Aspirin in pregnancy
Authors:   , bij de Weg Jeske Milou 
Published: January 2025

In chapter 2, we investigated aspirin resistance during and after pregnancy over time in a longitudinal cohort study. Four complementary tests were used. A considerable part of the 23 pregnant participants showed aspirin resistance, despite the variation found between participants within participants over time and between the different devices. Aspirin resistance rates up to 30.4% were found. We revealed a possible pregnancy-induced effect since aspirin resistance rates were higher during pregnancy than postpartum. In chapter 3, we hypothesized that a Prothrombin G20210A (FII) or a Factor V Leiden (FVL) mutation might inhibit the effect of low-dose aspirin due to probable increased platelet activity by these mutations. Data of the FRUIT-RCT with women with FII- or FVL-mutation were compared to the data of the participants the study in chapter 2. Platelet function was tested by PFA-200, VerifyNow® and TxB2. The FII-mutation carriers demonstrated higher on-aspirin platelet activity on the PFA-200 and VerifyNow® compared to the controls. The FVL carriers demonstrated similar on-aspirin platelet activity compared to the controls. These data suggest a possible increased on-aspirin platelet activity in FII-mutation carriers, indicating a suboptimal response to aspirin. In chapter 4, the effect of aspirin 80mg on platelet function in pregnancy compared to placebo was evaluated. Platelet function was measured in the second and third trimester of pregnancy with three tests. The results showed that aspirin 80mg has a clear inhibitory effect on platelet function during pregnancy compared to placebo. The effect was similar in the second and third trimester. In our study, no evidence of laboratory aspirin resistance was found. In chapter 5, a review of the literature on aspirin adherence during pregnancy was given. In 24.2% of the RCTs on the use of aspirin in pregnancy adherence was tested. Various methods were used of which pill count was most frequently performed. Seven studies set a definition of good adherence. Five studies investigated the association between adherence and pregnancy outcomes of which two studies found a possible association between good adherence and lower incidence of preeclampsia. Chapter 6 presented a randomized controlled trial evaluating the beneficial effect a mobile educative application about aspirin during pregnancy to standard counselling alone by caregivers. Aspirin adherence was tested with two validated questionnaires and tablet intake >90%. Similar results were found in the app group and the standard counselling group for both validated questionnaires. Tablet intake >90% was similarly high in both groups. The null-finding was mainly caused by the high baseline tablet intake which makes it difficult to significantly raise this rate with an intervention. In chapter 7, the implementation of aspirin in pregnancy among Dutch gynaecologists was evaluated over a five year time period. For all indications mentioned in the national guideline there was an increase in prescribing aspirin in 2021 in comparison to 2016. The improved implementation can probably be explained by the introduction of the national guideline in 2018 and several published trials confirming the risk-reducing effect of aspirin. In chapter 8, the implementation of aspirin among Dutch independently community midwives was described. The implementation of aspirin in pregnancy among community-midwives seems to be good. Practical issues with prescribing aspirin are common, since community midwives do not have the authority to make a prescription. In chapter 9, we investigated patients’ perspective on aspirin during pregnancy with a survey. The results elucidated that half of the women with a history of hypertensive disorders of pregnancy were not aware of the risk-reducing effect of aspirin in a consecutive pregnancy. Women prefer to receive this information by a gynaecologists, at the postpartum check-up or in the beginning of the consecutive pregnancy, both orally and written.