the effects of prenatal care utilization and maternal risk factors on

THE EFFECTS OF PRENATAL CAREUTILIZATION AND MATERNAL RISKFACTORS ON PREGNANCYOUTCOME BETWEEN MEXICANAMERICANS AND NON-HISPANICWHITESHector Balcazar, MS, PhD, Judith Hartner, MD, MPH, and Galen Cole, PhD, MPHTempe, Arizona and Atlanta, Georgia

This study evaluates the effects of prenatalcare classification and levels of maternal riskstatus on pregnancy outcomes in MexicanAmericans and non-Hispanic whites in Arizona.All live birth certificates from 1986 and 1987were reviewed yielding a total population of101 206 (26 827 Mexican Americans). The ade-quacy of prenatal care was evaluated based onan index that includes six prenatal care groups.Two levels of maternal risk status (low andhigh) were defined based on a series ofmaternal risk factors. Overall, Mexican Ameri-cans had a greater proportion of maternal riskfactors and a greater proportion of motherswith inadequate or no prenatal care comparedwith non-Hispanic whites. Prematurity andmacrosomia were more prevalent than lowbirthweight in Mexican Americans. Low-riskstatus and adequate prenatal care regardlessof ethnicity were found to be associated with alower prevalence of low birthweight and pre-term delivery. Whites, however, had a greater

From the Department of Family Resources and HumanDevelopment, Arizona State University; Preventive Services,Maricopa County Department of Health Services; and Re-search and Evaluation Branch, Centers for Disease Control andPrevention, Atlanta, Georgia. This research was supported byfunds from the Faculty Grant-in-Aid Program, College of LiberalArts and Sciences, Arizona State University, Tempe, Arizona.Requests for reprints should be addressed to Dr HectorBalcazar, Dept of Family Resources and Human Development,Arizona State University, Tempe, AZ 85287-2502.

variation in the prevalence of low birthweightassociated with changes in prenatal care utili-zation and maternal risk status compared withMexican Americans. Finally, logistic regres-sion analysis showed an independent effect ofprenatal care, maternal risk status, maternalage, and maternal birthplace in predicting theoverall low birthweight rate in Mexican Ameri-cans. The implications of these results arediscussed relative to the usefulness of prenatalcare as a health-care intervention in MexicanAmericans. (J NatI Med Assoc. 1993;85:195-202.)

Key words * prenatal care * pregnancy outcomematernal risk factors * low birthweight

* Mexican Americans

Previous studies that have addressed perinatal healthproblems in Mexican Americans have been consistentin reporting overall low prenatal care utilization andrelative low prevalence of low birthweight comparedwith non-Hispanic whites.1 These two findings seem topose a paradox given the disadvantaged socioeconomicstatus, the low educational levels, and the dispropor-tionate distribution of certain perinatal risk factorspresent in this minority group.2 However, large scalepopulation-based studies that have looked more closelyinto the study of low birthweight in Mexican Americanshave reported that the risk for low birthweight is notequally distributed among subgroups of Mexican

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TABLE 1. DESCRIPTIVE STATISTICS OF INDICATORS OF BIRTH OUTCOME BY LEVELS OF MATERNAL RISKBETWEEN MEXICAN AMERICANS AND WHITES

Low Risk High RiskMexican Mexican

Americans Whites Americans Whites

No. births 5161 22097 20097 49510Preterm (<37 weeks) 7.7% 5.4% 11.5% 9.3%Low birthweight (<2500 g) 3.7% 3.8% 7.1% 7.3%Macrosomia (>4000 g) 8.7% 11.6% 9.5% 11.9%Mean birthweight (g) 3389 3450 3332 3376Mean gestational age (weeks) 39.2 39.5 39.1 39.3

Americans.34 Changes in the risk of low birthweighthave been associated with patterns of prenatal careutilization, maternal age, maternal education, andmaternal birth place (Mexico versus United States)." 3'4In addition, these studies have identified other perinatalproblems in Mexican Americans that have not beenpreviously considered by empirical studies, namely theproblem of prematurity (gestational age less than 37weeks) and the problem of macrosomia (birthweight>4000 g).3'4When addressing the problem of low birthweight in

the Mexican-American population, there is a need tocarefully evaluate the importance of prenatal careutilization and the distribution of maternal risk factorsdue to the fact that these are known factors associatedwith the risk of low birthweight.5'6 Thus, the evaluationof these factors in population-based studies of MexicanAmericans is necessary in order to provide answers tothe epidemiologic paradox observed in this group.

