Rates of and factors associated with recurrence of preterm delivery.

CONTEXT: Information about risk of recurrent preterm delivery is useful to clinicians, researchers, and policy makers for counseling, generating etiologic leads, and measuring the related public health burden. OBJECTIVES: To identify the rate of recurrence of preterm delivery in second pregnancies, factors associated with recurrence, and the percentage of preterm deliveries in women with a history of preterm delivery. DESIGN AND SETTING: Population-based cohort study of data from birth and fetal death certificates from the state of Georgia between 1980 and 1995. SUBJECTS: A total of 122 722 white and 56174 black women with first and second singleton deliveries at 20 to 44 weeks' gestation. MAIN OUTCOME MEASURE: Length of gestation (categorized as 20-31, 32-36, or > or =37 weeks) at second delivery compared with length of gestation at first delivery, by age and race. RESULTS: Most women whose first delivery was preterm subsequently had term deliveries. Of 1023 white women whose first delivery occurred at 20 to 31 weeks, 8.2% (95% confidence interval [CI], 6.6%-10.1%) delivered their second birth at 20 to 31 weeks and 20.1% (95% CI, 17.7%-22.8%) at 32 to 36 weeks. Of 1084 comparable black women, 13.4% (95 % CI, 11.4%-15.6%) delivered at 20 to 31 weeks and 23.4% (95% CI, 20.9%-26.1%) delivered at 32 to 36 weeks. Among women whose first delivery occurred at 32 to 36 weeks, all corresponding rates were lower than those whose first birth was at 20 to 31 weeks; the rates of second birth at 20 to 31 weeks were substantially lower (for white women, 1.9% [95% CI, 1.7%-2.2%]; for black women, 3.8% [95% CI, 3.4%-4.2%]). Compared with women aged 20 to 49 years at their second delivery, women younger than 18 years had twice the risk of recurrence of delivery at 20 to 31 weeks. Of all second deliveries at 20 to 31 weeks, 29.4% for white women and 37.8% for black women were preceded by a preterm delivery. CONCLUSIONS: Our data suggest that recurrence of preterm delivery contributes a notable portion of all preterm deliveries, especially at the shortest gestations.

Racial differences in the patterns of singleton preterm delivery in the 1988 National Maternal and Infant Health Survey.

OBJECTIVES: To determine if the association between race and preterm delivery would persist when preterm delivery was partitioned into two etiologic pathways. METHODS: We evaluated perinatal and obstetrical data from the 1988 National Maternal and Infant Health Survey and classified preterm delivery as spontaneous or medically indicated. Discrete proportional hazard models were fit to assess the risk of preterm delivery for Black women compared with White women adjusting for potential demographic and behavioral confounding variables. RESULTS: Preterm delivery occurred among 17.4% of Black births and 6.7% of White births with a Black versus White unadjusted hazard ratio (HR) of 2.8 (95% CI = 2.4-3.3). The adjusted HR for a medically indicated preterm delivery showed no racial difference in risk (HR = 1.0, 95% CI = 0.4-2.6). However, for spontaneous preterm delivery between 20 and 28 weeks gestation, the Black versus White adjusted hazard ratio (HR) was 4.9 (95% CI = 3.4-7.1). CONCLUSIONS: Although we found an increased unadjusted HR for preterm delivery among Black women compared with White women, the nearly fivefold increase in adjusted HR for the extremely preterm births and the absence of a difference for medically indicated preterm delivery was unexpected. Given the differences in the risks of preterm birth between Black and White women, we recommend to continue examining risk factors for preterm delivery after separating spontaneous from medically indicated preterm birth and subdividing preterm delivery by gestational age to shed light on the reasons for the racial disparity.

Patterns of prenatal care initiation in Georgia, 1980-1992.

OBJECTIVE: To determine whether characteristics in a woman's first pregnancy were associated with the trimester in which she initiated prenatal care in her second pregnancy. METHODS: Data for white and black women whose first and second pregnancies resulted in singleton live births between 1980 and 1992 were obtained from Georgia birth certificates (n = 177,041). Adjusted relative risks (RRs) for early prenatal care in the second pregnancy were computed by logistic regression models that included trimester of prenatal care initiation, infant outcomes, or maternal conditions in the woman's first pregnancy as the exposure and controlled for maternal age, education, child's year of birth, interval between first and second pregnancy, presence of father's name on the birth certificate, and the interaction between prenatal care and education. Models were stratified by race. RESULTS: Women of both races who initiated prenatal care in the first trimester of their first pregnancies were more likely than those with delayed care to initiate prenatal care in the first trimester of their second pregnancies (RR = 1.25 and 1.63 for white and black women educated beyond high school, respectively). Both white and black women who delivered a baby with very low birth weight (RR = 1.06 and 1.15, respectively) or who suffered an infant death (RR = 1.09 and 1.31, respectively) in their first pregnancies were more likely than those who did not experience these events to begin prenatal care in the first trimester of their second pregnancies. CONCLUSION: Women with some potentially preventable adverse infant outcomes tend to obtain earlier care in their next pregnancy. Unfortunately, women who delayed prenatal care in their first pregnancy frequently delay prenatal care in their next.

Trends in the percentage of women who received no prenatal care in the United States, 1980-1992: contributions of the demographic and risk effects.

OBJECTIVE: To determine if the increase in the percentage of women who received no prenatal care in the United States relative to 1980 (from 1.3% in 1980 to 2.2% in 1989 and 1.7% in 1992) was due to increasing risks of no care in subgroups of women or increasing percentages of births to women at high demographic risk of no care. METHODS: We analyzed U.S. birth certificates for the period 1980-1992. The annual adjusted odds of no prenatal care relative to 1980 were computed by logistic regression models that included year, maternal characteristics, and interactions of these characteristics with year. We also examined changes in the annual distributions of births by maternal characteristics. RESULTS: The risk of no prenatal care in most subgroups increased during the early 1980s, peaked in the late 1980s, and declined thereafter. For example, among black women, the adjusted risk of no care more than doubled from 1980 to 1989. Throughout the 1980s and into the 1990s, the percentage of births to women at high demographic risk of no care increased. This increase in the percentage of births to women at high demographic risk shows no sign of abating. CONCLUSIONS: During the 1980s, increasing risks in subgroups of women drove the increase in the crude rate of no prenatal care. Despite decreases in the risks of no care in the early 1990s, increasing percentages of births to women with high demographic risk for no care prevented a decrease in the crude rate to the 1980 level.

Heterogeneity between women who received prenatal care in the third trimester and those who received no prenatal care.

OBJECTIVE: To determine whether women who received prenatal care in the third trimester differed from those who received no prenatal care. METHODS: We analyzed US birth certificates from 1990 through 1992, computing the distribution of live births for women who received prenatal care in the third trimester and for those who received no prenatal care according to eight demographic and pregnancy-related characteristics (age, race, marital status, residence, country of birth, education, interbirth interval, and parity). We used the Cochran-Mantel-Haenszel statistic to test the significance of the differences between the distributions for each characteristic, adjusting simultaneously for the other seven characteristics. RESULTS: Women who received no prenatal care differed from women who received prenatal care in the third trimester for each of the demographic and pregnancy-related characteristics we examined. Among black and unmarried women, the two categories of prenatal care differed by more than 10%. CONCLUSIONS: The characteristics of women who received no prenatal care and those of women who received prenatal care in the third trimester were heterogeneous. Strategies to promote earlier prenatal care should be specific and sensitive to women at risk for each category of late entry to prenatal care.