Increased risk of preeclampsia after use of paracetamol during pregnancy – causal or coincidence?

BACKGROUND: The maternal use of paracetamol during pregnancy has been associated with the development of preeclampsia. This study aims to clarify whether the connection is causal or whether it is due to reverse causation. METHODS: This study is a continuation of the retrospective case cohort study examining 2,508 pregnant women using a variety of drugs and the development of preeclampsia (1,252 women with preeclampsia and 1,256 controls). For the purposes of this study, more precise data was collected from several hospital databases of the women among this cohort who had reported taking paracetamol during pregnancy (indications, gestational period etc.); this was evaluated in association with the development of preeclampsia. RESULTS: 5.5% (100 cases and 37 controls) of all the study population (2,508) had clearly reported paracetamol use. Women with preeclampsia had used significantly more often paracetamol during pregnancy compared to controls (cases 8.0%, controls 2.9%, p < 0.001). The difference was most evident in the third trimester (after the 29th GW) and the use of paracetamol was associated with both mild and severe preeclampsia. Headache and “general pain” were the most common indications for medication among all paracetamol users. CONCLUSIONS: The use of paracetamol in the third trimester of pregnancy was associated with preeclampsia. This observation indicates that association between paracetamol use and preeclampsia is probably due to reverse causation, i.e. women with preeclampsia experience more headaches due to preeclampsia symptoms since this association was not detected with the use of paracetamol in earlier stages of pregnancy.