Maternal Physical Characteristics, Lifestyle Habits Predict Early Fetal Growth

From MedscapeCME Clinical Briefs

News Author: Laurie Barclay, MD
CME Author: Désirée Lie, MD, MSEd

CME Released: 02/18/2010; Valid for credit through 02/18/2011

February 18, 2010 — Maternal physical characteristics and lifestyle habits are independently associated with early fetal growth, according to the results of a study reported in the February 10 issue of the Journal of the American Medical Association.

"Adverse environmental exposures lead to developmental adaptations in fetal life," write Dennis O. Mook-Kanamori, MD, MSc, from Erasmus Medical Center in Rotterdam, the Netherlands, and colleagues. "The influences of maternal physical characteristics and lifestyle habits on first trimester fetal adaptations and the postnatal consequences are not known."

The goal of this study was to determine the risk factors and outcomes associated with first-trimester growth restriction. In Rotterdam, the Netherlands, between 2001 and 2005, a total of 1631 mothers with a known and reliable first day of their last menstrual period and a regular menstrual cycle were enrolled. The investigators evaluated associations of maternal physical characteristics and lifestyle habits with first-trimester fetal growth, and then subsequently looked at the associations of first-trimester fetal growth restriction with the risks for adverse birth outcomes and postnatal growth acceleration until age 2 years.

Between gestational ages of 10 weeks 0 days and 13 weeks 6 days, an ultrasound study was performed to measure first-trimester fetal growth based on crown-to-rump length. Primary study endpoints included preterm birth, defined as gestational age of less than 37 weeks; low birth weight (< 2500 g); and small size for gestational age (lowest fifth birth centile); as well as postnatal growth measured until age 2 years.

Maternal age was positively associated with first-trimester fetal crown-to-rump length, based on multivariate analysis (difference per maternal year of age, 0.79 mm; 95% confidence interval [CI], 0.41 -1.18 per SD score increase). Factors associated with a shorter crown-to-rump length were higher diastolic blood pressure and higher hematocrit level (differences, −0.40 mm; 95% CI, −0.74 to −0.06 and −0.52 mm; 95% CI, −0.90 to −0.14 per SD increase, respectively).

Shorter fetal crown-to-rump lengths were reported for mothers who both smoked and did not use folic acid supplements vs mothers who were nonsmokers and optimal users of folic acid supplements (difference, −3.84 mm; 95% CI, −5.71 to −1.98).

Compared with normal first-trimester fetal growth, adverse outcomes associated with first-trimester growth restriction included preterm birth (4.0% vs 7.2%; adjusted odds ratio [OR], 2.12; 95% CI, 1.24 - 3.61), low birth weight (3.5% vs 7.5%; adjusted OR, 2.42; 95% CI, 1.41 - 4.16), and small size for gestational age at birth (4.0% vs 10.6%; adjusted OR, 2.64; 95% CI, 1.64 - 4.25).

For each SD decrease in first-trimester fetal crown-to-rump length, there was a postnatal growth acceleration until age 2 years (SD score increase, 0.139 per 2 years; 95% CI, 0.097 - 0.181).

"Maternal physical characteristics and lifestyle habits were independently associated with early fetal growth," the study authors write. "First-trimester fetal growth restriction was associated with an increased risk of adverse birth outcomes and growth acceleration in early childhood....Further studies are needed to assess the associations of first-trimester growth variation on the risks of disease in later childhood and adulthood."

Limitations of this study include possible misclassification of gestational age because of inability to measure the timing of ovulation and implantation, and possible recall bias confounding dating of the last menstrual period.

In an accompanying editorial, Gordon C.S. Smith, MD, PhD, from the University of Cambridge in Cambridge, United Kingdom, notes that this study adds to the body of evidence suggesting that growth and placental function in the first trimester of pregnancy significantly affect fetal and infant growth.

"Hence, complications of late pregnancy may, at least for some women, already be determined in the first 3 months postconception, even before a woman has sought prenatal care," Dr. Smith writes. "The multiple associations described suggest that combined ultrasonic and biochemical screening in early pregnancy may be able to identify women at high risk of complications in late pregnancy. The challenges for future research are to produce robust screening tests with acceptable levels of detection and prediction, and to identify interventions that are effective in improving outcome when a pregnancy has been identified as high risk."

The first phase of the Generation R Study was supported financially by the Erasmus Medical Center, Rotterdam, the Erasmus University Rotterdam, and the Netherlands Organization for Health Research. One of the study authors (Dr. Jaddoe) has received funding from the Netherlands Organization for Health Research. The other study authors have disclosed no relevant financial relationships.

Dr. Smith reports that he has been a member of preterm labor advisory boards for GlaxoSmithKline. Funding for his editorial was provided by Cambridge National Institute for Health (NHS) Research Biomedical Research Centre, Cambridge University Hospitals, NHS Foundation Trust.

JAMA. 2010;303:527-534, 561-562. Abstract

Clinical Context

Human growth and development rates are highest in the first trimester of pregnancy, and first-trimester crown-to-rump length is used as a dating method in obstetrics and as an assessment of fetal growth. However, the relationship between fetal growth restriction in the first trimester and pregnancy and postnatal outcomes is still unknown.

This is a population-based, prospective cohort study to examine the association between maternal characteristics and lifestyle habits and first-trimester crown-to-rump length, and the association between growth restriction and neonatal and postnatal outcomes to 2 years.