No abstract

Abstract-The role of report/recall bias in case-control studies of low birth weight (LBW) was investigated in women who gave birth at a tertiary hospital. Prenatal exposure information reported at the postpartum interview was compared with that documented during pregnancy in obstetric records. 169 cases of LBW and 198 controls were selected. The two sets of information on case mothers and control mothers were compared, using the medical record as a reference. Kappa values were estimated. No trend was observed to increase/decrease the sensitivity and specificity of recall. Agreement on alcohol use was very low (kappa = 0.11 for case mothers and 0.03 for control mothers): on obstetrical records, only 12 mothers of cases reported habitual alcohol intake at the first prenatal care visit, whereas in the interview 69 said yes to the same question; in control mothers, the figures were 4 and 89 respectively. Odds ratios (ORs) of exposure estimated from the two sets of data did not differ importantly in 8 variables. Interview data yielded ORs for hypertension (8.39 versus 4.63), anemia (0.44 versus 0.99) that were farther from the null, and ORs in the opposite direction for alcohol (0.83 versus 1.61) and any drug (0.64 versus 1.42). In conclusion, given that OR figures are similar for most variables and no trend is observed in sensitivity/specificity, mothers of normal births can be an adequate reference group, using personal interviews to obtain information on lifestyle, and medical records for conditions.

In a case-control study, we compared the ability of two indices of antenatal care use, the new Adequacy of Prenatal Care Utilization (APNCU) index and the Kessner index, to predict low birthweight. In crude analyses, both indices showed a linear trend with low birthweight. After controlling for confounding, however, the APNCU index was unrelated to low birthweight. To learn whether the Kessner index added explanatory information to the APNCU index (or vice versa), we regressed the APNCU index on the Kessner index (and vice versa) and computed residuals for both indices. In logistic regression analyses, the residuals of the Kessner index added meaningful information to the APNCU index, whereas the opposite did not occur.

The main objective of this study is to examine the effect of several variables, including altitude of maternal residence, on delivering a low birth weight (LBW) newborn. A case-control study was done. Two hundred forty cases (single newborn weighing less than 2,500 g) and 374 controls (single newborn weighing more than 2,499 g) were included. Information was gathered from the clinical chart of delivering women, through a personal interview and the Spanish Census Bureau (for altitude). Predictors of LBW were assessed through stepwise logistic regression analysis. Several well-known LBW risk factors were identified: hypertension, weight gain during pregnancy, body size (mainly maternal prepregnancy weight), low social class, primiparity, and several conditions (spontaneous delivery, abruptio placentae). Altitude was an independent predictor of LBW at term (more than 37 weeks of gestational age) but not for preterm LBW. Nevertheless, a relationship between altitude and birth weight was not found in controls, although a moderate decreasing gradient with altitude was observed. The limitations of these findings are discussed.

The value of prenatal care is controversial and difficult to establish. A national policy for improving perinatal outcomes was proposed and applied throughout Andalusia (Southern Spain) in 1984. Here we report the results of an evaluation of this health care program as regards the prevention of preterm delivery. Effectiveness of prenatal care was assessed on the basis of two case-control studies in a hospital setting: one performed before the program was implemented (1981-1982) and the second one six years after the program began (1990-1993). A total of 229 cases and 395 controls for the period 1981-1982, and 207 cases and 381 controls for 1990-1993 were selected. Prenatal care was assessed based on the number of prenatal care visits, the date of the first visit, and an American composite index adjusting for gestational age. Multiple-factor adjusted odds ratios and their 95% confidence intervals (CI) were estimated using unconditional logistic regression analysis. The use of prenatal care significantly improved across time: the proportion of women receiving no prenatal care decreased from over 30% to less than 5%, and the proportion of women starting prenatal care in the first trimester for 1990-1993 was three times greater than the figure for 1981-1982. In the 1981-1982 case-control study, the date of first visit and the composite index were shown to be unrelated to preterm birth risk; and the number of visits yielded a significant association, although no definite trend could be established. In the 1990-1993 case-control study, a clear and significant relationship was observed between the number of prenatal care visits, the trimester of the first visit, and the adequacy of care according to the composite index. This latter variable, reflecting a more stringent standard of prenatal care, was selected by a stepwise logistic regression analysis as the best predictor for preterm birth risk. The results suggest that the present Andalusian program helps prevent preterm delivery. Nonetheless, its minimum standards should be raised to further decrease preterm birth risk.