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First-trimester growth and the risk of low birth weight
G C Smith1, M F Smith, M B McNay
1Department of Physiology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Insights
Suboptimal first-trimester growth, measured by crown-rump length, is linked to an increased risk of low birth weight and premature delivery. This finding highlights the importance of early fetal development for birth outcomes.
Area of Science:
- Obstetrics and Gynecology
- Fetal Development
- Perinatal Medicine
Background:
- Established correlation between first-trimester size and birth weight.
- Uncertainty regarding the link between first-trimester growth and low birth weight.
- Need to investigate the relationship between early embryonic/fetal size and low birth weight for gestational age.
Purpose of the Study:
- To determine if first-trimester embryo/fetus size predicts the risk of low birth weight.
- To assess the association between first-trimester growth and birth weight that is low for gestational age.
Main Methods:
- Analysis of ultrasound records from over 30,000 pregnancies.
- Inclusion of 4,229 pregnancies with normal maternal history and first-trimester crown-rump length (CRL) measurements.
- Examination of the relationship between CRL deviation (in equivalent days of growth) and pregnancy outcomes.
Main Results:
- A first-trimester CRL 2-6 days smaller than expected increased the risk of birth weight <2500g (RR 1.8).
- Smaller CRL was associated with higher risk of birth weight <5th percentile for gestational age (RR 3.0) and preterm delivery (24-32 weeks, RR 2.1).
- No significant association found with delivery between 33-36 weeks.
Conclusions:
- Suboptimal first-trimester growth is a potential risk factor for low birth weight.
- Early growth restriction may predict low birth weight percentile and premature delivery.
- First-trimester ultrasound measurements can offer insights into potential adverse birth outcomes.
Background:
Previous studies have demonstrated a correlation between first-trimester size and birth weight. It is not known, however, whether low birth weight is related to first-trimester growth. We sought to determine whether the risk of low birth weight and birth weight that was low for gestational age is related to the size of the embryo or the fetus in the first trimester.
Methods:
From a data base of ultrasound records of more than 30,000 pregnancies, we identified women who had no important medical problems, a normal menstrual history, and a first-trimester ultrasound scan in which the crown-rump length of the embryo or fetus had been measured. We examined the relation between the outcome of 4229 pregnancies and the difference between the measured and the expected crown-rump length in the first trimester, expressed as equivalent days of growth.
Results:
A first-trimester crown-rump length that was two to six days smaller than expected was associated with an increased risk (as compared with a normal or slightly larger than expected crown-rump length) of a birth weight below 2500 g (relative risk, 1.8; 95 percent confidence interval, 1.3 to 2.4), a birth weight below 2500 g at term (relative risk, 2.3; 95 percent confidence interval, 1.4 to 3.8), a birth weight below the fifth percentile for gestational age (relative risk, 3.0; 95 percent confidence interval, 2.0 to 4.4), and delivery between 24 and 32 weeks of gestation (relative risk, 2.1; 95 percent confidence interval, 1.1 to 4.0), but not with delivery between 33 and 36 weeks (relative risk, 1.0; 95 percent confidence interval, 0.7 to 1.5).
Conclusions:
Suboptimal first-trimester growth may be associated with low birth weight, low birth-weight percentile, and premature delivery.