The Relationship Between Recurrent Placental Pathology and Recurrent Poor Pregnancy Outcome

Abstract

Poor pregnancy outcome (PPO) is a top agenda item in health and political arenas. Most prominent PPOs are low birth weight (LBW) and preterm delivery (PTD). Effective interventions to maximize pregnancy outcome will diminish their negative impact. The placenta is a diary of the infant's prenatal experiences. Changes in the placenta provide clues to the uterine environment during the pregnancy. Each placental pathology represents a different insult, including severity, duration and type.

The Collaborative Perinatal Project of the National Institute of Neurological and Communicative Disorders and Stroke was a longitudinal study of obstetric outcomes in women. The study was conducted from 1959 to 1966 and contains information for 53,518 pregnancies from 10,699 women, including examination of 31,494 placentas (59%). A nested case control study was conducted on this dataset. A sample of 7653 women of black and white races who had two pregnancies during the study period were examined to determine if a relationship existed between the recurrence of PPO and a recurrence of placental pathology.

Analysis used several statistical techniques including linear logistic regression and an experimental causal modelling program, TETRAD II. TETRAD II analysis indicated a relationship between marital status and educational incongruity and PPO along with a relationship between recurrent chronic hypoxia and LBW and recurrent infection and PTD. This was the first time TETRAD II was used on real data.

Linear logistic regression confirmed these relationships. The risk of repeating LBW or PTD was 1.6 times greater if the woman was unmarried and was 10% greater for each year of greater educational incongruity between the mother and father of the baby. Cigarette smoking in both pregnancies represented 2.1 (1.5-2.9) times greater risk of repeating LBW. There was a 4.2 (1.4-12) times greater risk of repeating PTD if placental chorionic villitis repeated, remaining significant after adjustment for cigarette smoking and social class. There was a 6.5 (1.4-31) times greater risk of repeating LBW if decidual necrosis repeated, remaining significant after adjustment for social class, but becoming marginal when cigarette smoking was included. The main implication of these findings involves the area of preconceptual care for women. This includes preconceptual treatment of infection and nursing support to women at high risk for repeating a PPO.