Study finds prior preterm delivery indicates subsequent baby will be small even if carried to term

In a study to be presented today at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in Dallas, Texas, researchers will report findings that indicate that women who deliver their first baby early are more likely to have a subsequent baby that is small for its gestational age, even when the second pregnancy is carried to term.

While there is much research that shows mothers who deliver their first babies early are more likely to have subsequent babies early, this study, Prior Preterm Birth in First Pregnancy and Risk of Small-for-Gestational-Age Birth in Second Pregnancy: A Population-Based Study, sought to determine whether mothers whose first babies are delivered early are more likely to have second babies that are small for their gestational age when the second pregnancy is carried to term. This is a significant public health issue because smaller babies tend to have more developmental problems and be sick more often, and are more likely to die.

"Obstetricians should know that mothers who deliver prematurely are more likely to have smaller babies in the subsequent full term pregnancy," said Jen Jen Chang, Ph.D., assistant professor at the department of epidemiology at the Saint Louis University School of Public Health and the study's lead author. "They should closely monitor fetal weight and fetal growth in mothers who have delivered early, even if the mothers are receiving treatments to prevent them from giving birth prematurely again."

Chang and his colleagues looked at the Missouri state birth certificate records of 197,556 women who were pregnant between 1989 and 2005. They included women younger than 45 who gave birth between 20 and 44 weeks of gestation. These women had "normal" pregnancies that were without medical complications such as hypertension, preeclampsia, diabetes or renal disease. The resulting babies were not breach births and did not have birth defects.

The findings indicate that if a mother delivered her first baby prematurely her second one is more likely to be small for gestational age, even if that baby arrived at the normal time (between 37 and 44 weeks of gestation) and the pregnancy was normal and uncomplicated.

In addition to Chang, the study was conducted by Lung-Chang Chien, Washington University in St. Louis, Siteman Cancer Center, St. Louis, Mo.; and George Macones, Washington University in St. Louis, Department of Obstetrics and Gynecology, St. Louis, Mo.