Clinical protocol
A maternal blood sample (5 mL) was obtained from each patient before
administering the first dose of BET esters to assess biochemical, renal,
hepatic, metabolic and haematological parameters. Laboratory tests were
carried out to assess the functional normality of the organ systems. All
pregnant women received a standard regimen of BET esters intramuscularly
(Celestone Soluspan®, Mantecorp, Anápolis, GO, Brazil – equal amounts
of BET sodium phosphate and BET acetate at a dose of 12 mg every, two
times 24h apart). Serial blood samples (5 mL) were collected immediately
before and 5, 10, 15, 35 minutes and 1, 3, 6, 8, 10, 16 and 24 hours
after the first intramuscular BET esters dose to determine BET plasma
concentrations. In some cases, there was a failure to stop labour and
delivery occurred (n=5). Simultaneous samplings of maternal blood,
umbilical cord (for each fetus if twin pregnancy), and intervillous
space (the space near the umbilical cord insertion if twin pregnancy)
were performed to assess the placental transfer and distribution of BET
in these compartments. Blood was collected from the umbilical cord after
the cord was clamped and sectioned and the placenta expelled through the
birth canal, with no risk for the mother or neonate. The technique
described by Camelo Júnior et al. was adopted to collect blood samples
from the umbilical vein and the intervillous space.24
All blood samples for BET pharmacokinetics and transplacental transfer
studies were transferred to heparinized tubes protected from light and
containing 10 µL of stabilizing solution of 2 M of sodium arsenate
dibasic heptahydrate. The blood samples were then centrifuged within a
maximum period of 15 minutes at 21.500 ₓ g for 5 minutes at 4°C. The
plasma was separated and transferred to cryogenic tubes containing 10 µL
of a stabilizing solution of potassium fluoride 50% and were stored at
-70°C until analysis.25,16