This type of research could elucidate the roles ofprenatal care utilization and maternal risk factors onpregnancy outcomes in Mexican Americans as a basisfor recommending more appropriate public healthinterventions in this minority group. Unfortunately,there has been no extensive evaluation of the effects ofadequate prenatal care utilization and maternal riskfactors on pregnancy outcomes in Mexican Americans.This study was designed to evaluate the effects ofprenatal care utilization and maternal risk factors onoutcomes of pregnancy, namely low birthweight,preterm delivery, and macrosomia in Mexican Ameri-cans versus non-Hispanic whites.

METHODSDatabaseThe data for this research were collected from state

data files containing all live birth certificates for thestate of Arizona, for the years of 1986 and 1987. A total

of 101 206 live births were analyzed. We decided to usethe non-Hispanic white population as a comparisongroup. For this study, only the ethnic origin of themother was considered. Within Hispanics, only those ofMexican origin were considered for analysis. Theanalysis included 26 827 Mexican Americans and74 379 whites.

MeasuresSeveral maternal risk factors were defined from the

birth certificates. A low level of risk was defined if therewas no maternal risk factor present. Conversely, a highlevel of risk was defined if one or more maternal riskfactors were present. The risk factors used in this studywere:* unmarried,* <9 years of formal education,* at least one reported complication of pregnancy,* at least one reported illness,* at least one reported labor complication,* one or more previous fetal deaths or pregnancy

terminations, and* age at previous pregnancy history (risk categories

includes the following age groups: 10 to 15 years oldregardless of previous pregnancies, 16 to 19 yearsold with one or more previous pregnancies, 20 to 24years old with three or more previous pregnancies,25 to 29 years old with four or more previouspregnancies, 30 to 34 year old with five or moreprevious pregnancies, 35 to 39 years old with sevenor more previous pregnancies, 30 to 39 years oldwith no previous pregnancies, and >40 years old).7For the classification of prenatal care utilization, the

"Gindex" developed by Alexander and Cornely wasused.7 This index takes into account three factors: themonth when prenatal care began, the number of prenatalcare visits, and the duration of pregnancy. The Gindexidentifies six prenatal care utilization groups: intensive,

196 JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 85, NO. 3

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TABLE 2. DISTRIBUTION OF LEVELS OF PRENATAL CARE UTILIZATION BY LEVELS OF MATERNAL RISKBETWEEN MEXICAN AMERICANS AND WHITES

Low Risk High RiskMexican Mexican

Americans Whites Americans WhitesLevel ofPrenatal Care No. % No. % No. % No. %

Intensive 373 6.9 1903 8.3 1269 5.9 5077 9.8Adequate 2543 47 15 019 66 8059 37.6 29 431 57Intermediate 1545 28.6 4111 18.1 6400 29.9 10 554 20.5Inadequate 583 10.8 918 4 3384 15.8 3722 7.2No-care 117 2.2 146 0.6 985 4.6 726 1.4Missing/unknown 241 4.5 687 3 1328 6.2 2085 4.1Totals 5402 22 784 21 425 51 595

TABLE 3. PREGNANCY OUTCOME INDICATORS BY LEVELS OF MATERNAL RISK FACTORS AND PRENATALCARE UTILIZATION PATTERNS BETWEEN MEXICAN-AMERICANS AND WHITES

Preterm Low Birthweight MacrosomiaLow Risk High Risk Low Risk High Risk Low Risk High RiskM W M W M W M W M W M W

Intensive 9.7 5.1 10.2 9 3.8 3.7 5.1 6.7 9.9 12.8 13.4 14.1Adequate 6.4 4.7 9.7 7.8 3.3 3.3 6.4 5.8 8.7 12 10.4 12.7Intermediate 8.5 6.6 11 11 3.9 4.7 6.4 8.8 9.1 10.7 9.1 9.8Inadequate 8.6 11 15.2 16.5 5.3 6.8 8.6 12.7 7.5 9 7.6 9.2No-care 13.7 13.7 19.2 16 4.3 12.3 13.4 18.2 3.4 6.2 6.7 6.2

