Study confirms recurrence of small-for-gestational-age pregnancies

In a study to be presented on February 16 at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in San Francisco, researchers will report findings that suggest women whose babies are small-for-gestational-age (SGA) in their first pregnancy have a strongly increased risk for SGA in a second pregnancy.

The aim of this study was to assess and describe in detail the incidence of SGA infants and the SGA recurrence rate in general. Additionally, it sought to assess the incidence and recurrence rate of SGA in women with and without a hypertensive disorder in their first pregnancy.

Infants who are small for gestational age (birth weight below the fifth percentile) are a heterogeneous group comprised of infants that have failed to achieve their growth potential (fetal growth restriction; FGR) and infants who are constitutionally small. SGA infants are at increased risk for perinatal mortality and adverse perinatal and health outcomes later in life.

"The main strength of this study was the size and composition of the cohort," said B J Voskamp, MD. "Data were derived from a large, well-maintained, population-based national perinatal registry."

The study was performed in a prospective nationwide cohort with the use of the Netherlands Perinatal Registry (PRN). The PRN consists of population-based data that includes information on pregnancy and delivery of 96 percent of pregnancies in the Netherlands. From this, they studied a cohort of women who delivered two subsequent singleton pregnancies (first and second deliveries) in the Netherlands from Jan. 1, 1999, through Dec. 31, 2007.

The primary outcome measure was SGA. Researchers registered demographic and obstetric characteristics including maternal age, parity, ethnicity, and socioeconomic status (SES).

Cases were analyzed in total and stratified into two groups: women with and without a hypertensive disorder in their first pregnancy. The analysis was stratified by gestational age at delivery in the first pregnancy in 3 groups: very preterm, late preterm, and full-term.

After exclusions, the study population was comprised of 259,481 women (518,962 deliveries). Five percent (12,943) of the women gave birth to SGA infants in their first pregnancy, and of those same women, SGA recurred in 2996 women (23.2 percent) in the subsequent pregnancy. SGA in the second pregnancy in women who had not previously had an SGA baby occurred in 3.4 percent of the women.

Further, the risk of SGA recurrence in women with hypertensive disorder in their first pregnancy was smaller than in women who did not. However, the risk of "de novo" SGA in the second pregnancy was higher for those with hypertensive disorder than their counterparts.