1 at 1 Year

The average MD1 score of sample infants on the Bayley Mental Scale was 110.20 (SD = 10.20, range = 91-134). These scores are average to superior with a slightly restricted range. In order to estimate the magnitude of effects of drinking during pregnancy on infant MDI, further analyses were conducted. Because mothers reported relatively low levels of drinking during pregnancy, the sample was divided into two groups, those classified as nondrinkers and those who drank some during pregnancy. The nondrinking group was composed of women with an AA score of less than or equal to .lO or a MAX/AOC score of 2 or fewer drinks. The drinking group was composed of women with an AA score. of greater than .lO or a MAX/AOC score of greater than 2. Mean MD1 scores were compared using t tests. Results are presented in Table 2 for each alcohol measure. The strongest relation between alcohol use during pregnancy and infant MD1 was found using the average drinks per occasion score (AOCD). Infants of mothers who reported drinking 2 or fewer drinks per occasion had a mean MD1 score of 114 (SD = 9.29); infants of mothers drinking more had a TABLE 2 Mean

Bayley

MDI

Scares

in Relation During

Alcohol

Score

Average absolute alcohol/day (AAD) Nondrink c .lO Drink > .lO Averoge drinks/occasion (AOCD) Nondrink TG 2 drinks Drink > 2 drinks Moximum drinks/occasion Nondrink YG 2 drinks Drink Note.

lp

df =

42. “p

= .05.

Alcohol

Consumption

Patterns

Pregnancy n

M

SD

t

20 24

113.10 107.79

a.99

i ,788

27 17

113.59

9.29 9.46

3.03”’

104.38

27

112.70

10.25

2.13”

17

106.23

9.05

10.70

(MAXD)

> 2 drinks

= .oa.

to Maternal

***p

=

.Ol.

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COGNITION

mean MD1 of 104 (SD = 9.46), r(42) = 3.03, p < .Ol. Similar but less significant differences were obtained using the maximum drinks per occasion score (MAXD) and the AA (AAD) score. Infant MD1 was then compared to the IQ of the mother as measured by the Shipley Institute of Living Scale. The mothers’ IQs were comparable across comparison groups with the drinking group mothers having a mean IQ of 119 (SD = 6.85), and the nondrinking group mothers having a mean IQ of 118 (SD = 4.81), f(42) = .71, p = .44. Comparing mean infant MD1 scores obtained by grouping subjects according to AOCD levels with mean mother IQs revealed a significant difference. The mean MD1 scores of infants whose mothers were in the drinking group was 15 points lower than the average IQs of their mothers. In contrast, there was only a 4-point difference between the mother and infant scores in the group composed of mothers who were classified as nondrinkers, t(42) = 2.22, p < .05. Model:

Alcohol

Use and Infant

Mental

Development

Figure 1 shows the model studied for the association among alcohol, motherinfant variables, and infant mental development. The model is shown as a path diagram using the conventional method of placing measured variables in rectangles and factors, or latent variables, in ovals. The maternal alcohol variables, average drinks per occasion prior to pregnancy recognition, during, and following pregnancy (AOCR, AOCD, AOCP) make up a common latent

A E6

A E5

l

p < .05, tw*tiled

test

Figure 1. Model for moternol alcohol use, infant affect, mother-infant interaction, and infont mental development. Meosured variobles are Vl-V7. All other variables represent hypothesized constructs: Fl, F2 represent the common factors, maternal alcohol consumption and moternol interaction; El-E7 represent errors or residuals One-way arrows are structural by an asterisk. Unidirectional V5 is fixed at 1.0.

in variables; ond D2 represents disturbance regression coefficients. Each free parameter orrows from E and D have fixed 1.O values,

or resrduols in Factor F2. to be estimated is shown and one arrow from F2 to

186

O’CONNOR,

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variable labeled alcohol consumption. The average drinks scores were chosen as variables because the AOC scores had more normalized distributions than the AA or maximum drinks scores and because average drinks scores have been found to be more powerful predictors of potential cognitive effects (Parker & Noble, 1977). One-way arrows represent hypothesized influences of independent variables on dependent variables. Maternal elaboration and stimulation were assumed to be indicators of a latent variable labeled maternal interaction. These variables were highly correlated (r = .70). Errors in measured variables are given E designations, residuals in factors are labeled D. Before model testing, data were analyzed for univariate and multivariate kurtosis to evaluate normality of variable distributions. Univariate kurtosis ranged from - .90 to 1.30. Mardia’s normalized estimate was 2.07 with a kappa of .ll , so data were not transformed further for analysis, and a maximum likelihood solution was used. Table 3 is the covariance matrix of study variables; included in this table are zero-order correlations. Figure 2 presents the results of model estimation examining the association between alcohol consumption, mother-infant interaction, and infant MDI. Parameter estimates are presented after transforming the representations into completely standardized solutions. In these solutions, each variable has been transformed so that its variance is 1.0. Thus, regression coefficients can be interpreted as beta coefficients and covariances as correlations. The statistical significance of the parameter estimates was tested using normal theory z tests. Significant estimates are presented with asterisks beside them. The goodnessTABLE Covorionce 1

Vorioble Prior

to pregnancy

Pregnancy

(AOCR)

(AOCD)

3 Motrix

2

3

3.02 (0.76)’

3.70 (1.00)

(AOCP)

3.22 (0.76)’

2.57 (0.66)’

4.15 (1 In)

Child

affect

0.81 (0.35)’

0.77 (0.36)’

0.28 (0.12)

Moternol Moternol lnfont

-0.59 (-0.29)

elaboration stimulation

- 0.59 (-0.28) -11.11 (-0.52)’

MDI

Note. Numbers < .05.

lp

in porentheses

5

6

7

4.32 (1 .OO)

Postpregnancy negotive

4

ore

1.25 (1 .OO) 0.94

- 0.20 (-0.10) -0.38

-0.21 (-0.10) -0.11

- 0.35 (-0.32)’ -0.64

(1.00) 0.70

1.03

(-0.19) - 8.66 (-0.44)’

(-0.05) - 9.55 (-0.45)’

(-0.56)’ -4.14 (-0.36)’

(0.70)’ 4.00 (0.40)’

(1.00) 4.27 (0.41)’

simple

correlations

(r).

