Amniotic fluid insulin at 14-20 weeks' gestation: association with later maternal glucose intolerance and birth macrosomia.
OBJECTIVE
To examine the hypothesis that early second trimester amniotic fluid (AF) insulin concentration is elevated and later fetal growth is augmented in gravidas demonstrating later oral glucose intolerance.


METHODS
In this prospective observational cohort study, AF was sampled at 14-20 weeks' gestation in 247 subjects, and 1-h 50-g oral glucose challenge tests (GCTs) were performed at > or = 24 weeks. AF insulin was assayed by an automated immuno-chemiluminometric assay (8). Macrosomia was defined as birth weight above the 90th centile.


RESULTS
AF insulin concentration (range 1.4-44.5 pmol/l) correlated positively with gestational age and maternal weight. A logistic regression analysis, adjusted for maternal age and midpregnancy weight, showed increased AF insulin multiples of gestational age-specific medians to be associated with subsequently diagnosed gestational diabetes mellitus (GDM) (OR 1.9, CI 1.3-2.4, P = 0.029). Among 60 subjects with GCT values > 7.2 mmol/l, each unit increase in AF insulin multiple of median (MOM) was associated with a threefold increase in fetal macrosomia incidence (3.1, 1.3-4.9, P = 0.048).


CONCLUSIONS
An elevated AF insulin concentration at 14-20 weeks' gestation is associated with subsequently documented maternal glucose intolerance. Among gravidas with GCT values > 7.2 mmol/l, elevated early AF insulin concentration is associated with fetal macrosomia. Maternal glucose intolerance may affect fetal insulin production before 20 weeks' gestation.
Carpenter
M W
MW
Department of Obstetrics and Gynecology, Brown University School of Medicine, Providence, Rhode Island, USA. mcarpent@wihri.org
Canick
J A
JA
Hogan
J W
JW
Shellum
C
C
Somers
M
M
Star
J A
JA
D000649:Amniocentesis; D000653:Amniotic Fluid / Q000737:chemistry*; D001331:Automation; D001724:Birth Weight; D015331:Cohort Studies; D016640:Diabetes, Gestational; D005260:Female; D005320:Fetal Macrosomia / Q000175:diagnosis*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007328:Insulin / Q000032:analysis*; D007621:Karyotyping; D008163:Luminescent Measurements; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011446:Prospective Studies; D012016:Reference Values; D012044:Regression Analysis; D015203:Reproducibility of Results
D007328:Insulin