Short and long IPI after live birth, but not after pregnancy termination, showed increased odds for PTB.

Objective To investigate the distribution of known factors for preterm birth (PTB) by severity of maternal underweight; to investigate the risk adjusted relationship between severity of underweight and PTB and to assess if the relationship differed by gestational age. Design Retrospective cohort study. Setting State of California, USA. Methods Maternally linked hospital and birth certificate records of 950,356 California deliveries in 2007–2010 were analyzed. Singleton live births of women whose pre-pregnancy body mass index (BMI) was underweight (<18.5 kg/m2) or normal (18.50–24.99 kg/m2) were analyzed. Underweight BMI was further categorized as: severe (<16.00), moderate (16.00–16.99) or mild (17.00–18.49). PTB was grouped as 22–27, 28–31, 32–36 or <37 weeks (compared with 37–41 weeks). Adjusted multivariable Poisson regression modeling was used to estimate relative risk for PTB. Main outcome measures Risk of PTB. Results 72,686 (7.6%) women were underweight. Increasing severity of underweight was associated with increasing percent PTB: 7.8% (n=4421) in mild, 9.0% (n=1001) in moderate and 10.2% (475) in severe underweight. The adjusted relative risk of PTB also significantly increased: aRR=1.22 (95%CI: 1.19–1.26) in mild, aRR=1.41 (95%CI: 1.32–1.50) in moderate and aRR=1.61 (95%CI: 1.47–1.76) in severe underweight. These findings were similar in spontaneous PTB, medically indicated PTB, and the gestational age groupings. Conclusion Increasing severity of maternal pre-pregnancy underweight BMI was associated with increasing risk adjusted PTB at <37 weeks. This increasing risk was of similar magnitude in spontaneous and medically indicated births and in preterm delivery at 28–31 and at 32–36 weeks of gestation.

No abstract

Mexico achieved independence in 1821. With the definitive cutting of the imperial ties with Spain, already weakened by the impact of the Napoleonic Wars, the country began to play an individual role in the world economy. The end of Spanish rule and the departure of many Spaniards opened up new positions and new opportunities for Mexicans. Some they seized immediately as in government and the army; others they lacked in some measure the skills, inclination or capital to exploit. One of the more difficult areas was overseas trade, which had been largely the preserve of peninsulares. Their departure provided the occasion for the arrival of numbers of foreigners, who established merchant houses in trading centres, and assumed the role of middlemen in Mexico's foreign trade.

By 1820, much of Spanish South America had achieved independence, and Spain was on the defensive in those areas where her flag still flew. Amongst the countries that gained their independence in this period was Chile, which after the battle of Maipú in April 1818, faced no further threats to its existence from Spain. For many of the new nations, the period immediately after independence was one of political instability, shading into civil war, and Chile was no exception. However, in comparison with many of its neighbors, the period of instability was short, and the physical destruction not great.