104.12 (1.00)

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COGNITION

of-fit chi square was x2(11, N = 44) = 12.65, p = .31, indicating that the model fit the data. The Bentler-Bonnet normed fit index for the model was .92. All parameter estimates were significant with the exception of the one representing the association between maternal alcohol consumption (Fl) and maternal interaction behavior (F2). In order to understand better whether or not alcohol ingestion during different time periods may have affected infant outcome differently, two final models were tested. In one model, presented in Figure 3, the prior to pregnancy recognition drinking score (Vl) and the during pregnancy drinking score (V2) were combined to form a latent variable labeled prenatal alcohol consumption (Fl). This variable was substituted into the model and yielded

p < .05, wm-tatled

l

Figure 2. Model for rnoternol development. Unidirectional

alcohol orrows

use, infont affect, mother-infont represent standardized beto

interaction, coefficients.

ond

test

infant

mental

El

l

Figure 3. Model exomining mother-infont interaction,

and

the ossociotion infant mentol

between prenatol development.

moternol

p

<

.05.

alcohol

two-talled

test

use,

infant

affect,

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AND

KASARI

l

Figure 4. Model examining mother-infant interaction,

the association and infant mental

between postnotal development.

p < .05, two-tailedtest

maternal

alcohol

use,

infant

affect,

results similar to those in Model 1, x2(6, N = 44) = 6.31, p = .38 (BentlerBonnet normed fit index = .95). Once again, all parameter estimates yere significant except the one reflecting an association between alcohol consumption and maternal interaction. A final model examined similar relations between variables, this time substituting the postpregnancy drinking score (V3) as the independent variable. This model is presented in Figure 4. This model was also found to fit the data, x2(3, N = 44) = 3.32, p = .34 (BentlerBonnet normed fit index = .95); However, the parameters representing associations between maternal postnatal drinking (V3) and infant negative affect (V4) and maternal postnatal drinking (V3) and maternal interaction (F2) were not significant. DISCUSSION This experiment demonstrates the importance of considering infant temperament and the mother-infant relationship in the study of alcohol effects on the infant. Although common sense suggests that behavioral or environmental influences must be great, particularly in a group of infants whose mothers are moderate or social drinkers, research investigators have ignored these influences or have treated them as covariates. In this experiment, maternal alcohol use appeared to influence the infant’s behavior. Irritability or negative affect described in newborns of moderate drinkers was also found in our sample of children at 1 year. Furthermore, comparison of prenatal and postnatal effects of alcohol exposure on negative affect suggests that prenatal exposure is teratogenic on infant behavior. These results are particularly striking given that postnatal exposure was highly correlated with prenatal

MATERNAL

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exposure. It is also of interest that prenatal exposure impacted upon infant affect but not on maternal interaction, suggesting that, at least at the levels of consumption reported by this sample, it was the child’s behavior rather than the mother’s drinking that affected the quality of the stimulation that the mother provided in interaction. Thus, it appears that infant affect may mediate the effect of alcohol exposure on cognitive outcome. Prenatal alcohol exposure impacted negatively on infant affect which, in turn, influenced environmental stimulation needed for optimal cognitive development. Maternal drinking during pregnancy was also found to relate directly to infant mental development. This finding replicates the results of the Seattle Longitudinal Prospective Study and suggests that neurobehavioral effects are directly associated with even moderate levels of prenatal alcohol exposure in relatively low-risk, middle-class populations (Streissguth, Barr, Sampson, Darby, & Martin, 1989). In addition, mean alcohol consumption levels reported during pregnancy by the current sample are consistent with those reported in the Seattle study, although the ranges are restricted. The restrictions in range may be related to differences in sample selection, or to underreporting of heavier drinking due to the stigma associated with drinking during pregnancy. Because mothers in this sample may have underreported consumption levels, mean alcohol scores for which effects were found should not be used to set thresholds for safe or unsafe levels of drinking. Maternal drinking postnatally was also found to relate directly to infant mental development. This variable represents the environmental influence of alcohol consumption directly on infant outcome. This influence did not appear to be mediated by the direct effect of drinking on the maternal interaction variables chosen for study, but may be related to other maternal variables associated with drinking that may influence the cognitive behaviors of the infant. For example, maternal personality or affective factors associated with drinking, such as feelings of low self-esteem or depressed mood, were not examined in this experiment. A positive finding was that none of the infants in the experiment was functioning in the mentally deficient range. Nevertheless, if one considers the mother’s IQ as a rough estimate of genetic potential, a depressive effect on infant ability may be speculated. The average mental score of infants of mothers who were abstinent or light drinkers during pregnancy was similar to the average IQ of their mothers. In contrast, the average mental score of infants whose mothers drank more was 15 points below the average IQ of their mothers. Although the findings reported in this experiment provide evidence of alcohol’s effect on infant affective response and concomitant maternal behavior, a note of caution regarding path analysis and the interpretation of these causal models is in order. Although this procedure allows one to test the influence of variables upon one another according to the theoretical plan, it does not necessarily allow for the discovery of definitive causes. In this ex-

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