3rd of September 2026
Many across our community living with polyendocrine metabolic ovarian syndrome or PMOS (formerly known as PCOS) have questions around how the condition impacts fertility.
And if that’s you, and you’ve already experienced one (or multiple) losses, it’s so natural to want to understand whether there could be a connection, so you can move your journey forward.
Reliable information is empowering, especially when it comes to something so many of us go through. We spoke with Miss Shirin Khanjani, Co-Founder and Medical Director at Fitzrovia Fertility, to understand the link between PMOS and miscarriage, what bleeding in early pregnancy can mean, and which factors can be addressed before and during fertility treatment.
Located in the heart of London, Fitzrovia Fertility combines cutting-edge reproductive science with a holistic and compassionate approach. Browse our library of expert resources for more authoritative takes on the fertility questions you’re asking.
Now, over to Shirin Khanjani.
Large studies have consistently shown that women with PMOS may have a modestly increased risk of miscarriage.
Much of this increased risk appears to be driven by the metabolic and hormonal changes that can accompany PMOS, including insulin resistance, high levels of male hormones (hyperandrogenism), thyroid dysfunction, obesity and chronic inflammation.
It is important to remember that having PMOS does not mean you will have a miscarriage. It means that some of the underlying factors associated with the condition may increase your risk.
A recent study looked at women with PMOS who had a transfer of a chromosomally normal embryo and compared their miscarriage risk with women without PMOS.
After controlling for embryo quality, the findings showed that women with PMOS had a significantly higher risk of early pregnancy loss than women without PMOS.
This study suggests that the environment hosting the embryo in PMOS can have an impact on the outcome of a pregnancy, even when the embryo is normal.
Looking for PMOS miscarriage rates by week? Unfortunately, there isn’t a single reliable percentage we can lean on.
Miscarriage risk changes throughout early pregnancy and is influenced by several factors, including age, previous pregnancy history and the individual circumstances of the pregnancy.
Generally speaking, metformin may reduce the risk of early miscarriage, but more studies are needed.
Recent research by Tommy’s National Centre for Miscarriage Research indicates that continuing metformin through the first trimester of pregnancy may reduce the risk of early miscarriage in women with PMOS.
However, this is just one treatment approach, and metformin is not appropriate for everyone with PMOS. The evidence is still developing, and decisions about whether to start or continue metformin during pregnancy should be made with your fertility or maternity team.
The research is particularly relevant because we currently use different approaches to metformin in pregnancy, depending on how the condition is impacting you.
Some patients will stop it after a positive pregnancy test, while others continue treatment into pregnancy.
Very light bleeding or spotting in early pregnancy can happen, and does not always mean that you’re having a miscarriage.
However, any bleeding during early pregnancy should always be discussed with a healthcare professional, particularly if it is accompanied by pain, heavier bleeding or other symptoms.
At Fitzrovia Fertility, we’d recommend an assessment, blood tests and/or an ultrasound depending on how far along the pregnancy is and your symptoms.
Yes, PMOS can cause random, unpredictable or breakthrough bleeding between periods.
This happens because PMOS can disrupt ovulation and the normal hormonal pattern that controls the menstrual cycle. If you’re not ovulating regularly, the womb lining can build up and shed unpredictably, resulting in irregular bleeding.
During pregnancy, however, bleeding should be assessed separately – even if you have a history of irregular bleeding because of PMOS.
The encouraging news is that most of these factors associated with PMOS are modifiable.
So when I have a patient with PMOS here at Fitzrovia Fertility, it is not just that diagnosis that is important; it is about the metabolic impact of that diagnosis on your health.
I’d factor in: are we dealing with insulin resistance? Are you struggling with your weight? Are we dealing with high levels of male hormones? Is there inflammation in the body?
Understanding these factors helps us get to the root of what may be affecting your fertility and identify where we can make meaningful changes, which we can then tackle individually. Our goal isn’t simply to get you pregnant, but to support you to have a healthy pregnancy and eventually take your baby home with you.
Can PMOS cause miscarriage? A fertility specialist explains was originally published on The Ribbon Box, and is shared here with permission.
Table of Contents