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Objectives To evaluate the impact of Oportunidades, a large-scale, conditional cash transfer programme in Mexico, on birthweight. The programme provides cash transfers to low-income, rural households in Mexico, conditional on accepting nutritional supplements health education, and health care.
Methods The primary analyses used retrospective reports from 840 women in poor rural communities participating in an effectiveness study and randomly assigned to incorporation into the programme in 1998 or 1999 across seven Mexican states. Pregnant women in participating households received nutrition supplements and health care, and accepted cash transfers. Using multivariate and instrumental variable analyses, we estimated the impact of the programme on birthweight in grams and low birthweight (<2500 g), receipt of any pre-natal care, and number of pre-natal visits.
Results Oportunidades beneficiary status was associated with 127.3 g higher birthweight among participating women and a 4.6 percentage point reduction in low birthweight.
Conclusion The Oportunidades conditional cash transfer programme improved birthweight outcomes. This finding is relevant to countries implementing conditional cash transfer programmes.
Objectifs: Évaluer l’impact de Oportunidades, un programme de transfert conditionnel d’espèces sur une large échelle au Mexique sur le poids de naissance. Le programme permet un transfert d’argent vers les ménages ruraux à faibles revenus au Mexique à la condition de l’acceptation de suppléments nutritionnels, de l’éducation sur la santé et des soins de santé.
Méthodes: Les premières analyses ont utilisé des rapports rétrospectifs sur 840 femmes dans les communautés rurales pauvres participant à une étude d’efficacité et qui ont été intégrées de manière aléatoire au programme en 1998 ou en 1999 dans 7 États mexicains. Les femmes enceintes dans les ménages participants ont reçu des suppléments nutritionnels, des soins de santé et ont accepté des transferts de fonds. En utilisant des analyses multivariées et des variables instrumentales, nous avons estimé l’impact du programme sur les rapports maternels en poids de naissance en grammes et sur le faible poids de naissance (< 2500 g), la réception de toute sorte de soins prénataux et le nombre de visites prénatales.
Résultats: Le statut bénéficiaire d’Oportunidadesétait associéà 127,3 grammes de poids de naissance plus élevé chez les femmes participantes et à 4,6% de réduction du faible poids de naissance.
Conclusion: Le Programme Oportunidades de Transfert Conditionnel d’espèces a amélioré de poids de naissance. Cette constatation est importante pour les pays qui appliquent les programmes de transfert monétaire conditionnel en Amérique latine et ailleurs.
Objetivos: Evaluar el impacto sobre el peso al nacer de Oportunidades, un programa Mejicano a gran escala de transferencia monetaria condicionada. El programa provee una transferencia de dinero en metálico a hogares rurales, de bajos ingresos, en Méjico, con la condición de que acepten suplementos nutricionales, educación sanitaria y cuidados sanitarios.
Métodos: Los análisis primarios utilizaron reportes retrospectivos de 840 mujeres de comunidades rurales pobres que participaban en un estudio de efectividad y que fueron asignadas aleatoriamente a la incorporación del programa en 1998 o 1999 en 7 estados Mejicanos. Las mujeres embarazadas de hogares participantes recibieron suplementos nutricionales, cuidados sanitarios, y aceptaron la transferencia de dinero en metálico. Utilizando los análisis multivariado y de variable instrumental, estimamos el impacto del programa sobre reportes maternos del peso al nacer (en gramos) y bajo peso al nacer (<2500-gramos), el haber recibido cuidados prenatales y el número de visitas prenatales.
Resultados. El ser beneficiario del programa Oportunidades estaba asociado con un peso al nacer de 127.3 gramos más entre mujeres participantes y una reducción del 4.6% de bajo peso al nacer.
Conclusión. El programa de transferencia monetaria condicionada, Oportunidades, mejoró el peso al nacer. Este hallazgo es relevante para países que estén implementando programas de transferencia monetaria condicionada en Latinoamérica o cualquier otro lugar.
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Reducing the incidence of low birthweight is a global health priority because of its consequences on neonatal, childhood, and adolescent morbidity and mortality (Institute of Medicine 1985, McCormick 1985; Ashworth 1998; Moore et al. 1999), and adult economic productivity (Prentice & Moore 2005; Alderman & Berhman 2006). More than 95% of the 20 million low birthweight infants born globally per year come from low-income populations (UNICEF & WHO 2004). Whereas pre-term birth accounts for the majority of low birthweight infants in high-income settings (Blondel et al. 2002), intrauterine growth restriction (IUGR) and a combination of IUGR and pre-term births promotes low birthweight among many poor populations (de Onis et al. 1998). Low-income populations generally have a relatively high prevalence of infectious, nutritional, maternal, and perinatal conditions, which could include low nutritional intake and pre-pregnancy body mass index, hypertensive disorders of pregnancy and untreated infections (Villar & Belizan 1982; Bergström 2003; Kramer 2003).
