Endometriosis makes both conceiving and carrying a pregnancy more challenging, though most women with the condition do go on to have healthy pregnancies. The effects span the entire journey: from reduced fertility and a modestly higher miscarriage rate to increased risks of preterm birth and cesarean delivery. Understanding these risks helps you know what to watch for and what your care team will be monitoring.
Why Endometriosis Makes It Harder to Conceive
The link between endometriosis and infertility involves several overlapping problems. Endometrial tissue growing outside the uterus triggers chronic inflammation, which disrupts the delicate hormonal balance needed for an egg to mature properly. The fluid surrounding developing eggs contains immune cells and inflammatory molecules that, in women with endometriosis, can interfere with egg quality before ovulation even occurs.
Adhesions, the bands of scar tissue that form around endometrial implants, can physically distort the pelvic anatomy. Fallopian tubes may become blocked or kinked, preventing the egg and sperm from meeting. Ovarian endometriomas (cysts filled with old blood) can reduce the number of healthy eggs available, lowering ovarian reserve over time.
Even when an egg is fertilized, implantation can fail. The uterine lining in women with endometriosis shows reduced levels of key proteins that help an embryo attach and burrow in. Immune cells in the uterus, particularly a type of natural killer cell, behave abnormally, and the inflammation alters the lining’s receptivity during the narrow window when implantation is possible. These factors together explain why many women with endometriosis need fertility treatment, though the severity varies widely from person to person.
Miscarriage Risk
Women with endometriosis face a modestly higher chance of pregnancy loss. A large nationwide study found that about 18.9% of ever-pregnant women with endometriosis experienced at least one miscarriage, compared to 17.3% of women without it. That gap may sound small, but the risk climbs with recurrent losses: women with endometriosis were 75% more likely to have two pregnancy losses and more than 2.5 times as likely to have three or more, after accounting for the number of pregnancies.
The underlying inflammation and impaired uterine lining receptivity that make implantation difficult likely contribute to early losses as well. If you have endometriosis and have experienced recurrent miscarriages, your provider may recommend closer monitoring in early pregnancy or additional hormonal support.
Preterm Birth and Placental Problems
Once pregnancy is established, endometriosis raises the odds of delivering early. A large multicenter study found that 11.1% of women with endometriosis delivered before 37 weeks, compared to 7.7% of women without it. That translates to roughly a 40% higher adjusted risk. For very early preterm birth (before 33 weeks), the risk was about 53% higher.
Placenta previa, where the placenta covers the cervix, also occurs more frequently in women with endometriosis. This association held regardless of whether conception happened naturally or through fertility treatment, suggesting it is related to the disease itself rather than to assisted reproduction. Preeclampsia and postpartum hemorrhage were also elevated in the endometriosis group, and babies were more likely to be smaller for their gestational age.
How Adhesions Cause Problems During Pregnancy
As the uterus expands, pre-existing adhesions from endometriosis or from prior surgeries to treat it can create traction on surrounding organs. Scar tissue that was painless before pregnancy may start pulling on the bladder or bowel as the uterus grows, causing pain or, in rare cases, bowel obstruction or perforation. These complications are not unique to endometriosis. Any pelvic or abdominal surgery, including a previous cesarean section, can leave adhesions that behave the same way. But women with endometriosis are more likely to have both disease-related and surgical adhesions, compounding the risk.
Endometriomas Can Mimic Cancer on Imaging
If you have an ovarian endometrioma going into pregnancy, expect it to change. About 74% of endometriomas shrink during pregnancy, but 58% undergo a process called decidualization, typically first noticeable around 17 weeks. The cyst develops solid, blood-vessel-rich components that on ultrasound look strikingly similar to borderline or invasive ovarian tumors.
This overlap in appearance is a well-recognized source of misdiagnosis. The critical difference is that decidualized endometriomas regress after delivery. The solid components disappear, and a follow-up ultrasound after birth confirms the cyst is benign. If you already know you have an endometrioma and your provider flags a concerning-looking ovarian mass during pregnancy, this transformation is the most likely explanation. Unnecessary surgery can often be avoided by monitoring the mass and rescanning postpartum.
Higher Cesarean Section Rates
Women with endometriosis are significantly more likely to deliver by cesarean section. One study found nearly five times the odds of a C-section compared to women without the condition. Several factors drive this: adhesions can make labor progression unpredictable, placenta previa may require a planned surgical delivery, and prior pelvic surgeries increase the complexity. In some cases, the decision is precautionary, driven by the provider’s awareness of potential adhesion-related complications during a vaginal delivery.
Symptoms After Delivery
Pregnancy itself often provides temporary relief from endometriosis symptoms because menstrual cycles stop and progesterone levels remain high. After delivery, symptoms typically return once menstruation resumes. Breastfeeding can delay that return. Research shows that the risk of endometriosis-related problems drops by about 8% for every three months of breastfeeding after each pregnancy. Exclusive breastfeeding, with no formula, solid food, or water supplementation, offers an even stronger effect: a 14% reduction for every additional three months. Women who exclusively breastfed for a cumulative total of at least 18 months across their reproductive years were nearly 30% less likely to have ongoing endometriosis issues.
The protective effect likely relates to the suppression of menstrual cycles during breastfeeding, which limits the hormonal stimulation that drives endometrial tissue growth. This does not mean breastfeeding cures the disease, but it can meaningfully extend the symptom-free window after birth.