Maternal urine albumin excretion and pregnancy outcome.
BACKGROUND
Vascular dysfunction has been hypothesized as a causal pathway for preeclampsia, impaired fetal growth, and early parturition. The relationship between increased urine albumin excretion (albuminuria), a marker of endothelial dysfunction, and preterm birth has not been fully evaluated.


METHODS
We conducted a nested case-control study of 404 pregnancies from 1998 to 2000 within the Pregnancy, Infection and Nutrition cohort. Cases consisting of live births delivered before 37 weeks of gestation (preterm birth, n = 111) were compared with term births from the same cohort (n = 293). Albumin-creatinine ratio (in milligrams per gram) was measured in urine collected around 27 weeks of gestation. We compared risks for preterm birth in mothers with albuminuria with albumin levels of 3 to 20 mg/g and greater than 20 mg/g relative to those with albumin levels less than 3 mg/g by using logistic regression.


RESULTS
Median albuminuria was albumin level of 2.7 and 4.3 mg/g for term and preterm births, respectively. Albuminuria was strongly associated with preterm birth in a dose-response fashion, with adjusted odds ratios of 1.9 (95% confidence interval, 1.1 to 3.1) and 4.7 (95% confidence interval, 1.7 to 12.6) for albuminuria with albumin of 3 to 20 mg/g and greater than 20 mg/g, respectively. The association was present for both spontaneous and medically induced preterm births, but the effect was decreased and the dose-response relationship was eliminated by excluding high-risk groups and those with pregnancy complications.


CONCLUSIONS
Low levels of albuminuria are associated with preterm birth. The mechanism underlying this association warrants additional exploration.
Franceschini
Nora
N
Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, NC 27599-7155, USA. noraf@med.unc.edu
Savitz
David A
DA
Kaufman
Jay S
JS
Thorp
John M
JM
D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D000419:Albuminuria / Q000453:epidemiology*; D016022:Case-Control Studies; D015331:Cohort Studies; D004730:Endothelium, Vascular / Q000503:physiopathology; D005260:Female; D006801:Humans; D006973:Hypertension / Q000453:epidemiology; D046110:Hypertension, Pregnancy-Induced / Q000453:epidemiology; D007231:Infant, Newborn; D007234:Infant, Premature; D007751:Labor, Induced / Q000706:statistics & numerical data; D009657:North Carolina / Q000453:epidemiology; D009765:Obesity / Q000453:epidemiology; D007752:Obstetric Labor, Premature / Q000453:epidemiology; D011225:Pre-Eclampsia / Q000453:epidemiology; D011237:Predictive Value of Tests; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D011256:Pregnancy Outcome; D011263:Pregnancy Trimester, Third; D012907:Smoking / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data