Risk Ratios*

Group Preterm Low BirthweightMexican Americans

Inadequate/no-care low risk Risk ratio = 1.46 (1.09-1.78) Risk ratio = 1.57 (1.06-2.10)Adequate high risk Risk ratio= 1.50 (1.28-1.74) Risk ratio= 1.97 (1.54-2.34)Inadequate/no-care high risk Risk ratio=2.49 (2.06-2.76) Risk ratio=2.97 (2.34-3.58)

WhitesInadequate/no-care low risk Risk ratio= 2.41 (1.99-2.85) Risk ratio= 2.29 (1.77-2.72)Adequate high risk Risk ratio= 1.65 (1.47-1.72) Risk ratio= 1.78 (1.55-1.85)Inadequate/no-care high risk Risk ratio= 3.48 (3.08-3.70) Risk ratio=4.14 (3.66-4.52)

*Risk ratios and 95% confidence intervals were calculated relative to the adequate low-risk group.

adequate, intermediate, inadequate, no-care, and miss-ing/unknown. These groups are defined by successiveintervals of gestational age at delivery and the combina-tion of the trimester in which prenatal care began andthe number of prenatal care visits.

For the purpose of this study, gestational age wascomputed based on the last normal menses and the dateof birth of the infant. Gestational age was expressed incompleted weeks counted from the first day of the lastnormal menses to the date of delivery. If the day of thelast normal menses was missing, the 15th day of thatmonth was used. Studies that have used this approach

have not reported significant changes in the direction oftheir results.7

AnalysesThe indicators of pregnancy outcome evaluated in

this study were the following: low birthweight (birth-weight <2500 g), preterm delivery (gestational age<37 completed weeks), macrosomia (birthweight>4000 g), mean birthweight, and mean gestational age.For the computation of mean values of birthweight andgestational age, cases with gestational ages -52 weeksand birthweight >7000 g were omitted. The missing/


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TABLE 4. MEAN VALUES OF BIRTHWEIGHT AND GESTATIONAL AGE BY LEVELS OF MATERNAL RISKFACTORS AND PRENATAL CARE UTILIZATION PATTERNS BETWEEN MEXICAN AMERICANS AND WHITES

Birthweight (g) Gestational Age (Weeks)Low Risk High Risk Low Risk High Risk

M W M W M W M W

Intensive 3413 3496 3407 3417 39 39.7 39.4 39.4Adequate 3402 3466 3367 3422 39.3 39.5 39.2 39.3Intermediate 3390 3400 3332 3303 39.2 39.5 39.1 39.1Inadequate 3335 3357 3271 3214 39.4 39.5 39 38.9No-care 3280 3126 3140 3079 38.7 38.7 37.9 38.1

Abbreviations: M = Mexican Americans and W = whites.

unknown prenatal group also was omitted for thecalculation of prevalence rates associated with thepregnancy outcome indicators. The analysis associatedwith adolescents does not include the risk factor for ageand previous pregnancy history for defining low versushigh levels of maternal risk factors.

Several analyses were performed in order to describethe effect of prenatal care classification and levels ofmaternal risk on pregnancy outcomes in severalsubgroups of Mexican Americans and non-Hispanicwhites. Relative risks and 95% confidence intervalswere calculated for the indicators of low birthweightand preterm delivery. The adequate prenatal carelow-risk group was used as the control group for thecalculation of the risk ratios and confidence intervals.

Finally, logistic regression analysis was performedon the Mexican-American subgroup in order to evaluatethe independent effect of prenatal care utilization(adequate versus no-care or inadequate care), maternalrisk factors (low versus high), maternal age (<20 yearsold versus ¢20 years old), and maternal birth place(Mexico versus United States). The data were analyzedusing the SAS statistical software (SAS Institute Inc,Cary, North Carolina) on an IBM mainframe computer.

