PREVALENCE OF LOW-BIRTH-WEIGHT AND PRETERM DELIVERY IN RELATION TO THE INTERVAL BETWEEN PREGNANCIES AMONG WHITE AND BLACK-WOMEN

Background. The higher mortality rate among black infants than among w hite infants in the United States results largely from the greater fre quency of low birth weight and prematurity among black infants. Higher rates of low birth weight and preterm delivery have been associated w ith shorter intervals between pregnancies. Methods. We studied a racia lly mixed population of women in military families, who had access to free, high quality health care. A total of 1922 white and black women had two consecutive, singleton pregnancies during the study period. We determined the outcome of the second of each pair of pregnancies and the length of time between the pregnancies. Results. Short interpregna ncy intervals (calculated from delivery to the next conception) were m ore frequent among black than among white women. A total of 7.7 percen t of the 298 black women and 3.2 percent of the 1628 white women deliv ered premature, low-birth-weight infants (P < 0.001). Among the black women, an interpregnancy interval of less than nine months was associa ted with a significantly greater prevalence of preterm delivery and lo w birth weight in the neonates (11.6 percent, vs. 4.4 percent for long er interpregnancy intervals; P = 0.020). Among the white women, only i ntervals of less than three months between pregnancies were associated with a greater prevalence of prematurity and low birth weight in the infants (11.8 percent vs. 2.8 percent; P < 0.001). Of the black women, 46.3 percent had interpregnancy intervals of less than nine months; 4 .2 percent of the white women had interpregnancy intervals of less tha n three months. Conclusions. A short interval between pregnancies is a risk factor for low birth weight and preterm delivery, and such inter vals are more common among black than among white women. The relative frequency of intervals of less than nine months between pregnancies ma y be an important factor in the wide disparity in pregnancy outcomes b etween white and black women in the United States.