What is a Saline or Instillation Abortion?
An instillation abortion refers to any abortion where medication is injected or “instilled” into the uterus (womb), either inside or outside the amniotic sac that holds the fetus. Saline abortion is a specific type of instillation abortion, and the technical name is hypertonic saline abortion. Hypertonic saline is a highly concentrated salt solution. Other types of medications that can be instilled are urea, prostaglandins, and prostaglandin analogues. 
History of Instillation Abortion
Hypertonic saline was the first type of instillation abortion. Starting in the 1960s, saline abortions were typically done during the 2nd trimester because the uterus was easier to puncture at that gestational age.  Hyperosmolar urea, a highly concentrated kidney waste product, was also used for instillation abortions around the same time. 
Both these types of instillation abortion fell out of favor in the 1970s and 80s because of serious complications. Several otherwise healthy women died after having them, and many abortions failed and ended up as live births. One study found that saline abortions were effective only 74% of the time. In other words, there were 26 failed abortions in every 100 women. 
As hypertonic saline and urea phased out, abortion doctors switched to instillation of prostaglandins. Prostaglandins are chemical messengers produced naturally by the body for different purposes. These purposes include: muscle contraction, blood clotting, inflammation, pain perception, the gastrointestinal or GI system, and other things. Prostaglandins also had many side effects, including strong GI symptoms like nausea, vomiting, and diarrhea. The latest version of instillation abortion, starting around the 1990s, is prostaglandin analogues. Prostaglandin analogues are slightly chemically modified versions of prostaglandins with fewer side effects.
Overall, prostaglandin analogues are routinely used nowadays, but they are not usually given by instillation. They are more likely to be given as pills, such as Misoprostol (see Medication Abortion article) because they have fewer side effects that way.
What Percentage of Abortions are Instillation Abortions?
Most Recent Data
A CDC report from 2007 reported that 0.5% of abortions that year were instillation abortions, which includes instillation of different substances: hypertonic saline, urea, prostaglandins, and prostaglandin analogues. The CDC website also reported that their abortion estimates were off by 35% from the Guttmacher Institute numbers. Guttmacher Institute numbers are considered the most accurate source for abortions statistics in the United States. Theoretically, then, the actual number of abortions for the year would have been around 1.2 million, and about 12,000 of those would have been instillation abortions.
The most recent abortion numbers available are from 2014, but CDC numbers for that year do not break down types of abortion the way that the 2007 report did. They report 652,639 abortions total, and almost 47,000 abortions in the second trimester. If roughly 1% of those were instillation abortions, that would be around 6,000.  If the numbers are adjusted for Guttmacher estimates, there were just under 1 million abortions and around 10,000 of those were instillation abortions.
Instillation Abortions mostly done in the Second Trimester
The National Abortion Federation textbook, published in 2009, reports that in 1974 57% of abortions done after 13 weeks gestation were instillation abortions. By 2005, they estimated that number to be 0.4%. 
What happens during an Instillation Abortion?
Instillation as part of Induction Abortion
Instillation of medications is often done as part of an induction abortion. Usually, being “induced” means that a woman is given medications to make her go into labor and deliver the fetus at a specific time, often before the due date. This is done for a variety of reasons, such as if the mother’s blood pressure is getting too high, or the fetus is not growing properly in the womb anymore.
In an induction abortion, the plan is to go into labor but to deliver a dead baby. Instillation of medications causes fetal death and speeds up the labor process by softening the cervix and causing contractions. Instillation-before-induction abortions are done in hospitals.
Before the Abortion
Before the abortion, the woman has bloodwork and sexually transmitted infection screenings done. Vital signs like blood pressure and heart rate and temperature are recorded. An ultrasound will be done to confirm how far along she is. She may be given an antibiotic pill to prevent infection of the cervix, vagina, and uterus.
Often, her cervix will be dilated using laminaria, sticks of sterilized seaweed. This may be done up to 24 hours before the instillation.
