Prior Cesarean and Ectopic Pregnancy

Ectopic pregnancy, image from Wikimedia Commons.
Blue arrows point to the uterus, while the red arrows
point to a tubal ectopic pregnancy with bleeding

Each year, as part of Cesarean Awareness Month, I highlight how a high cesarean rate often has unforseen implications on public health. Today let's talk about ectopic pregnancy.

Ectopic pregnancy is a pregnancy where the fertilized egg implants outside of the inner uterine lining. Although most are caught early and resolved safely today, it is a potentially life-threatening complication and needs to be taken seriously.

Brand-new research suggests that multiple prior cesarean sections are yet another risk factor for ectopic pregnancy.

Ectopic Pregnancy Primer

Ectopic pregnancies are usually "tubal pregnancies" where the fertilized egg implants in the Fallopian tubes on the way from the ovary to the uterus. However, ectopic pregnancies aren't always tubal. They can also implant in the ovary, cervix, or abdominal cavity.

Because these locations cannot usually accommodate a growing pregnancy for long, the big risk from ectopic pregnancy is rupture and bleeding. If this occurs, it is a true, life-threatening emergency. The American Academy of Family Physicians (AAFP) states that ruptured ectopic pregnancies still accounts for 10-15% of all maternal deaths in pregnancy.

In the developed world, most ectopic pregnancies are caught and treated early, resulting in improved outcomes. However, in the developing world, diagnosis of ruptured ectopic pregnancies is often delayed, and as a result, mortality is much higher. Wikipedia notes that in Africa, "ectopic pregnancies are a major cause of death among childbearing women."

About 1 in 50 pregnancies are ectopic. One source notes:

The major health risk of ectopic pregnancy is rupture leading to internal bleeding. Before the 19th century, the mortality rate (death rate) from ectopic pregnancies exceeded 50%. By the end of the 19th century, the mortality rate dropped to five percent because of surgical intervention. Statistics suggest with current advances in early detection, the mortality rate has improved to less than five in 10,000. The survival rate from ectopic pregnancies is improving even though the incidence of ectopic pregnancies is also increasing. The major reason for a poor outcome is failure to seek early medical attention. Ectopic pregnancy remains the leading cause of pregnancy-related death in the first trimester of pregnancy.

Risk factors for ectopic pregnancy may include:

• Previous ectopic pregnancy
• Pelvic Inflammatory Disease (often caused by Sexually Transmitted Diseases such as chlamydia or gonorrhea)
• Infertility and/or Fertility treatments such as IVF
• Previous tubal or pelvic surgeries
• Abnormal Fallopian Tubes (due to congenital abnormalities or exposure to DES)
• Cigarette smoking
• Possibly endometriosis

A prior ectopic pregnancy is the greatest risk factor for a current one. However, anything that creates an infection or scarring can interfere with the usual action of the "cilia" (the little hair-like projections along the Fallopian tubes that help push along a fertilized egg to the uterus), causing the fertilized egg to implant too early.

Now it looks like cesareans are also a modest risk factor for ectopic pregnancies. It is unknown why there may be a connection, but the most likely scenario is probably infection.

Another possibility is the development of adhesions (scar tissue), sometimes known as Asherman's Syndrome, which might also predispose the fertilized egg to implant in the Fallopian tubes or cervix. Since Asherman's Syndrome can occur after a D&C, damage to the uterine lining from manual removal of the placenta during a cesarean is also plausible.

It's also important to note that there is another sub-type of ectopic pregnancy where the fertilized egg implants in the cesarean scar itself, called a "cesarean scar pregnancy," which we have written about before. In this situation, if the fertilized egg implants near damage to the uterine lining from the cesarean scar, the placenta may implant too deeply into the uterine wall or the fetus may even extrude into the abdominal cavity. The rate of cesarean scar pregnancy has risen significantly in recent years in conjunction with the rising cesarean rate.

One in a great while, there is also a "heterotopic pregnancy," where one fertilized egg implants normally inside the uterus, while another implants outside of the uterus or in a cesarean scar, threatening the intrauterine pregnancy. Fertility treatments are a significant risk factor.

Cesareans and Ectopic Pregnancy

Now, recent research shows that more than one prior cesarean substantially increases the risk for ectopic pregnancy.

The strength of this study was that its data was drawn from multiple hospitals over several years, so the large data group is more likely to show a real risk relationship. Population-wide studies are needed to confirm this relationship, however.

Some previous studies have shown a modest correlation between prior cesarean and ectopic pregnancy. Other studies have found no correlation. However, these studies were small or of variable quality, and may not have differentiated by number of prior cesareans. This study found a significant risk only after 2 or more prior cesareans.

As always, it's important to keep the numerical risks in perspective. The actual risk isn't huge. Even with multiple prior cesareans, most women will not experience an ectopic pregnancy.

However, the more risk factors you have (number of cesareans, number of D&Cs, whether you experienced an infection after a cesarean, whether you have a history of Pelvic Inflammatory Disease, prior history of ectopic pregnancy, whether you have had fertility treatment like IVF, whether you smoke, etc.) will also impact your risk.

Personally speaking, I had 2 prior cesareans and never experienced an ectopic pregnancy. Of course, I did not have any other risk factors besides the cesareans, so that might have helped. Either way, I'm glad I had VBACs (Vaginal Birth After Cesarean) with babies #3 and #4 so I did not accrue the risks of additional cesareans. Of course, I might have been fine even if I'd had additional cesareans, but I'm glad to have reduced the likelihood anyhow.

VBAC access may be particularly important for women with multiple risk factors for ectopic pregnancy.

Summary

Ectopic pregnancies are a serious health risk. Although some resolve spontaneously without surgical intervention, those that rupture can have serious consequences, including hemorrhage, infection, and death.

If multiple cesareans are indeed another risk factor for ectopic pregnancy, then the high rate of cesareans and current ban on VBACs in many hospitals has important downstream public health implications.

Ectopic pregnancies are yet another reason why lowering the cesarean rate and improving access to VBACs is such an important goal in improving women's health.


Reference

Am J Perinatol. 2015 Jan 21. [Epub ahead of print] Cesarean Delivery and Risk for Subsequent Ectopic Pregnancy. Bowman ZS1, Smith KR2, Silver RM1. PMID: 25607224

OBJECTIVE: This study aims to examine the risk for subsequent ectopic pregnancy in women with prior cesarean delivery. STUDY DESIGN: Women with a history of at least one cesarean delivery in the state of Utah during 1996 to 2011 were identified and compared with women with vaginal delivery only. The primary outcome was subsequent ectopic pregnancy. Data were analyzed by multivariate logistic regression and stratified by first, second, or third live births. Model covariates included maternal age, ethnicity, marital status, education level, gravidity, and prior ectopic pregnancy. RESULTS: Overall, 260,249 women with at least one live birth were identified. After exclusions, 255,082, 154,930, and 70,228 women had at least one, two, and three prior live births that lead to 531, 199, and 62 subsequent ectopic pregnancies, respectively. Women who had one prior cesarean delivery were not at increased risk for subsequent ectopic pregnancy in relation to women with no prior cesarean delivery. However, women with two of two, two of three, or three of three prior cesareans had increased risk for subsequent ectopic pregnancy with odds ratios (95% confidence interval) of 1.54 (1.06-2.22), 3.50 (1.49-8.24), and 1.99 (1.00-3.98), respectively. CONCLUSION: History of two or three cesarean deliveries is associated with increased risk for subsequent ectopic pregnancy.