Between 1997 and 1999, researchers at the University of Wisconsin-Madison conducted a pilot study to identify and assess why immigrant mothers (primarily those from Mexico) living in the United States have better pregnancy outcomes than native-born Hispanic mothers.

Key Findings: Despite being socially and economically disadvantaged, Mexican-American mothers have healthier babies (e.g., higher birth weight, less pre-maturity and fewer infant deaths) than do native-born Hispanic women. Health experts need more data in order to understand this "paradox."

Demographic and Economic Information:

• 87 percent of the women were born in Mexico. On average, they were 25.4 years old and had been living in the United States for seven years.
• Twenty-nine percent of the women had a high school or higher education.
• Eighty percent of the women were not employed. Monthly income was under $1,000 for 34 percent; $1,000–$2,000 for 38 percent; and more than $2,000 for 4 percent.
• 58 percent of the women were married and in a stable relationship and 27 percent were unmarried but living with a partner.

Behavioral Risk Factors:

• Few of the women smoked or consumed alcohol while they were pregnant, behaviors that are associated with poor birth outcomes. Seven respondents (2%) smoked and seven (2%) consumed alcohol while they were pregnant.

Pregnancy Outcomes:

• Few of the babies born were low birthweight, premature or in poor condition compared to other babies born in the United States.
  • The average birth weight was 3.607 kilos (compared to a national average of 3.393 kilos). Only 2 percent of infants were in the high-risk category (less than 2.5 kilos).
  • The average period of development for the infants was 39.6 weeks (less than 37 weeks results in premature babies).
  • The average Apgar score, which measures the newborn's skin color, heart rate, breathing, muscle tone and reflexes after birth, was 9.0; a score of 7–10 indicates the infant is in good to excellent condition.

Key Conclusions: The researchers concluded that the foreign-born Mexican-American mothers studied had better pregnancy outcomes than native-born Hispanic mothers because:

• They were more highly educated.
• They had better jobs, higher incomes and less teenage pregnancy.
• They were more integrated into the community and the United States.

They found no differences in outcomes related to "Americanization" (language use and duration of residency in the United States).

The Study: Researchers at the University of Wisconsin-Madison conducted this study in collaboration with the Alivio Medical Center in Chicago. The Alivio Medical Center provides broad medical services but focuses on prenatal care, women's health and pediatric care, primarily for Mexican-Americans.

The researchers developed the "Maternal and Child Health Among Mexican Immigrants in the U.S. Survey," completed when the women enrolled in the study, as the primary data collection tool. This survey covered demographic and economic information, the mother's health and pregnancy history, behavioral risk factors and more, and was available in Spanish and English.

They supplemented the survey results with information from:

• Prenatal clinic visit records.
• Delivery records.
• Clinic records on the health of mothers and the health and growth of their infants.
• Two follow-up interviews on the infants' health (the first a few weeks after the infant's birth and the second around his or her first birthday).

The researchers sub-contracted with the University of Wisconsin Survey Research Center for survey formatting, interviewer training and questionnaire testing, and with a student for translation of the survey into Spanish.

Some 450 female patients of the Alivio Medical Center who were pregnant or had recently had a baby completed the baseline survey and the first follow-up interview; 301 of these women also completed the second follow-up interview during the grant period.

Afterward: After the grant period, the researchers conducted the remaining follow-up interviews; final data analysis got underway in 2002.

They expanded the pilot study by following the women in the Robert Wood Johnson Foundation (RWJF)-funded phase for three years, and enlarging the sample to include their sisters living in Mexico (funded by the National Institute of Child Health and Human Development), and other Mexican mothers in Milwaukee and their sisters in Mexico.

Also, a University of Wisconsin graduate student is writing his doctoral dissertation on the results for the 150 women who completed the study after the end of the grant period.

The researchers plan to begin designing a comprehensive full-scale study of the pregnancy outcomes of Mexican immigrants living in the United States and their sisters in Mexico.