Physical consequences of abortion

Immediate complications of abortion

Does abortion cause breast cancer?

Does abortion cause preterm birth?

Does abortion cause infertility?

Does abortion cause sexually transmitted disease?

Immediate complications of abortion

Immediate complications of abortion happen are very common. Almost all complications are much more common at later gestations. Some are much more common in medical abortion (e.g. haemorrhage), while others are much more common in surgical abortion (e.g. uterine perforation).

More rarely, abortion can cause uterine rupture. This is more common with a history of caesarean section, after which the risk can be up to 0.4%. Uncommon, though not rare, in the case of surgical abortion are uterine perforation (generally around 0.1% in first trimester and much higher later) and cervical trauma (generally 0.05-0.1% in first trimester, just over 1% in second trimester): “Women must be informed that, should one of these complications occur, further treatment in the form of blood transfusion, laparoscopy or laparotomy may be required.”


Haemorrhage after abortion, especially medical abortion, is common or very common. Studies on haemorrhage vary widely, partly because of poor reporting and different definitions of haemorrhage. The RCOG claim that national data show <0.2% of abortions involve haemorrhage, but Department of Health data are known to massively underreport abortion complications, so these data are not only useless; they barely constitute data at all. Freedom of Information data from individual hospitals has shown a 2.3% rate for haemorrhage treated in hospital. Data from Finland, which has some of the most complete reporting and record-linkage systems in the world, found 2.1% haemorrhage rate for early surgical abortion and 15.6% for early medical abortion. 2%, for comparison, would mean around 4,000 women a year in the UK alone. A total complication rate was found of 5.6% for early surgical abortions, and 20% for early medical abortions, with 4% having multiple adverse events. There were 4 deaths in 20,000 surgical abortions and 2 deaths in 22,000 medical abortions. Bear in mind everything said in the question on mortality rates, and the fact that these abortions were all under 9 weeks – abortions beyond this point are significantly riskier.

It is clearly true that haemorrhage rates differ massively in the literature depending on gestation, reporting ability, and definition of haemorrhage. But the rates are still substantive in the first trimester and only get worse later, and underreporting will always mean that the true rates are higher than reported. High haemorrhage rates are often downplayed by selecting very stringent criteria (e.g. requiring transfusion). This appears to be selective, given that no such stringent criteria were used to cancel a study on abortion pill reversal and disparage abortion pill reversal as dangerous because of the ‘haemorrhage’ risk. This is despite the fact that only one patient needed a transfusion (as occasionally happens in abortion generally), and this was a patient in the control group – no one who had progesterone to attempt to reverse the abortion needed a transfusion. Still, it was said that there were too many haemorrhages and the issue could not be explored further – with abortion pill reversal subsequently being smeared as dangerous in the media (my view on abortion pill is cautiously positive: I think better data are needed, but there is certainly provisional evidence for it, and no convincing evidence against its safety – see ‘Does abortion pill reversal work?’).

The reality is that whether or not a haemorrhage exceeds 500ml or requires transfusion, it is an adverse event which can be distressing to women, require emergency transport and observation/treatment in hospital, and which can be dangerous with baseline anaemia. It cannot be dismissed – and it is common or very common. Severe haemorrhage requiring transfusion is less common, but we have minimal reliable data on this question, since complications are often underreported and haemorrhage is often not specified in detail. Still, it certainly happens with relative frequency. For example, RCOG cite a study showing that 0.7% of medical abortions from 13-21 weeks required transfusion.


As with haemorrhage, infection is often underreported and studies vary significantly in estimates. However, even the RCOG concedes rates may be as high as 10%, making infection a common complication of abortion. The comprehensive Finnish data suggest this is the same between medical and surgical abortion – 1.7% infection rates were found in that study. This would work out to around 4,000 women each year in the UK, or potentially higher if underreported and if the estimates closer to 10% are accurate.

Authorities like the RCOG typically claim that infertility is not a consequence of uncomplicated induced abortion. But that is of no use to the woman who have an abortion complicated by infection, for whom there is no dispute that they are at risk of pelvic inflammatory disease, infertility and ectopic pregnancy. Given that infection after abortion is common, this is a serious consideration.

