Like Brother, Like Sister

Preemies younger sibling more likely to be underweight even in full term pregnancy

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Women who give birth early to their first child can expect their second child to be smaller than average at birth - even if the next child arrives on time.

Babies who are underweight for their gestational age are at higher risk for developmental problems, illness and death.

"Attend all OB/GYN prenatal visits while pregnant."

The results of a new study show that women who have previously given birth preterm are more likely to see their second child weighing in below the 10th percentile.

Lead author Jen Jen Chang, PhD, an epidemiology professor at the Saint Louis University School of Public Health, led the study, based on the Missouri state birth certificate records of 197,556 women who gave birth between the 20th and 44th week of pregnancy.

The women studied were under age 45 and were pregnant between 1989 and 2005. Chang and his colleagues looked only at women's first and second children's births.

A baby carried to full term was 71 percent more likely to be underweight if the baby's older sibling had been born before 28 weeks of pregnancy and 90 percent more likely if the sibling had been born between 29 and 32 weeks.

For babies born between 33 and 36 weeks, their younger siblings were 69 percent more likely to be under the 10th percentile in birthweight.

"Obstetricians should know that mothers who deliver prematurely are more likely to have smaller babies in the subsequent full term pregnancy," Chang said.

"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."

The researchers adjusted their findings to account for the time between the women's first and second pregnancy and the mother's age, race, weight before pregnancy, cigarette use and Medicaid status.

Chang's team also limited their study to pregnancies that did not have complications such as pre-eclampsia, diabetes, renal disease, high blood pressure, breach births or babies with birth defects.

The study did not address why the women's subsequent babies will more likely be smaller, but the information is still useful for doctors, said Dr. Kevin Gordon, M.D., an obstetrician and gynecologist from Arlington, Texas, who was not associated with the study.

"It will alert obstetricians to monitor growth more carefully," Gordon told dailyRx.

The study was presented February 9 at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in Dallas, TX. No information was available regarding the study's funding or financial disclosures of the authors.

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Last Updated:
February 16, 2012