Introduction
During the past decade, the rate of twin pregnancies has remarkably
increased, and this is mainly ascribed to the rise in maternal age and
the improvements in fertility enhancing treatments.1-3A common adverse outcome for twin pregnancies is intertwin birthweight
discordance, defined as the
birthweight discrepancy divided by the birthweight of larger twin and
multiplied by 100.4 Birthweight discordance has been
reported to be related to an increased incidence of fetal intrauterine
death, neonatal neurological morbidities, respiratory distress,
infection, abnormal acid-base status, or necrotizing
enterocolitis.4,5
Though the cause and pathophysiology of rising birthweight discordance
in twin pregnancies are not completely understood and mastered,
recent studies ascribed it to
chorionicity,6 parental race,7maternal vitamin D levels,8 total birthweight,
maternal age, education, fetal sex,9 weight gain
during pregnancy10 and GHD.
Gestational hypertensive disease
(GHD), classified into gestational hypertension (GH), preeclampsia (PE),
eclampsia and chronic hypertension (CH),11,12 is one
of the most common disorders in pregnancy and
its incidence in twin pregnancies is
at least double greater than in singletons.13,14 The
risk of PE was 2.3% in singletons, 8.1% in dichorionic (DC) twin
pregnancies and 6.0% in
monochorionic (MC) twin
pregnancies. GHD is well recognized as a major
risk factor for maternal morbidity,
perinatal mortality and preterm delivery.14,15For singletons, the relationship
between GHD and fetal growth
anomalies has been well established.16 However,
studies investigating the association between GHD and birthweight
discordance in twin pregnancies have reported differing results. In
spite of the previous negative findings that the risk of intertwin
birthweight discordance was similar between pregnancies with GHD and
normotensive ones,17-19 some other reports have shown
that the degree of intertwin birthweight discordance in twin pregnancies
is directly correlated with the risk of GHD.20-26
It is crucial to clarify the impact
of GHD on intertwin birthweight discordance, as increased risks of
perinatal outcomes are associated not only with GHD itself, but also
with intertwin birthweight discordance.4,27-29Therefore, the aim of this systematic review was to explore the
association between GHD and birthweight discordance in twin pregnancies.