RESULTSDescriptive statistics of birth outcomes according to

low and high levels of maternal risk between MexicanAmericans and whites are shown in Table 1. For theMexican American group, 20.4% of the births were tomothers classified as low risk and 79.6% were tomothers classified as high risk. For the white group,30.8% of the births were to mothers classified as lowrisk and 69.2% were to mothers classified as high risk.As indicated in Table 1, the low-risk groups in bothMexican Americans and whites had better outcomesrepresented by the lower percentage of births classifiedas preterm, low birthweight, and macrosomia. In

addition to these indicators, differences in meanbirthweight also were observed between the low- andhigh-risk groups. White infants of mothers classified inthe high-risk group had a mean deficit of 74 g comparedwith babies in the low-risk group. The same trend wasobserved for Mexican Americans; however, the deficitin mean birthweight of the high-risk group comparedwith the low-risk group was only 57 g. There were nosignificant differences between low- and high-riskgroups related to the mean values of gestational age inboth ethnic groups. Within high-risk groups, thegreatest prevalence of negative outcomes in MexicanAmericans was in preterm delivery, and the lowest wasin low birthweight. For whites, the greatest prevalencein the high risk group was associated with macrosomia.

The percentage distribution of levels of prenatal careby maternal risk categories of low- and high-risk forboth Mexican Americans and whites are described inTable 2. The low-risk groups in both MexicanAmericans and whites had a lower number of casesdistributed in the inadequate and no-care categories ofprenatal care compared with their high-risk counter-parts. Mexican Americans had greater percentages ofmothers in the inadequate and no-care groups thanwhites in both risk categories.

Effect of Prenatal Care and Maternal Riskon Pregnancy OutcomesThe results of the prevalence of low birthweight,

preterm, and macrosomia by levels of prenatal careutilization and maternal risk categories between Mexi-can Americans and whites are presented in Table 3. Theprevalence of preterm delivery and low birthweight wasgreater for the high-risk group than for the low-riskgroup for all levels of prenatal care utilization. Thegreatest prevalence of preterm delivery and lowbirthweight was observed in the high-risk groupsreceiving no prenatal care in both ethnic groups. These


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TABLE 5. PRETERM AND LOW BIRTHWEIGHT BY LEVELS OF MATERNAL RISK FACTORS AND PRENATALCARE UTILIZATION PATTERNS BETWEEN MEXICAN-AMERICAN AND WHITE ADOLESCENTS

Preterm Low BirthweightNo. % Risk Ratio* % Risk Ratio

Adequate low riskMexican Americans 247 8 3.6Whites 815 6.3 6

Adequate high riskMexican Americans 1396 11.8 1.46 (0.95-2.04) 9.4 2.59 (1.36-4.53)Whites 2352 9.3 1.47 (1.08-1.79) 7.3 1.22 (0.91-1.58)

Inadequate/no-care low riskMexican Americans 152 12.5 1.54 (0.74-3.02) 9.2 2.52 (1.14-5.39)Whites 185 8.6 1.35 (0.81-2.07) 5.4 0.89 (0.42-1.85)

Inadequate/no-care high riskMexican Americans 1191 19.8 2.44 (1.61-3.52) 11.6 3.20 (1.74-5.79)Whites 999 17 2.66 (1.97-3.39) 15.3 2.54 (1.86-3.32)


results are confirmed by the risk ratios and 95%confidence intervals of the inadequate/no-care high riskgroups shown in the bottom of Table 3. In both lowbirthweight and preterm delivery, the risk ratios of theinadequate/no-care high-risk white group were signifi-cantly higher than for Mexican Americans.

The results of the relative risk ratios also confirmed theindependent effect of both poor prenatal care use andmaternal risk on the outcomes of low birth weight andpreterm delivery. The following contrasts were used forevaluating the effect of prenatal care: inadequate/no-carelow risk versus adequate low risk and inadequate/no-carehigh risk versus adequate high risk. For evaluating theeffect of maternal risk, the following contrasts were used:adequate low risk versus adequate high risk andinadequate/no-care low risk versus inadequate/no-carehigh risk. The effect of prenatal care on preterm deliveryand low birthweight is demonstrated by comparing thedifference in prevalence between these two indicatorsfrom Tables 1 and 3. For example, the range ofprevalences of preterm delivery of 13.7 and 19.2 betweenboth low- and high-risk groups with no-care prenatal carefrom Table 3 exceeds the greatest prevalence of pretermdelivery of 11.5% in Mexican Americans from Table 1. Asimilar pattern is seen for low birthweight.One striking result observed in Table 3 was in

relation to the relatively low prevalence of 4.3% of lowbirthweight in the Mexican-American low-risk groupreceiving no prenatal care. Furthermore, the increase inthe prevalence of low birthweight in Mexican-American mothers in the low-risk group only fluctuatedfrom 3.3% to 5.3% throughout the levels of prenatalcare utilization.