An injection is given into her abdomen (stomach area) to numb the skin around the needle. Next, the abortion doctor uses ultrasound to guide a long needle through the abdomen and into the uterus. Approximately one cup of amniotic fluid is removed to be sure that the needle is in the right place, and it is replaced with hypertonic saline or another medication. Inside the uterus, the medication is either injected into the amniotic sac that contains the fetus or into the space outside of the sac.  Afterwards, labor inducing medications may be given through an IV. Typically, the woman will go into labor and deliver the dead fetus within about 24 hours.
At what point does the fetus die during the Abortion?
Instilled medications work in different ways. All ways are meant to kill the fetus before it is delivered. Hypertonic saline and urea cause severe dehydration, burning of the fetal skin and internal organs, and then death. The prostaglandins and prostaglandin analogues similarly break down the fetal tissue. This causes death, softens the cervix, and stimulates uterine contractions.
What are the Side Effects of an Instillation Abortion?
Hypertonic saline and urea instillation abortions can cause side effects:
- Babies born alive, sometimes with deformities or other health problems
- A life-threatening blood clotting disorder called disseminated intravascular coagulopathy (DIC)
- Life-threatening hemorrhage (bleeding) 
For example, 3 otherwise healthy women died in 1966 due to seizures after saline abortions. Hypertonic saline is a highly concentrated sodium (salt) solution. If it leaks out of the uterus and into the bloodstream, it causes major problems for the woman. Besides leaking out through a hole (or perforation) punctured in the uterus, the medication can also be accidentally instilled into the bloodstream instead of the uterus. In the bloodstream, the salt solution travels throughout the body. Too much sodium in the brain causes severe swelling and bleeding. Severe swelling and bleeding can cause seizures and ultimately death.  Hypertonic saline accidentally given into the bloodstream can also cause a life-threatening blood clotting disorder called disseminated intravascular coagulopathy (DIC).
Prostaglandins and prostaglandin analogues can cause:
- Severe abdominal pain
- Shivering 
- Vaginal bleeding, sometimes requiring blood transfusion 
- Cervical fistulae (abnormal opening between the cervix and the vagina or bladder causing leakage of urine) 
- Uterine rupture (can be life-threatening), typically in women who had previously had a Cesarean section (C-section) 
Induction abortions are specifically associated with retained placenta, which puts the woman at risk for life-threatening infection.
How often do Complications occur?
Life threatening blood clotting and bleeding after prostaglandin analogue abortion occurs in approximately 1 in every 100 women.  Research has shown that induction abortions can be complicated by retained placenta up to 30% of the time. 
While only about 10–15% of all abortions are done in the second trimester, they are responsible for roughly two-thirds or 66% of all major complications.  Risk of death from second trimester abortion is over 20 times higher than from first trimester abortion.  Risk of death from abortion increases by 38% each week starting in the second trimester. 
 Many research studies and resources cited in this document are from the 1970s and 1980s because more recent research on instillation abortions has not been done.
 While most sources are from the 1970s and 1980s, one case report from the United Kingdom of a urea instillation abortion was published in 2009.
 Cassing Hammond MD, and Stephen Chasen MD, “Dilation and Evacuation,” Management of Unintended and Abnormal Pregnancy. Ed. Paul, Lichtenberg, Borgatta, Grimes, Stubblefield and Creinin. (Wiley-Blackwell, 2009), 158.
 Berger, G., Bygdeman, M., and Keith, L.G. Prostaglandins and their Inhibitors in Clinical Obstetrics and Gynaecology. (Springer Netherlands, 1986), 297.
 Autry AM, Hayes EC, Jacobson GF, Kirby RS. A comparison of medical induction and dilation and evacuation for second-trimester abortion. Am J Obstet Gynecol 2002; 187: 393– 397.
 Cassing Hammond MD, and Stephen Chasen MD, “Dilation and Evacuation,” Management of Unintended and Abnormal Pregnancy. Ed. Paul, Lichtenberg, Borgatta, Grimes, Stubblefield and Creinin. (Wiley-Blackwell, 2009), 179.