What birth defects does misoprostol cause?: A guide to teratogenic effects

October 12, 2025 •

3 min read

Every pregnancy starts with a 3-5% background risk of a major birth defect. While most infants born after first-trimester exposure to misoprostol do not have congenital anomalies, the medication is known to increase the risk of specific birth defects, including Möbius syndrome and limb deformities.

Quick Summary

Misoprostol exposure during early pregnancy, often from failed abortion attempts, can lead to specific congenital malformations. These primarily include vascular disruption defects like Möbius syndrome and various limb abnormalities, though the absolute risk remains relatively low.

Key Points

Möbius Syndrome: Misoprostol exposure is strongly linked to Möbius syndrome, characterized by congenital facial paralysis caused by cranial nerve damage.
Limb Defects: The drug can cause limb reduction defects, such as missing parts of fingers or toes, clubfoot, and arthrogryposis, likely due to vascular damage.
Vascular Disruption Mechanism: The primary cause of these defects is believed to be misoprostol's induction of strong uterine contractions, which disrupt blood flow to the fetus during organ development.
First Trimester Risk: The highest risk of misoprostol-related birth defects occurs when exposure happens during the first trimester, particularly between 5 and 8 weeks gestation.
Relative vs. Absolute Risk: While the absolute risk is low (less than 10 in 1,000 live births after exposure), the relative risk for misoprostol-specific malformations is significantly increased compared to the general population.
Context of Exposure: Many reported cases are linked to unintended continued pregnancy following an unsuccessful abortion attempt using misoprostol.
Precautionary Measures: The FDA labels for misoprostol strictly warn against use in pregnant women for ulcer prevention, emphasizing the need for reliable contraception.

Understanding Misoprostol's Teratogenic Risk

Misoprostol, a synthetic prostaglandin E1 analog, is used for various medical purposes, including preventing NSAID-induced ulcers and obstetric applications like labor induction. However, exposure during pregnancy, particularly in failed abortion attempts, is linked to a pattern of fetal malformations.

Mechanism of action and fetal harm

The prevailing theory for misoprostol's teratogenic effects is vascular disruption. The drug's ability to cause strong uterine contractions, especially in the first trimester, can compress placental and fetal blood vessels. This reduced blood flow can lead to oxygen deprivation and ischemic damage, impacting developing tissues and organs. The timing of this disruption influences which parts of the body are affected. Amniotic band formation due to contractions is another potential mechanism for certain deformities.

Primary Birth Defects Associated with Misoprostol

Specific anomalies have been consistently linked to first-trimester misoprostol exposure.

Möbius syndrome

Möbius syndrome, a rare neurological disorder affecting facial and eye muscles (cranial nerves VI and VII), is frequently reported in misoprostol-exposed infants. The vascular disruption theory suggests that reduced blood flow damages the brainstem nuclei of these nerves during development. This syndrome is often accompanied by other congenital issues, such as limb abnormalities.

Limb reduction defects

Various limb defects, including terminal transverse limb reduction defects (TTLD), are strongly associated with misoprostol. These involve underdeveloped or missing parts of limbs. Other related issues include:

Clubfoot: Foot pointing downward and inward.
Arthrogryposis: Stiff, contracted joints.
Syndactyly: Webbed or fused fingers/toes.

These deformities are also attributed to vascular disruption during limb development.

Other associated malformations

Besides Möbius syndrome and limb defects, other reported abnormalities in misoprostol-exposed infants include orofacial clefts, central nervous system anomalies like hydrocephalus and encephalocele, and cardiac defects.

Risk factors and exposure timeline

Critical window of vulnerability

The timing of exposure is crucial. The highest risk for characteristic misoprostol-related malformations is during the first trimester, specifically between 5 and 8 weeks gestation, a period of rapid organ development. Later exposure (after 12 weeks) carries different risks, such as uterine rupture, but not typically the same teratogenic pattern.

The context of exposure

Many documented cases of misoprostol-related birth defects stem from unsuccessful abortion attempts, particularly where access to safe abortion is limited. Factors like self-administration and dosage variability in these situations make precise risk assessment difficult. For approved uses of misoprostol in women of childbearing age, effective contraception is recommended to prevent exposure.

Comparison of Misoprostol Exposure Outcomes

The risk associated with misoprostol can be understood by comparing outcomes to the general population.


Feature	Misoprostol-Exposed Pregnancies (Early)	General Population Pregnancies
Absolute Risk	Low, but significantly higher for specific defects. Estimated less than 1% for misoprostol-specific malformations.	3-5% chance of any major birth defect.
Primary Mechanism	Vascular disruption, leading to hypoperfusion and ischemia.	Multifactorial; includes genetic factors, environmental factors, and unknown causes.
Characteristic Defects	Möbius syndrome, limb reduction defects (clubfoot, arthrogryposis, etc.), and central nervous system abnormalities.	A wide range of congenital anomalies, with no single, specific pattern.
Effect of Timing	Highest risk for specific malformations in the first trimester (5-8 weeks).	Varies by organ system, with the first trimester being a critical period for many malformations.
Risk Context	Often associated with failed abortion attempts or unintended exposure.	General, unrelated to pharmaceutical exposure.

Conclusion

First-trimester misoprostol exposure is linked to an increased risk of specific birth defects, including Möbius syndrome and limb anomalies. This is thought to be caused by vascular disruption from drug-induced uterine contractions. While the overall absolute risk is low, it is significantly elevated for these particular malformations. Due to these risks, misoprostol is contraindicated in pregnancy for ulcer prevention, and effective contraception is advised for women of childbearing potential using the medication. Women with ongoing pregnancies after misoprostol use should seek medical evaluation for monitoring. More information is available from resources like MotherToBaby.

Frequently Asked Questions

Yes, misoprostol can cause birth defects, particularly if exposure occurs during the first trimester of pregnancy. The risk is specifically linked to certain congenital anomalies like Möbius syndrome and limb reduction defects, though the overall absolute risk is low.

The main mechanism is theorized to be vascular disruption. Misoprostol causes uterine contractions that can lead to reduced blood flow, oxygen deprivation, and vascular damage in the developing fetus during critical periods of organ formation.

The critical period is during the first trimester, specifically between the 5th and 8th week of gestation. This is when the limbs and cranial nerves are most vulnerable to the effects of misoprostol.

The absolute risk of specific malformations from misoprostol is estimated to be relatively low, possibly less than 1% following exposure. However, this is considered a significant increase over the baseline risk found in the general population.

A woman who has used misoprostol during pregnancy and whose pregnancy continues should seek immediate medical consultation. A healthcare provider can offer guidance, perform a comprehensive evaluation, and discuss available monitoring options, such as prenatal ultrasounds.

While the teratogenic risk is highest in the first trimester, misoprostol used later in pregnancy carries other significant risks, including uterine hyperstimulation, uterine rupture, premature delivery, and fetal distress.

Möbius syndrome often involves facial paralysis and the inability to move the eyes from side to side. Other signs can include swallowing difficulties and associated limb defects.