For macrosomia, Table 3 also shows that there wasan increase in the prevalence of this condition in thehigh-risk group as opposed to the low-risk group. Thegreatest prevalences were observed in the intensivegroup of prenatal care utilization in both MexicanAmericans and whites.

The effect of classification of prenatal care utilizationand levels of maternal risk on birthweight and gesta-tional age is shown in Table 4. Mean birthweight valuesdecreased within levels of maternal risk from theintensive to the no-care prenatal group in both MexicanAmericans and whites. Interestingly, the Mexican-American group had greater mean birthweights in theno-care group in both low- and high-risk categories thanwhites. Conversely, whites had greater mean birth-weights in the intensive and adequate levels of prenatalcare within levels of maternal risk. The effect ofprenatal care classification on birthweight beyond theeffects of maternal risk between Mexican Americansand whites can be evaluated by comparing Tables 1 and4. Variation in mean birthweight among prenatal carecategories within low and high risk levels was greater(Table 4) than the variation in mean birthweightobserved between low and high maternal risk regardlessof prenatal care (Table 1). In reference to gestationalage, small differences in mean gestational age wereseen for the no-care group compared with the otherprenatal care levels. Differences between high and lowlevels of maternal risk in the no-care group were lessthan 1 week gestation for both ethnic groups.To assess the impact of prenatal care classification

and levels of maternal risk on pregnancy outcomes inMexican-American and white adolescents, the preva-


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TABLE 6. PRETERM AND LOW BIRTHWEIGHT BY LEVELS OF MATERNAL RISK FACTORS AND PRENATALCARE UTILIZATION PATTERNS BY MATERNAL BIRTH PLACE WITHIN MEXICAN AMERICANS

Preterm Low BirthweightNo. % Risk Ratio* % Risk Ratio

Adequate low riskMexico-born 695 5.2 3.4United States-born 1829 7 3.2

Adequate high riskMexico-born 2583 9.3 1.80 (1.28-2.50) 5.5 1.58 (1.03-2.16)United States-born 5407 9.9 1.41 (1.16-1.67) 6.9 2.16 (1.63-2.68)

Inadequate/no-care low riskMexico-born 348 7.5 1.44 (0.89-2.19) 5.2 1.49 (0.85-2.29)United States-born 348 11.5 1.64 (1.15-2.20) 5.2 1.63 (0.97-2.62)

Inadequate/no-care high riskMexico-born 1883 11.9 2.30 (1.66-3.15) 7.5 2.16 (1.41-3.08)United States-born 2460 19.3 2.75 (2.25-3.19) 11.4 3.58 (2.72-4.44)


lence of preterm delivery and low birthweight wasanalyzed based on these factors. The results aredescribed in Table 5. Note that the classification ofprenatal care is based on two levels: adequate versusinadequate and no-care. This classification was usedbecause of sample size limitations and in order tosimplify the analysis.

The evaluation of the independent effects of prenatalcare and maternal risk is based on the risk ratios and 95%confidence intervals shown in Table 5. Statisticallysignificant independent effects are observed for prenatalcare use and maternal risk in some of the contrasts for lowbirthweight and preterm delivery in Mexican Americansand whites. The same contrasts used in the previousanalysis listed in Table 3 were used to evaluate theindependent effects of prenatal care use and maternal risk.Within low- and high-risk groups, there was an increasein the prevalence of preterm delivery and low birthweightin the inadequate/no-care group compared with theadequate group in both Mexican Americans and whites.Similarly, within levels of prenatal care utilization, therewas an increase in the prevalence of preterm delivery andlow birthweight in the high-risk group versus the low-riskcounterpart.

The next analysis evaluated the effect of prenatal careclassification and levels of maternal risk on lowbirthweight and preterm delivery by maternal place ofbirth within the Mexican American group. Table 6 showsthe prevalence of these pregnancy outcomes by differentsubgroups as well as the risk ratios and 95% confidenceintervals. Overall, regardless of maternal risk or prenatalcare classification, mothers born in the United States hadgreater prevalences of preterm delivery and low birth-

weight than mothers born in Mexico. Based on the riskratios and 95% confidence intervals shown for theMexico-born sample, there was no effect of prenatal careuse on the indicators of low birthweight and pretermdelivery. Note that the lower 95% confidence intervals ofsome of the contrasts are lower than 1 and overlap withthe risk ratios for the Mexico-born sample. For theUS-born sample, there was an independent effectobserved in both prenatal care use and maternal risk inboth low birthweight and preterm delivery.

