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