Can poor sperm health contribute to miscarriage?

Miscarriages have often been attributed to issues involving the mother or pregnant person. However, recent research has suggested that paternal factors, such as age and sperm health, may play a role in miscarriage, including recurrent miscarriage. Let’s take a look at risk factors for miscarriages, whether your sperm can cause a miscarriage, and what to do if you’ve experienced multiple miscarriages.

Takeaways:

• A pregnancy that is lost before 20 weeks is called a miscarriage. Recurrent miscarriage is defined as two or more consecutive lost pregnancies.
• Approximately half of miscarriages result from chromosomal abnormalities in the embryo. Research indicates that poor sperm quality, particularly sperm with damaged DNA, is linked to miscarriage and recurrent miscarriage.
• If you’ve experienced multiple miscarriages, sperm DNA fragmentation testing may help you understand the cause. Most people who’ve had multiple miscarriages can still give birth to a healthy child.

What is a miscarriage?

A miscarriage, also known as a spontaneous abortion, occurs when a pregnancy is lost unexpectedly prior to 20 weeks. (At or after 20 weeks, the loss of a baby is known as a stillbirth.) According to the National Institutes of Health, the majority of miscarriages occur early in the pregnancy, possibly before the person even realizes they’re pregnant.

Symptoms may include cramping and vaginal bleeding. In some instances, medication or surgery may be used to clear remaining tissue from the uterus. Miscarriages can be emotionally difficult for both parents, and those who have experienced a miscarriage should be encouraged to seek therapy or grief counseling to help them process their loss.

What is recurrent miscarriage?

Recurrent miscarriage, or recurrent pregnancy loss (RPL), is defined as two or more failed pregnancies in a row. There are two types of recurrent miscarriage: primary RPL, in which the patient has never given birth to a live child, and secondary recurrent pregnancy loss, in which the patient has previously birthed a live baby.

How common is miscarriage and recurrent miscarriage?

Estimates vary, but miscarriages occur in around 26% (possibly more) of all pregnancies. About 80% of these happen during the first trimester (the first 12 weeks of the pregnancy), with a lower risk of miscarriage during the remaining two phases of the pregnancy. While there’s less information on second trimester miscarriages, the prevalence between 15 and 21 weeks appears to be around 0.4% of all pregnancies.

Research indicates that the risk of miscarriage increases after prior miscarriages. After one miscarriage, the chance of a future miscarriage is around 20%; after two miscarriages in a row, the future risk is 28%; and after three consecutive miscarriages, the risk of having another is 43%.

Still, recurrent miscarriage is uncommon, affecting approximately 2% of pregnant people. Around 1% will lose three consecutive pregnancies.

Possible causes of miscarriage

Around half of miscarriages are likely a result of chromosomal abnormalities in the embryo. Aneuploidy, a condition in which an embryo has an extra or a missing chromosome, is present in 5 to 10% of pregnancies and usually results in a miscarriage.

The risk of chromosomal abnormalities increases with the mother’s age, with one study finding the risk to be 4–7 times higher in mothers over age 35 compared to those age 25–29. The miscarriage rate increases similarly with age; there’s an 8.9% risk of pregnancy loss in women 20–30 years old, compared to a 74.7% risk in women over 40.

Chromosomal abnormalities in one or both partners are associated with recurrent miscarriages. However, in up to half of recurrent miscarriages, the reason is not known.

Other risk factors associated with an increased chance of miscarriage include:

• excessive alcohol use
• smoking
• drug use
• obesity
• chronic conditions including diabetes, celiac disease, and thyroid disorders
• infections such as malaria and syphilis
• lead exposure

It’s important to note, however, that most miscarriages cannot be pinned to a specific behavior or lifestyle factor. Miscarriage is a natural and, in most cases, unpreventable phenomenon, and loss is rarely the “fault” of the pregnant person.

Can poor sperm health contribute to miscarriage?

Miscarriages are not only affected by factors involving the mother; there may be paternal causes, too.

Sperm DNA damage and miscarriage

The primary job of sperm is to carry DNA to combine with the egg, creating a unique genetic code for the offspring that incorporates genes from both parents. The DNA carried by sperm is fragile; it can be damaged or broken, a condition known as “sperm DNA fragmentation.”

Research indicates that sperm with DNA damage can, in some instances, still fertilize an egg. However, this may lead to impaired embryo quality and greater chances of miscarriage. Sperm DNA fragmentation may be caused by:

• cell death during sperm production
• free radical damage
• cancer treatments like chemotherapy
• environmental or lifestyle factors, such as smoking

A 2012 meta-analysis linked sperm DNA fragmentation to miscarriage, finding that people with increased amounts of damaged sperm had higher miscarriage rates than those with low DNA damage. A study from 2018 also showed lower sperm motility (the ability of sperm to move properly), increased sperm DNA fragmentation, and more free radicals in the group of men whose partners had had a miscarriage.

Sperm DNA damage and recurrent miscarriage

Research into the link between sperm DNA damage and recurrent miscarriage is mixed. One recent study found that men whose partners experienced recurrent pregnancy loss had higher average sperm DNA fragmentation than the control group. These men also had lower sperm motility and decreased normal morphology (the size and shape of sperm). The study suggested that reproductive assessments (semen analysis and sperm DNA fragmentation testing) of male partners may be useful in cases of recurrent miscarriage. 

A study from 2017 also found impaired sperm DNA in men from couples experiencing recurrent pregnancy loss. The group experiencing RPL had significantly higher levels of sperm DNA fragmentation than fertile men — levels comparable to those of infertile men. Still, the study noted that sperm DNA fragmentation still can’t be used to predict the risk of recurrent miscarriage.

On the other hand, one 2015 study found little difference in sperm DNA fragmentation in partners of women with recurrent miscarriage compared to controls. More research should be done to confirm the impact of sperm DNA fragmentation and the ability of sperm DNA testing to predict pregnancy loss. Still, multiple studies have associated sperm DNA damage with both single and recurrent miscarriages.

What should we do if we’ve experienced multiple miscarriages?

If you or your partner have two or more consecutive miscarriages, a specialist — such as a maternal-fetal medicine physician or a reproductive endocrinologist — can help determine the cause and potential treatment. An evaluation may include:

• collecting your and your partner’s medical history, including any history of miscarriages in your family and lifestyle factors that may affect miscarriage risk
• testing for medical conditions that may increase the risk of miscarriage, including genetic karyotype testing for both partners to look for chromosomal abnormalities
• scanning the uterus and pelvis with ultrasound to check for abnormalities

You may also want to do sperm DNA fragmentation testing to understand if sperm quality might be contributing to your recurrent miscarriage. Legacy offers sperm DNA fragmentation analysis that you can easily complete at home.

If you or your partner has had a miscarriage, be comforted by the fact that your chances of birthing a healthy baby are still very high. Research shows that the majority of people who have experienced miscarriage, even recurrently, will go on to have a child.