Preterm delivery (PTD) is a leading cause of infant death, and surviving infants are at risk for poor health. Data from the Iowa Health in Pregnancy Study, a case-control study of maternal stress on risk of PTD and small for gestational age (SGA) deliveries were used to address three aims: 1) develop a method to correct for error in ultrasound measurement among suspected SGA infants, 2) estimate the association of occupational stress on risk of PTD, and 3) examine injury-related risk factors for PTD.
Estimates of gestational age using ultrasound can be biased if the fetus is growth-restricted, yielding underestimates due to the small stature of the fetus. Multivariate linear regression modeling was used to estimate and correct for this bias among subjects with a suspected SGA infant who 1) began prenatal care in the first trimester, 2) reported a last menstrual period and 3) had an ultrasound examination between 7-21 weeks. To correct for this bias, an average of 1.5 weeks was added to the ultrasound gestational age. Following the correction, the proportion of PTD cases decreased from 29.1% to 26.5% while SGA cases increased from 23.7% to 31.3%.
Using this PTD classification, occupational physical and psychosocial stressors were studied. Continuous employment over the first 20 weeks of pregnancy was associated with a 30% increased risk of PTD versus not working. Working women reporting highly repetitive tasks (aOR=1.47(1.10-1.98)) or inadequate breaks (aOR=1.67(1.03-2.73)) were at increased risk of PTD. Working women who reported high lifting in the home had double the risk of PTD.
Over 5% of control subjects reported an injury during pregnancy, and injured women tended to be younger, unmarried, less educated, and have lower incomes. Women with injuries involving >1 body part (aOR=2.50(1.14-5.49)), or injuries to the abdomen and other regions of the body (OR=1.75(0.59-5.23)) were at increased risk of PTD.
Our findings provide a statistical approach to assess and correct for underestimates of ultrasound gestational age in case-control studies of PTD and SGA. The analyses of occupational exposures and injury during pregnancy indicate the need for studies that incorporate specific and standardized assessments of these exposures.
| Identifer | oai:union.ndltd.org:uiowa.edu/oai:ir.uiowa.edu:etd-1996 |
| Date | 01 December 2010 |
| Creators | Harland, Karisa Kay |
| Contributors | Saftlas, Audrey F. |
| Publisher | University of Iowa |
| Source Sets | University of Iowa |
| Language | English |
| Detected Language | English |
| Type | dissertation |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | Copyright 2010 Kari K. Harland |
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