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Effects of symmetric and asymmetric fetal growth on pregnancy outcomes
J S Dashe1, D D McIntire, M J Lucas
1Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center at Dallas, 75390-9032, USA. jodi.dashe@email.swmed.edu
Insights
Head circumference to abdomen circumference (HC/AC) asymmetry in small for gestational age (SGA) fetuses indicates a higher risk of adverse pregnancy outcomes and neonatal complications. Symmetric SGA infants did not show increased risks compared to appropriate for gestational age (AGA) infants.
Area of Science:
- Perinatology
- Fetal Medicine
- Neonatology
Background:
- Small for gestational age (SGA) infants represent a significant proportion of high-risk neonates.
- Head circumference to abdomen circumference (HC/AC) ratio is a key indicator of fetal growth and proportionality.
- Understanding HC/AC asymmetry in SGA fetuses is crucial for identifying those at higher risk.
Purpose of the Study:
- To determine the prevalence of HC/AC asymmetry in fetuses identified as small for gestational age (SGA).
- To compare the likelihood of adverse pregnancy and neonatal outcomes between asymmetric SGA, symmetric SGA, and appropriate for gestational age (AGA) infants.
Main Methods:
- Retrospective cohort study analyzing live-born singletons with antepartum sonography within 4 weeks of delivery.
- Derived a gestational age-specific HC/AC nomogram from a large database of nonanomalous singleton births.
- Defined asymmetric HC/AC as being at or above the 95th percentile for gestational age.
Main Results:
- Among 1364 SGA infants, 20% exhibited HC/AC asymmetry.
- Asymmetric SGA infants had a higher incidence of major anomalies, pregnancy-induced hypertension, and cesarean delivery for nonreassuring fetal heart rate compared to AGA infants.
- Neonatal complications (respiratory distress, intraventricular hemorrhage, sepsis, neonatal death) were more frequent in asymmetric SGA infants (14%) versus AGA infants (5%).
Conclusions:
- A minority of SGA fetuses with HC/AC asymmetry face increased risks for intrapartum and neonatal complications.
- Symmetric SGA infants did not demonstrate a significantly increased risk of morbidity compared to AGA infants.
- HC/AC asymmetry serves as a critical marker for identifying high-risk SGA fetuses requiring closer monitoring.
Objective:
To assess the prevalence of head circumference to abdomen circumference (HC/AC) asymmetry among small for gestational age (SGA) fetuses, and to determine the likelihood of adverse outcomes among asymmetric and symmetric SGA infants compared with their appropriate for gestational age (AGA) counterparts.
Methods:
In a retrospective cohort study, we analyzed consecutive live-born singletons of women who had antepartum sonography within 4 weeks of delivery and delivered between January 1, 1989 and September 30, 1996. A gestational age-specific HC/AC nomogram was derived from our sonographic database of 33,740 nonanomalous live-born singletons. Asymmetric HC/AC was defined as greater than or equal to the 95th percentile for gestational age.
Results:
Among 1364 SGA infants, 20% had asymmetric HC/AC and 80% were symmetric. Asymmetric SGA infants were more likely to have major anomalies than symmetric SGA infants or AGA infants (14% versus 4% versus 3%, respectively; P <.001). After exclusion of anomalous infants, pregnancy-induced hypertension at or before 32 weeks' gestation and cesarean delivery for nonreassuring fetal heart rate were more common in the asymmetric SGA than the AGA group (7% versus 1% and 15% versus 3%, respectively; both P <.001). A neonatal outcome composite, including one or more of respiratory distress, intraventricular hemorrhage, sepsis, or neonatal death, was more frequent among asymmetric SGA than AGA infants (14% versus 5%, P =.001). Symmetric SGA infants were not at increased risk of morbidity compared with AGA infants.
Conclusion:
The minority of SGA fetuses with HC/AC asymmetry are at increased risk for intrapartum and neonatal complications.