1.INTRODUCTION
FGR accounts for approximately 5%–10% of singleton pregnancies1. This growth disorder is associated with an
increased risk of APO and long-term impacts2
3. At present, prenatal recognition of
small size by ultrasound, which minimizes rates of APO to some extent,
is the most commonly method for identifying intrauterine growth
disorders. However, it still fails to detect more than 25% of
late-onset FGR 4-6. One possible reason for failure to
identify late-onset FGR is that the ultrasound examination was done in
the early third-trimester pregnancy6
7.
The feto-placental circulation is crucial for fetal development and
growth. At present, the umbilical artery (UA) Doppler studies, including
the umbilical pulsatility index (UA-PI) and the ratio of the systolic
peak value and the end-diastolic velocity of the umbilical artery
(UA-S/D), is the primary method for evaluating feto-placental
circulation. However, as reported by some published studies, placental
insufficiency in late-onset FGR often goes undetected by UA Doppler scan8
9, which brings a problem in assessing
APO of those SGA infants. It is now widely acknowledged that large
numbers of near-term SGA infants with normal UA Doppler studies are
identified as late-onset FGR, which are at risk of APO10-12.
It is widely known that the placental volume blood flow is reduced in
FGR. The decrease of placental volume blood flow might even occur before
the increase of UA-PI in the fetuses with growth restriction13. One longitudinal study reported that the UA
velocities can reflect placental blood flow and thus the feto-placental
circulation 14. However, to the best of our knowledge,
whether the UA velocities are decreased in FGR has not been determined.
Therefore, the main purpose of this study was to investigate the
discordances of UA velocities in the FGR, SGA and AGA with normal UA
Doppler at 37 weeks’ gestation, and to investigate the value of UA
velocities for predicting FGR. We hypothesized that the UA absolute
velocities might be decreased with the severity of growth restriction,
even in those with normal UA Doppler, which can contribute to an early
prediction of FGR with normal UA Doppler.