Logistic Regression Analysis of LowBirthweight in Mexican Americans

Finally, the last analysis used logistic regression totest the independent effects on low birthweight for thefollowing variables: prenatal care utilization, maternalrisk factors, maternal age, and maternal birth place inthe Mexican-American population. The results of thisregression analysis are shown in Table 7. All regressioncoefficients are highly significant and in the directionexpected. The negative signs for the coefficientsassociated with gestational age and maternal agerepresent an increased risk for decreasing values ofgestational age and maternal age (<20 years). Thepositive signs for the coefficients associated with theno-care and inadequate groups, for having a maternalrisk factor present, and for being US-born reflect anincrease in the risk of low birthweight if thesecharacteristics were present in Mexican Americans inthis population.

DISCUSSIONThe results of this study demonstrate that Mexican


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Americans, when compared with non-Hispanic whites,have a greater proportion of maternal risk factorsrepresented by social and medical characteristics. Theresults agree with the previously reported observationthat Mexican Americans, in general, use prenatal careservices less frequently than non-Hispanic whites.'

Low-risk status was found to be associated with alower prevalence of low birthweight, preterm delivery,macrosomia, and with a greater mean birthweight inboth Mexican-American and white women. Prenatalcare utilization and maternal risk status were found tohave an independent effect on pregnancy outcomes inboth Mexican Americans and whites. The greatesteffect on changes in low birthweight and pretermdelivery prevalences was most evident within thehigh-risk groups. A note of caution should be givenwhen interpreting the results of the independent effectsof medical risk factors. This study used data from birthcertificates to identify medical risk factors. The qualityand the type of information derived from birthcertificates is limited.

The independent effect of prenatal care utilizationalso should be interpreted with caution due to the factthat potential social and maternal risk factors were notaccounted for when evaluating changes in prevalence oflow birthweight and preterm delivery. Research isneeded to determine the relative contribution ofsocioeconomic factors and factors associated withfamily values, traditions, and beliefs, which could havebeen responsible for the difference in pregnancyoutcomes observed within and between ethnic groups.Our findings of preterm delivery also should beinterpreted with caution. Gestational estimation basedon the date of the last normal menses from vital recordsis subject to errors in completeness and quality.8'9Furthermore, errors in gestational age estimation are ofparticular concern for women belonging to specialgroups such as those in which prenatal care is poor ornonexistent.8'9 Quality and completeness issues werenot explored in this investigation. Thus, qualityassurance issues need to be addressed when evaluatingpremature delivery as a public health problem inMexican Americans.

The results of ethnic variations in prenatal careutilization require further investigation. Whites had agreater variation in the prevalence of low birthweightand in mean birthweight associated with changes inprenatal care utilization compared with Mexican Amer-icans in both low- and high-risk categories. Theliterature indicates a growing concern for the need toevaluate the adequacy of prenatal care interventions in

TABLE 7. LOGISTIC REGRESSION ANALYSIS FORSELECTED INDEPENDENT VARIABLES AND THEIRASSOCIATION WITH LOW BIRTHWEIGHT IN THE

MEXICAN-AMERICAN POPULATION*

Regression StandardVariable Coefficient Error P Value

Gestational age -0.18 0.006 0.0001Prenatal care utili- 0.17 0.027 0.0001

zation (no-careand inadequatecombined)

Maternal risk factor 0.58 0.081 0.0001(risk factor pre-sent)

Maternal age -0.04 0.023 0.03(<20 yrs old)

Maternal birthplace 0.30 0.059 0.0001(United States-born)

*Total N = 25072, low birthweight <2500 g, n for lowbirthweight = 1599.

Mexican Americans given the differential response invariations in pregnancy outcomes observed in theMexican-American group.1"0 In this regard, the resultsof the low prevalence of low birthweight throughout therange of prenatal care utilization are of particularinterest. There is the possibility that prenatal care use insome Mexican-American subgroups is a reflection ofmaternal behaviors and attitudes rather than a health-care intervention.1 As an indicator of behaviors andlifestyle, seeking prenatal care reflects the mother'spersonal beliefs, values, and actions about the impor-tance of her pregnancy. Thus, low use of prenatal caremay indicate low desirability or value of prenatal careby the Mexican-American mother.' Consequently,prenatal care as an intervention might not necessarilypositively affect the outcome of pregnancy. Publichealth programs associated with prenatal care utiliza-tion in Mexican Americans should be carefully de-signed so that they will not alter Mexican values andbeliefs that are protective of negative outcomes such aslow birthweight.