Recommended interventions to reduce low birthweight in less developed settings include improving maternal nutrition and increasing the use of pre-natal care (Kramer 1987; Merialdi et al. 2003; Bhutta et al. 2005). Under controlled conditions, nutritional supplements have proven efficacious in promoting higher birthweight (Christian et al. 2003; Cogswell et al. 2003). For pre-natal care, however, randomized controlled trials comparing a standard number vs. reduced number of goal-oriented pre-natal visits report few significant improvements in birth outcomes (Villar et al. 2001). Reliable evidence of the effectiveness of these strategies is needed to guide investments that aim to improve infant and child survival.
In 1997, Mexico introduced a large-scale conditional cash transfer programme (CCT) that aims, in part, to improve birth outcomes through better maternal nutrition and use of pre-natal care. The programme (originally called PROGRESA and now Oportunidades), uses cash transfers as incentives for parents to invest in their children’s health and education so that they obtain the capabilities necessary to escape poverty when they reach adulthood. To improve reproductive health outcomes, Oportunidades’ cash transfers to beneficiary households are conditioned, in part, on pregnant women completing a prescribed pre-natal care plan, obtaining nutritional supplements, and attending an educational programme about health and nutritional topics.
Across diverse settings, CCTs have been successful in increasing the use of health services as well as reducing child mortality, mortality, anaemia, and stunting (Bautista et al. 2004; Gertler 2004; Gertler & Fernald 2004; Maluccio & Flores 2004; Morris et al. 2004; Rivera et al. 2004; Barham 2005; Rawlings & Rubio 2005). Previous health evaluations of CCTs have focused on child health outcomes and service utilization. In this article, we evaluate whether Mexico’s CCT programme had an impact on birthweight and pre-natal care utilization. Mexico is a good setting for this analysis as its CCT programme is the oldest and one of the largest programmes in existence. Despite efforts to reduce poverty and health disparities, Mexico’s poor are characterized by conditions amenable to health interventions, including high rates of nutrition and vitamin-related deficiencies (Hernandez-Diaz et al. 1999; Jaime-Perez & Gomez-Almaguer 2002; Shamah-Levy et al. 2003; Villalpando et al. 2003), infectious diseases (Sanchez-Perez et al. 2002; Brentlinger et al. 2003), and preventable morbidity and mortality related to reproductive health (Calderon-Garciduenas et al. 2002; Palacio-Mejia et al. 2003; Frank et al. 2004, CONAPO 2007).
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Table 1 compares the outcome variables, maternal and infant characteristics, and baseline household and community demographics and socioeconomics between non-beneficiary and beneficiary births. A total of 174 non-beneficiary and 666 beneficiary births were studied. The sampling strategy resulted in a well-balanced sample, as measured by only one significant difference at the 5% level for the 21 individual, household, and socioeconomic characteristics measured. Non-beneficiaries had more prior pregnancies (5.1) compared with 4.7 among beneficiaries.
Table 1. Comparison of individual, household and community characteristics for non-beneficiary and beneficiary births
|Variables||Mean (standard deviation)*||Difference||P-value|
|Maternal and infant characteristics†|
| Maternal age (years)||29.48 (6.38)||29.22 (6.75)||−0.25||0.66|
| Total prior pregnancies‡||5.05 ( 2.42)||4.62 (2.59)||−0.43||0.04|
| Prior miscarriage or abortion (%)||8.05||6.61||−1.44||0.49|
| Mother smoked during pregnancy (%)||4.60||4.80||0.20||0.89|
| Days after birth weighed||3.37 (7.81)||2.48 (6.08)||−0.89||0.12|
| Alive at time of interview (%)||99.43||98.20||−1.23||0.26|
| Female (%)||43.68||46.85||3.17||0.49|
|Baseline household socioeconomics and demographics|
| Household socioeconomic index (0–1)||0.42 (0.18)||0.41 (0.18)||−0.02||0.36|
| Indigenous-speaking household (%)||27.01||34.53||7.52||0.07|
| Educational level of household head (years)||3.70 (2.71)||3.60 (2.57)||−0.10||0.73|
