Venous thromboembolism (VTE - blood clots that form in deep veins or in the lungs) has been identified as a leading cause of death in economically developed countries for pregnant and recently-pregnant women.

There is evidence that clotting parameters can take up to 6 weeks to return to normal for women who have had term deliveries, however there is an absence of information on time taken for clotting parameters to normalise following abortion.

As such, existing guidelines are based solely on expert opinion and recommend durations of VTE prevention from as short as 7 days, up to 6 weeks following abortion.

All women are assessed for risk of VTE, but data are needed to inform an evidence-based approach to prevention of VTE in these women.

The findings from this pilot study have the potential to inform clinical guidance and possibly a larger study subsequently.

Sample population: Women who attend the abortion service at the Chalmers Centre to receive abortion assessment and abortion care. There will be 3 groups recruited based upon gestational age of pregnancy - Group 1: Gestation less than 10 weeks (10 participants), Group 2: Gestation 10+0 -13+6 weeks (10 participants), Group 3: Gestation 14+0-20+0 weeks (10 participants).

Information Sheet: All new patients attending the clinic will be given a copy of the participant information sheet, so that they have time to read about the study. The Information sheet will also be available on the 'research' section of the clinic website - all women are routinely directed to this page before attending clinic.

Approach by research staff: Following registration, all patients are taken for an ultrasound scan by a clinical support worker to confirm gestation. Following this, patients move to a waiting area until they can be seen for their assessment. While they are waiting, the clinic coordinator will ask the patient if they are happy to be approached by the researcher to discuss the study further. If they are happy to discuss further, the researcher will then approach and discuss the study in a private room.

Consent: If patients are happy to participate in the study, the researcher will then obtain written informed consent prior to their bloods being taken by clinic staff if bloods required for routine care, if no routine bloods are required, the researcher will obtain the blood sample. Participants will be asked if they are planning to use a hormonal form of contraception following their abortion - if yes, they would be asked to wait until they have had their second blood sample taken to commence or not taken forward into the study.

First blood test: This will be obtained on the day of clinic attendance and ultrasound scan. Blood samples (less than 20 ml) will be obtained and taken to the NHS Lothian laboratory at the Royal Infirmary of Edinburgh and for ClotPro thromboelastography point of care testing.

Second blood test: An appointment will be made to see the patient in Chalmers Centre or at their home to obtain a further blood sample to compare to the initial test. This will take place 10-14 days following mifepristone administration. For the repeat sample we will conduct a COVID-19 risk assessment and only invite them for return visit/home visit if:

1. The participant has confirmed they and close contacts are well and without suspicion of COVID-19.
2. The participant agrees to a home visit.
3. The research staff undertaking the home visit should be well and have had no known contact with a COVID-19 positive individual for the past 14 days.

If they are having an intrauterine contraceptive, implant or injection, the second blood sample can be taken when they come into clinic for this, to minimise the number of visits.

Comparison group: A comparison group, Group 4 (10 participants), who are healthy volunteers, recruited from sexual and reproductive health clinics at Chalmers Centre, will be asked to provide a single blood test for ClotPro and lab tests, and urine pregnancy test hCG to act as a nonpregnant comparison. These participants must not be using hormonal contraception and must not be pregnant. This group will be approached by clinicians working in the SRH clinics and the researcher will be on hand to obtain consent and then draw blood.

Inclusion Criteria:

Group 1:

• Pregnant and seeking abortion
• Gestation of pregnancy less than 10 weeks
• Healthy, no medical conditions

Group 2:

• Pregnant and seeking abortion
• Gestation of pregnancy between 10 and 14 weeks
• Healthy, no medical conditions

Group 3:

• Pregnant and seeking abortion
• Gestation of pregnancy between 14 to 20 weeks
• Healthy, no medical conditions

Group 4:

• Non pregnant
• Healthy, no medical conditions
• Able to speak English independently

Exclusion Criteria:

All groups:

• Unable to give informed consent
• Previous or current venous thromboembolism
• Current smoker
• Personal or family history of thrombophilia or haemophilia
• Taking medicines known to affect clotting parameters (e.g. Aspirin)

Groups 1-3:

- Planning to commence hormonal contraception prior to second blood test.

Group 4:

- Using hormonal contraception at baseline visit

Cisgendered women. Non-binary assigned female at birth and transgendered men would be considered as long as they are not using any hormonal therapy (cross-sex, blockers or otherwise)

Women seeking medical abortion at various gestations and non-pregnant comparator group.

As this is abortion-care research with small numbers of participants, we will not make individual level participant data available publicly. Should researchers required this data for meta-analysis (for example) they can contact the principle investigator and request will be considered on a case-by-case basis.