Major Finding: Fetuses in the lowest 20% of crown-to-rump length had a 7% risk of preterm birth, an 11% risk of small size for gestational age, and an 8% risk of low birth weight. These rates were 4%, 4%, and 3.5%, respectively, among fetuses without growth restriction.
Data Source: A population-based prospective study of 1,631 pregnant women.
Disclosures: Dr. Mook-Kanamori reported no relevant conflicts of interest. Dr. Smith reported being a member of GlaxoSmith-Kline's preterm labor advisory boards.
Pregnant women who smoke, don't take folic acid supplements, or have higher than average blood pressure or hematocrit levels are at greater risk than others for fetal growth restriction during the first trimester.
In turn, such growth restriction is associated with a greater risk of poor outcomes such as preterm birth, small size for gestational age (SGA) at birth, and a compensatory accelerated rate of postnatal growth that persists until age 2 years, said Dr. Dennis O. Mook-Kanamori and his associates at Erasmus Medical Center, Rotterdam, the Netherlands.
These findings from a population-based prospective study involving 1,631 pregnant women suggest that growth patterns as early as the first trimester have a far-reaching influence, perhaps affecting disease risk in adulthood as well as in childhood, the investigators said.
They assessed fetal crown-to-rump length via ultrasound during the first trimester among women participating in a larger study in the Netherlands.
Higher than average diastolic blood pressure and hematocrit levels, smoking, and nonuse of folic acid supplements significantly correlated with shorter crown-to-rump length. There was even a dose-response relation between the number of cigarettes smoked and the degree of growth restriction.
Maternal weight and height showed no relation to the development of fetal growth restriction.
Fetuses in the lowest 20% of crown-to-rump length had a 7% risk of preterm birth, an 11% risk of SGA, and an 8% risk of low birth weight (LBW). In contrast, these rates were 4%, 4%, and 3.5%, respectively, among fetuses that did not show growth restriction.
This indicates a two- to threefold increase in risk for these complications, Dr. Mook-Kanamori and his colleagues said (JAMA 2010;303:527–34).
First-trimester fetal crown-to-rump length also correlated with head circumference, femur length, and weight not only throughout pregnancy and at birth, but also at 1-year and 14-month assessments. This correlation had disappeared by the time the study subjects were evaluated at age 2 years.
“Increased postnatal growth rate is a well-established risk factor for metabolic and cardiovascular disease in later life,” the researchers noted.
In an editorial, Dr. Gordon C.S. Smith of the University of Cambridge (England) said these findings suggest that “complications of late pregnancy may, at least for some women, already be determined in the first 3 months post conception, even before a woman has sought prenatal care” (JAMA 2010;303:561–2).