Incomplete abortion and continuing pregnancy

Incomplete abortion is, perhaps apart from haemorrhage, the most common complication of abortion, to which continuing pregnancy (i.e., the baby is still alive) is obviously related. Incomplete abortion – where the baby dies but is not fully expelled – poses a risk of infection and bleeding and hence needs to be treated, usually by surgical evacuation.

The RCOG report continuing pregnancy rates of 0.9% for medical abortion and 0.5% for vacuum aspiration. Again, this dramatically increases as gestation increases. The RCOG refers to a variety of studies suggesting around 5-6% surgical intervention rate after medical abortion, which fits with the Finnish data, Marie Stopes Australia data and UK Freedom of Information data. This would work out to about 12,000 women needing surgical evacuation each year in the UK. The rates for surgical evacuation after surgical abortion are significantly low, but it is still common.

The main systematic review examining the safety of telemedicine abortion reports a wide range of estimates for incomplete abortion or continuing pregnancy, again likely due to underreporting. Several studies show surgical evacuation rates of 10-20% even at early gestations, making this very common.

Hence, immediate complications after abortion are common to very common.

Does abortion cause breast cancer?

I am not in a position to say. Before making claims of this significance, it is important to be very familiar with the data and confident that you can draw conclusions from it. Since I have not yet looked at this literature in great detail, I will make no claim about whether abortion causes breast cancer; I think this is the intellectually honest approach to take. Hence I will say very little on this question and include it only for completeness.

What does seem relatively uncontroversial is that earlier age at first full-term pregnancy is associated with a reduced risk of breast cancer, as does a higher number of births. The standard view seems to be that this is a causal link, not an artefact of some confounding factor. Hence, insofar as abortion prevents a birth, it would seem to increase one’s risk of breast cancer relative to giving birth, even if not relative to someone who has not become pregnant. So far, I have not come across anyone disputing this specific claim – but I would be grateful if someone could show me otherwise. When authorities claim that abortion does not cause breast cancer, they seem (in every case I have found, but again I am open to correction) to be saying that it does not cause breast cancer relative to non-pregnant women. That says nothing about whether it removes the protective effect of giving birth, which appears to be relatively uncontroversial. So specification of the comparison class seems crucially important on this question.

Does abortion cause preterm birth?

Abortion is uncontroversially associated with preterm birth and low birth weight in future pregnancies. The main systematic review on the topic found an association with a dose-dependent effect – the more abortions, the higher the increased risk, from 36% from one abortion, to 93% for more than one abortion. Although the RCOG claim that there is insufficient evidence implying causality, the leading theories (e.g., instrumentation of the cervix and uterus, as suggested by RCOG) involve a causal relationship. Of course, this should be researched further.

The increased risk of very early preterm births is even higher. It has been estimated that abortion is responsible for around 23,000 very early preterm births each year in the US, around 1,000 extra cases of cerebral palsy each year as a result, and costs of $1.2 billion in neonatal costs alone (not including later costs of long-term disability). For context, preterm birth is the leading cause of death for children under 5 globally.

Does abortion cause infertility?

There is no dispute that abortion can cause infertility, despite some sources denying this. Abortion can cause pelvic inflammatory disease if complicated by an infection, and PID in turn can cause infertility. Whether abortion causes infertility at a higher rate than pregnancy does is more controversial.

Does abortion cause sexually transmitted diseases?

Not directly, as far as anyone knows. But the legalisation of abortion certainly increases their overall transmission. The reason is that abortion acts as insurance option against pregnancy, meaning that the overall expected cost of having sex is significantly reduced – abortion is always there if contraception fails, so people are more willing to have sex with people, and more willing to have multiple sexual partners. They are also less likely to use barrier contraception. As a result, the legalisation of abortion in a wide variety of countries has been shown in multiple studies to lead to a significant increase in sexually transmitted diseases – Klick and Stratmann estimate a 60% increase in gonorrhoea transmission as a result, for example, complications of which include pelvic inflammatory disease, infertility, miscarriage, and premature labour. They estimated that the additional costs of treating STDs from abortion’s legalisation could cost around £4 billion each year in the US alone. These costs are presumably significantly higher in areas with higher HIV prevalence, including, of course, the costs of death from AIDS. This is part of the explanation for South Africa’s massive increase in maternal deaths from HIV/AIDS following the legalisation of abortion in the mid-1990s.

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