Low birthweight in Mexico: a systematic review.

There is abundant literature on the birth outcomes of women of Mexican origin living in the United States, but in most cases it does not refer to data available in Mexico. We conducted a systematic review of available data regarding low birthweight (LBW) rates in Mexico. We searched official online Mexican administrative data bases and four literature databases: OVID (Global Health), EMBASE, PubMed, and Bireme. The following inclusion criteria were used: (1) study is in English, Spanish, or Portuguese; (2) study presents data regarding LBW or birthweight distribution in Mexico; (3) study defines LBW as either < or ≤2,500 g; (4) study population includes newborn children; and, (5) LBW was a primary interest of the study. Because altitude influences birthweight, it was taken into account when comparing regions. Birth certificate data showed LBW rates of 8.2% in 2008 and 8.5% in 2009 among live births with known birthweights. In 2009, high altitude (≥2,000 m) federal entities (states and Mexico City) had LBW rates higher than the median (>7.9%). States at low altitudes (<50 m) had LBW rates lower than the median, with the exception of Yucatán state. The systematic literature review identified 22 hospital-based studies and three household interview surveys that met our inclusion criteria. The hospital-based LBW rates were relatively similar to the birth certificate data and slightly lower than survey data. Data on LBW rates are available in Mexico. They should be analyzed further and used for comparative studies.