| Age of household head (years)||41.32 (8.91)||40.17 (9.92)||0.15||0.15|
| Maternal educational level (years)||4.18 (2.54)||4.19 (2.73)||0.01||0.95|
| Household size||6.51 (2.23)||6.53 (2.43)||0.03||0.91|
| Males, 0–5 years in household (%)||0.15||0.14||−0.01||0.40|
| Females, 0–5 years in household (%)||0.16||0.14||−0.02||0.15|
| Males, 6–17 years in household (%)||0.14||0.16||0.02||0.22|
| Females, 6–17 years in household (%)||0.16||0.14||−0.01||0.25|
|Baseline community characteristics|
| Altitude (m)||1255.43 (855.58)||1333.69 (805.35)||78.26||0.34|
| Distance to urban centre (km)||106.42 (43.94)||107.91 (43.16)||1.49||0.75|
| Health centre in community (%)||78.13||81.23||3.10||0.32|
| Female wages, formal employment (pesos per month)||163.38 (507.28)||178.25 (576.46)||14.87||0.72|
| Male wages, formal employment (pesos per month)||221.10 (1218.51)||267.29 (1140.06)||46.19||0.42|
The first set of regressions evaluates programme impact on birthweight in grams and the odds of low birthweight (Table 2). In the unadjusted models, mean birthweight is 82 g higher for beneficiary births (P = 0.13). Including control variables that reduce residual variance, beneficiary status in the adjusted model predicts 127.3 g higher birthweight [95% confidence interval (CI): 21.3, 233.1; P = 0.02]. Separately, programme impact using the average beneficiary time on programme amounts to 68.3 g (P = 0.05), and programme impact from cash received amounts to 78.2 g (P ≤ 0.10). For low birthweight (Table 3), beneficiary status in the adjusted models predicts a 4.6 percentage point decrease in low birthweight and the average time on programme predicts a decline of 3.3 percentage points (P ≤ 0.05). The unadjusted model is not significant for low birthweight, but the coefficients are within the range of the CIs. We found no programme impact on pre-natal care-seeking, obtaining a minimum of five consultations, or the total number of consultations at conventional significance levels (Table 4).
Table 2. Programme impact on birthweight in grams*
|Programme participation, model||Programme impact||P-value|
|Beneficiary at birth, unadjusted model||81.98||0.13|
|Beneficiary at birth, adjusted model†||127.27||0.02|
|Programme months, adjusted model||68.26||0.05|
|Cash transfer, instrumental variable model||78.18||0.07|
Table 3. Programme impact on low birthweight*
|Programme participation variable, model†||Programme impact||P-value|
|Beneficiary at birth, unadjusted model||−0.031||0.18|
|Beneficiary at birth, adjusted model||−0.046||0.05|
|Programme months, adjusted model||−0.033||0.04|
|Cash transfer, instrumental variable model||−0.036||0.06|
Table 4. Programme impact on prenatal care utilization*
|Programme participation variable, model†||Got any prenatal care (=1)||Obtained five visits (=1)||Number of visits|
|Programme impact||P-value||Programme impact||P-value||Programme impact||P-value|
|Beneficiary at birth, unadjusted model||0.0274||0.08||0.0342||0.36||−0.2264||0.35|
|Beneficiary at birth, adjusted model||0.0250||0.12||0.0355||0.35||−0.2034||0.42|
|Programme months, adjusted model||0.0173||0.10||-0.0071||0.78||−0.1039||0.53|
|Cash transfer, instrumental variable model||0.0235||0.06||0.0235||0.42||−0.0022||0.99|
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We used retrospective reports from women who participated in a randomized effectiveness trial to examine the impact of Mexico’s CCT programme on birthweight among poor rural women. Overall programme impact amounts to a 127.3 g increase in birthweight and a 4.6 percentage point reduction in the incidence of low birthweight. The magnitude of the results compares well with previous impact evaluations of this programme. Prior studies reported that children in participating households have a 25.3% reduction in illness episodes and the probability of anaemia (Gertler 2004), and an increase in age-adjusted height by 1.1 cm (Rivera et al. 2004). These large effects could be attributed to intervention population, which is marginalized, poor (less than 20th wealth percentile nationally), and characterized by high rates of modifiable risk factors that could plausibly be addressed by increased use of quality healthcare.
