Small fetal size before 20 weeks' gestation: associations with maternal tobacco use, early preterm birth, and low birthweight.
OBJECTIVE
The objective of the study was to determine whether small fetal size before 20 weeks' gestation is associated with preterm birth (PTB), low birthweight (LBW), and poor fetal growth.


METHODS
A total of 4405 singleton pregnancies at 10-19 weeks' gestation (GA) based on a known last menstrual period (LMP) were evaluated. Ultrasound-estimated GA (US-GA) was calculated based on crown-rump length at 10-13 weeks and by femur, head, and abdominal measurements from 14 to 19 weeks. The outcomes were compared between small (1-10 days smaller than LMP-GA) and large (0-10 days larger than LMP-GA) fetuses.


RESULTS
At 10-19 weeks, small fetuses measured 2.7 days younger and were more likely to have mothers who smoked (P = .004). Small fetuses had no more PTB (11.4 vs 12.1%, P = .47) but did have more early PTB before 34 (5.4 vs 4.3%, P = .07) and before 32 weeks (4.1 vs 2.7%, P = .009). Small fetuses had lower birthweights (BWT), more frequent BWT below 2500 g (13.0 vs 8.6%), below 1500 g (4.0 vs 2.4%), and below 1000 g (2.9 vs 1.4%) as well as BWT below 2500 g at term (4.9 vs 2.3%) and BWT less than the 10th percentile (8.8 vs 3.7%), P < or = .003 for each. Small fetuses at 10-19 weeks also had less frequent macrosomia and were less frequently large for gestational age at birth (P < .0001 for each). These findings largely persisted in multivariable analyses.


CONCLUSIONS
Small fetal size at 10-19 weeks is associated with tobacco use in pregnancy, early PTB, LBW, and poor fetal growth.
Mercer
Brian M
BM
Department of Obstetrics and Gynecology, Case Western Reserve University School of Medicine, MetroHealth Medical Center, Cleveland, OH, USA.
Merlino
Amy A
AA
Milluzzi
Cynthia J
CJ
Moore
John J
JJ
D000328:Adult; D049628:Body Size; D018568:Crown-Rump Length; D005260:Female; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging*; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008425:Maternal Behavior; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D047928:Premature Birth / Q000209:etiology*; D012189:Retrospective Studies; D012907:Smoking / Q000009:adverse effects*; D016216:Ultrasonography, Prenatal