BackgroundIn Europe, 50%–60% of pregnant women uses paracetamol (Dafalgan). While its use in pregnan-cy was considered safe, recent studies show an associ-ation between prenatal exposure to paracetamol and increased incidences of autism, cryptorchidism, asthma and attention deficit hyperactivity disorder in a dose and duration dependent manner1-3. Data on transplacental transfer and metabolism of paracetamol are limited.MethodsIn an ex vivo placenta perfusion model (closed circuit) (n=38), maternal-to-fetal and fetal-to-maternal transplacental transfer of paracetamol (PCM) and its me-tabolites, paracetamol sulfate (PCM-S) and paracetamol glucuronide (PCM-G), was determined at a concentration corresponding to the maximum (PCM: 30 µg/ml; PCM-S: 10 µg/ml; PCM-G: 25 µg/ml) and steady state (PCM: 10 µg/ml; PCM-S: 5 µg/ml; PCM-G: 12.5 µg/ml) plasma con-centrations in normal clinical use. Antipyrine 100 µg/mL was added as internal control. PCM, PCM-S, PCM-G and antipyrine concentrations in perfusion medium and pla-cental tissue were determined using HPLC and LC-MS.Samples were taken at 0, 3, 6, 10, 15, 20, 30 min then ev-ery 15 min until 150 min followed by every 30 min until 210 (PCM) or 360 min (PCM-S and PCM-G). Fetal-to-ma-ternal and maternal-to-fetal ratios were normalised for antipyrine for each time point. Tissue accumulation and recovery of the compounds was calculated. Statistical dif-ferences were assessed using ANOVA.ResultsThe maternal-to-fetal as fetal-to-maternal trans-port of PCM was 44%–48%. For PCM-S, transplacental trans-fer was 38%–40% for maternal-to-fetal transfer and 28% for fetal-to-maternal transfer. PCM-G had a transfer of 31%–36% for maternal-to-fetal and 25% for fetal-to-maternal transfer. An equilibrium between the maternal and fetal concentrations was reached for PCM after 210 min for perfusion from maternal-to-fetal circulation. Fetal-to-ma-ternal transport of PCM-S and PCM-G was significantly slower then maternal-to-fetal transport. Extrapolation of maternal-to-fetal transport data till 360 min predict-ed equilibrium at 7.5 hour (PCM-S) and 9.5 hour (PCM-G). For fetal-to-maternal transport extrapolation of data till 210 min (PCM) and 360 min (PCM-S and PCM-G) predict-ed equilibrium for PCM after 270 min, PCM-S 36 hour and PCM-G 44 hour. PCM-S and PCM-G were converted to PCM by the placenta during the perfusions.ConclusionThis study shows that PCM rapidly crosses the placental barrier via passive diffusion for both mater-nal-to-fetal and fetal-to-maternal transplacental transfer. PCM-S and PCM-G, larger and more hydrophilic mole-cules, cross the placenta at a significantly lower rate. For PCM-S and PCM-G fetal-to-maternal transport is signifi-cantly slower than maternal-to-fetal transport.

BackgroundPregnant women and their fetuses are or-phan populations with respect to knowledge on safety and efficacy of drugs. It is estimated that over 90% of pregnant women uses over-the-counter or prescription medication.1 Albeit, data on transplacental transfer or fetal effects are still lacking for most of the medicines and food supplements. The ex vivo human placenta perfusion model is an effective and non-invasive method to study transplacental passage of drugs and environmental com-pounds in humans.2 It is the only method that retains the full structure of a full term human placenta, making it possible to study transplacental passage without harm-ing the foetus or the mother.3 Due to many challenges and its high complexity it remains difficult to incorporate it routinely into laboratories.MethodsA step-by-step protocol for the implementa-tion and validation of a closed-closed ex vivo perfusion model was developed. Different quality controls were implemented to ensure the integrity, viability and func-tionality of the method: (i). Antipyrine is a small drug molecule that does not bind to proteins and that passes the placental barrier by passive diffusion; It was used here to determine ‘overlap’ (solute exchange) between foetal and maternal circulation; (ii) the pressure and the flow rate in the foetal circulation as a marker for leakage; (iii) pH and glucose consumption were implemented as a marker for tissueviability.ResultsIn total 89 placentas were collected of which 34 placentas were successfully perfused with antipyrine and fulfilled all quality control measurements. A foe-tal/maternal antipyrine concentration ratio of 0.75 was reached within 89±21 min, while 210 min were required to achieve equilibrium. The foetal pressure remained un-der 70 mmHg during the entire experiment. The end foe-tal flow was 98% of the foetal starting flow. The average glucose consumption was 0.30±0.15 µmol/min/g. Every 30 min the maternal pH declined to 7.29±0.06 and was adjusted to 7.4. The foetal pH stayed stable at 7.30±0.05.ConclusionBased on the multiple quality control mea-surements, the described method of a closed human ex-vivo placenta perfusion model was validated. The success rate (38%) was more than twice the success rate reported in literature (15%).