Gestation Calculator

This calculator has been designed to give you an idea of the treatment options available to you*. If you decide to have an abortion with Marie Stopes UK, one of our nurses will give a more approximate gestation date during your appointment by way of a scan.
*Please note that this online calculator will only give you an estimated gestation based on the details you have provided.

Please select the first day of your last menstrual period.



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What are the failure rates and risks of an abortion?

No clinical procedure is risk or side-effect free. While there's a low risk of problems (complications) happening during an abortion, they're important for you to know about.

Generally, abortions done in the first 12 weeks (first trimester) of pregnancy have the lowest risk. Abortions done after 12 weeks have a higher risk of complications. If you have an abortion in a safe, clinical setting like a Marie Stopes centre you're at a low risk of complications. We strongly advise that you do not order tablets from the internet as this can pose a serious risk to your health.

Marie Stopes United Kingdom carries out two types of abortion: medical (the abortion pill) and surgical.

Risks and failure rates of medical abortion

Most women experience no complications when having a medical abortion. However, you will experience bleeding and strong cramps (like period pains) that can last for several weeks. While uncomfortable, this is completely normal and easily managed with painkillers and sanitary pads.

Side effects you might experience: diarrhea, nausea, vomiting, dizziness, warm flushes, chills, headaches and pains. Medical abortion can also worsen symptoms of migraines and asthma in some people.

There can be other complications  - but these are very rare. These are: 

  • Heavy bleeding/haemorrhage requiring a blood transfusion. This is a very rare complication but if you're experiencing heavy bleeding after a medical abortion you should attend an emergency department immediately.
  • ‘Incomplete abortion’, where some pregnancy tissue remains in the uterus. If you have an incomplete abortion we can arrange for a further dose of medication, a surgical evacuation, or to watch and wait - depending on your assessment by a trained nurse. This happens in 2-3% of medical abortions.
  • Infection-Endometritis (infection of the lining of the womb) is a rare complication of medical abortion, occurring in 0.1-0.9% cases only.
  • ‘Failed abortion’: where the abortion drugs fail to work and the pregnancy continues. This happens between 1 and 14 in 1000 cases after medical abortion.
  • Thrombosis (Clots in the legs or lungs): This is a risk of being pregnant and a risk of any surgery. The risk increases with a higher gestation. 
  • Death: This is extremely rare after medical abortion and occurs in less than 1 in 10,0000 abortions.  

At Marie Stopes, we'll always ask for a medical history when you're planning a medical abortion to ensure your safety. Some clients may be more suitable for a surgical abortion due to pre-existing medical conditions, and some clients will be referred to the NHS if we feel it's safer for them to have their termination in a hospital. 

Risks and failure rates of surgical abortion

Surgical abortion is a procedure that uses gentle suction to remove the pregnancy tissue from the womb. This procedure is safer when it's done before 12 weeks gestation, and is associated with more complications later on in a pregnancy. We can do terminations up to 24 weeks at Marie Stopes UK. Surgical abortion can be done under a local anaesthetic, or conscious sedation, and is done under a general anaesthetic at higher gestations.  

Most women experience no complications when having a surgical abortion. However, you might experience minor abdominal pain and some mild vaginal discharge or bleeding after the procedure. This generally settles after a few days. 

The rate of major complications from surgically abortion has declined dramatically and in 2014 is now about 1 in 1000 abortions. 

The following risks are linked with surgical abortion:

  • Complications relating to the anaesthetic: These are rare, and would be discussed with you by the anaesthetist on the day of your termination.
  • Injury inside the body: Damage to the uterus (0.86-1.4 in 1,000 cases); damage to the cervix (less than 1 in 100 cases).
  • Haemorrhage: Blood loss requiring transfusion happens in approximately 0.5-2 cases in 1,000. This risk of haemorrhage increases to 4 in 1000 after 20 weeks.
  • Infection: Following abortion, infection can happen in up to 10% of women but this is usually not serious. We reduce your risk of infection at Marie Stopes by giving you antibiotics at the time of your termination.
  • Retained pregnancy tissue: This happens in less than 1% of abortions and usually requires another procedure or some medication to help remove the retained pregnancy tissue.
  • Failure of abortion: All abortions carry a small risk of failure, which may require a further procedure. This risk is approximately 2.3 in 1000 for surgical abortion.
  • Rhesus isoimmunisation: Women with a certain blood group (rhesus negative) are at risk of isoimmunisation after induced abortion. At Marie Stopes, we administer Anti-D to all women who are rhesus negative whether they have a medical or surgical abortion. This helps prevent problems for future pregnancies.
  • Thrombosis (Clots in the legs or lungs): This is a risk of being pregnant and a risk of any surgery. The risk increases with a higher gestation. 
  • Death: There is a very low risk of death with a surgical abortion - 3 in 100,000 cases at 13-15 weeks, and 12 in 100,000 cases after 21 weeks.

While it's important to know about complications, they are rare. If at any time you're concerned about symptoms you're experiencing, please call our 24-hour telephone advice line on 0345 122 1441 for advice and follow-up appointments.

Long term complications

Effects on future reproduction

It's unlikely that having an abortion will have any affect on your fertility - most women go on to have a normal pregnancy. There's some evidence that repeated surgical abortions are linked with a slight increased risk of miscarriage, but there's no evidence this happens with medical abortions.

Breast cancer

There has been no proven link between having an abortion and breast cancer.

Psychological effects

Following an abortion, it's completely normal to experience a range of feelings such as relief, guilt, regret, anxiety and sadness. For most women, these feelings fade after a few weeks or months. Serious emotional problems after an abortion aren't common. For many women, abortion is a way of coping with a personal crisis situation. At Marie Stopes we offer confidential, impartial counselling to all women. Find out more about our counselling services