26 Yukari Asamiya, Ken Tsuchiya and Kosaku Nitta
cohort was 36.2 ± 3 weeks and the mean birth weight was 2417.5 ± 657g.
Hladunewich et al. reported, in a Canadian and American cohort in 2014, that
there was a significant dose-response relationship between the HD intensity
and live birth rate, which improved from 48% in women receiving <20 hours
HD, to 75% in women receiving between 21 and 36 hours, and to 85% in
women receiving ≥37 hours of HD each week [13].
Recently, in 2015, an Italian group described that women on dialysis
should be advised that there is at least a 75% chance of success by intensive
dialysis treatment and that they should be kept under a strict clinical course;
the authors strongly recommended that a dialysis schedule of 6-7 days (with an
ideal target of at least 36 hours) per week should be offered during pregnancy
to, at least, patients without residual renal clearance [14, 15]. The dialysis
schedule should be adjusted according to the renal function and uremic waste
product levels in the blood. However, intensive dialysis still faces some issues.
First, a nocturnal dialysis program (at home or in a center) cannot be offered
everywhere due to the required facilities and staff not being readily available,
and intensive dialysis is not always covered by health insurance. Second,
overworking the mother may result in reduced motivation during the
progression of the pregnancy.
UREA TOXINS AND PREGNANCY
The blood in patients with end-stage renal disease (ESRD) contains many
accumulating uremic waste products. Among the different dialysis modalities,
hemodiafiltration is superior to HD for the removal of middle-molecule
substances. Adequate verification of the status of all of uremic waste products
in terms of transplacental transfer and potential harmful effects on the fetus
has not been performed, and future studies are thus required. Accordingly,
there are currently limited available data regarding the most appropriate
dialysis modality, HD or hemodiafiltration, during pregnancy. However, at the
present time, HD is the standard extracorporeal treatment in pregnancy,
suggesting at least equal benefits of the two modalities [14]. Our group has
previously shown that the maternal urea nitrogen (UN) levels were
significantly and negatively associated with gestational age and birth weight
[16] and, in line with these data, another study revealed that a high level of
maternal serum UN was associated with poor fetal outcomes [17]. Therefore,
among the various uremic toxins, the maternal serum UN level is currently
used as an important marker associated with gestational age, birth weight and