We consider three possible pathways for this impact. Improved birthweight could have resulted from improved maternal nutrition, higher health care utilization, or improvements in the quality of health care received. Accepting nutritional supplements was a programme requirement for pregnant and lactating women, and these supplements were designed to meet their nutritional needs. Studies have noted, however, that there were major problems related to compliance, leakage, and availability at health centers of nutritional supplements for the Oportunidades programme (Adato et al. 2000). Zarco et al. 2006 reported that participants initially experienced nausea, diarrhea, and vomiting from the supplements, which probably affected compliance. Efforts to minimize such side effects by diluting the supplement may have reduced its nutrient density. Substantial leakage may have occurred due to a culture of sharing food (Adato et al. 2000). All of these factors could have reduced the desired health impact of the supplements. However, better nutrition could have also resulted from increases in disposal income. Participating households consumed on average 75 cents of every peso from the transfer programme, which left increased disposable income for investments (Gertler et al. 2004). Previous studies documented that beneficiary households used the additional financial resources for purchasing more and more nutritious calories (Hoddinott & Skoufias 2003). Higher levels of cash are associated with improved child anthropometric outcomes, possibly attributable to food purchases or improvements in household sanitation or environment (Fernald et al. 2008). Better nutrition or sanitation could be one pathway contributing to the results.
Improved birth outcomes could have also resulted from higher health care utilization. Specifically for pregnant women, five pre-natal visits are required, with an emphasis on monitoring the pregnancy’s progression; and the prevention, detection, and control of obstetric and perinatal risk factors. Bautista et al. 2004 reported that beneficiaries had higher rates of health service utilization; however, we found no differences in the odds of seeking pre-natal care or obtaining a higher number of consultations among women in this sample. It does not appear that the positive impact on birthweight, therefore, is attributable to increases in utilization resulting from the programme compliance requirements for pre-natal care.
Lastly, the programme impact on birthweight could have resulted from higher quality health care. The government had expressed an intention to increase supplies and human resources in anticipation of higher healthcare utilization in programme areas. However, a survey of 317 clinics conducted one year after programme implementation reported shortages of medical and support personnel, equipment, and drugs (Adato et al. 2000). At the same time, evidence suggests that beneficiaries did receive higher quality care (Barber & Gertler 2008). Given no evidence of supply-side improvements, this effect could be attributed to the programme’s goal of promoting more informed and active consumers of healthcare. Future research about Oportunidades will disaggregate these pathways to explain how the programme resulted in better health outcomes among children and adults.
This study has several limitations. It is limited to rural areas and initial years of programme implementation. In using birthweight outcomes, the study assumes that infants who experience intrauterine growth restriction are smaller at birth. However, birthweight does not always capture growth anomalies and large infants can be growth restricted (Wilcox 2001). Increasing birthweight is desirable if it leads to positive long-term health and developmental outcomes. Because of the prevalence of infectious, maternal, and perinatal conditions, it is plausible that health care and nutrition address the conditions that promote low birthweight in this setting. This contrasts with high-income populations characterized by increasing rates of pre-term birth related to the use of assisted reproduction technology and obstetrical interventions – for which pre-natal nutritional, medical, and risk assessment procedures have limited impact (Lu et al. 2003).
The study relies on the accuracy of maternal reports. Studies about maternal recall of birth characteristics consistently report correlations between maternal recall and medical records for birthweight and/or gestational age at approximately 0.9 (Lumey et al. 1994; Yawn et al. 1998; McCormick & Brooks-Gunn 1999; Tomeo et al. 1999; Walton et al. 2000; Buka et al. 2004; Catov et al. 2006). Among studies from low-income populations, the results are similar, and demonstrate that mothers can accurately recall perinatal events. Correlations between maternal recall of birthweight and medical records ranged from 0.89 to 0.95 in Taiwan (Sou et al. 2006) and 0.89 to 0.96 in Israel (Gofin et al. 2000). Researchers in the Philippines reported specificity correlations of 0.8 to 0.9 for obstetrical complications reported by mothers and hospital records (Stewart & Festin 1995). Robles and Goldman (1999) compared birthweight data from health interview surveys with weighted estimates derived from delivery characteristics and maternal education. They conclude that survey data could underestimate the true incidence of low birthweight in a given country, and that most studies lack an objective standard of comparison. We are unaware of studies that have been conducted among the poor in rural Mexico about the accuracy of birthweight recall. However, this survey was designed by the Population Council in Mexico; in addition, household surveys such as the Demographic and Health Surveys conducted in low-income settings routinely use maternal reports.
The time interval is a factor in maternal recall, and there was a difference in the median time since birth between the groups in this study. We evaluated the presence of recall bias empirically with the data. Specifically, we estimated regression models for birthweight in grams for beneficiaries and non-beneficiaries with the explanatory variables as a set of dummy variables for child year of birth. We found no significant results for the year dummies, suggesting that time since birth did not affect recall bias in this study.
Women that reported birthweight in grams are associated with a higher number of household assets and maternal age. However, beneficiary status and time on the programme are not associated with the availability of birthweight data. As confirmed by the descriptive comparisons, missing birthweight observations do not affect the balance of characteristics between beneficiaries and non-beneficiaries for this sample.