Research is needed to identify what factors (eg,cultural, social, and medical) are responsible for thefavorable prenatal experience in the Mexican-Americangroup. The new information that this type of researchwill bring could help identify effective screeningprograms for those women at risk for negativepregnancy outcomes. Studies are also needed to identifythe reasons why some Mexican-American women seekprenatal care as well as the circumstances surrounding


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the type of utilization of prenatal care. The same type ofdata are needed in regard to those Mexican Americanwomen who are not using prenatal care services.The problem of macrosomia in Mexican Americans

requires further investigation. The greater prevalencesof macrosomia in the intensive and adequate prenatalgroups may be an indication that some Mexican-American women are being served more extensivelybecause of their particular maternal characteristics.Unfortunately, we do not know what those maternalcharacteristics are in the low- and high-risk groups thatmay predispose women to seek prenatal care.The results of the analysis done by maternal birth

place within Mexican Americans agrees with previousstudies that have reported data on pregnancy outcomesin these subgroups.1 3 Women born in the United Statesshowed a greater variation in prevalence of pretermdelivery and low birthweight associated with prenatalcare and maternal risk status than women born inMexico. These results are consistent with previousfindings.",3 Factors associated with acculturation anddetailed medical, nutritional, and health profiles ofMexico-born versus US-born mothers need to bestudied in order to understand the reasons for thedifference observed in pregnancy outcomes in thesewomen. Prenatal care interventions designed for Mexi-can-American women should be sensitive to thedifferent cultural factors that are protective against poorpregnancy outcomes in these minority women.

Finally, it is noteworthy to point out that based on thelogistic regression analysis of determinants of lowbirthweight in Mexican Americans, an independenteffect was found for prenatal care utilization, maternalrisk status, maternal age, and maternal birthplace. Thisis the first report that was able to detect differences inthe risk of low birthweight in Mexican Americans

taking into account these factors and given the lowervariation in the low birthweight prevalences amongsome Mexican-American subgroups. Future studiesneed to clarify specific health, nutrition, and socialbehaviors as primary determinants of low birthweightin the Mexican-American population. Studies alsoshould investigate in more detail the determinants ofpreterm delivery and macrosomia in Mexican-American women.

Literature Cited1. Balcazar H, Aoyama C, Cai X. Interpretative views on

Hispanics' perinatal problems of low birth weight and prenatalcare. Public Health Rep. 1991;106:420-426.

2. Council on Scientific Affairs. Hispanic health in theUnited States. JAMA. 1991;265:248-252.

3. Mendoza F, Ventura S, Valdez B, Castillo R, Escoto L,Baisden K, et al. Selected measures of health status forMexican-American, mainland Puerto Rican, and Cuban-American children. JAMA. 1991;265:227-232.

4. Balcazar H, Cole G, Hartner J. Prenatal care utilization inMexican Americans and its relationship to maternal risk factorsand pregnancy outcome. Am J Prev Med. 1992;8:1-7.

5. Greenberg R. The impact of prenatal care in differentsocial groups. Am J Obstet Gynecol. 1983;1 45:797-801.

6. Leveno K, Cunningham G, Roark M, Nelson S, WilliamsL. Prenatal care and the low birth weight infant. Obstet Gynecol.1 985;66:599-605.

7. Alexander G, Cornely D. Prenatal care utilization: itsmeasurement and relationship to pregnancy outcome. Am JPrev Med. 1987;3:243-253.

8. David R. The quality and completeness of birthweightand gestational age data in computerized birth files. Am J PublicHealth. 1980;70:964-973.

9. Alexander G, Tompkins M, Cornely D. Gestational agereporting and preterm delivery. Public Health Rep.1990; 1 05:267-275.

10. Scribner R, Dwyer J. Acculturation and low birth weightamong Latinos in the Hispanic HANES. Am J Public Health.1989;79:1263-1267.


the effects of prenatal care utilization and maternal risk factors on

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