Only starting to check after 3 miscarriages? Data from 370,000 women — here’s what it really reminds us of

Getting pregnant is one thing—but carrying to term is another. For women who have experienced miscarriage or pregnancy loss, the hardest part is often not the failure itself, but never finding a clear "why." After a first miscarriage, many women hear the same reassurance: "It might just be bad luck. Try again."

But when it happens a second or third time, "bad luck" may no longer be the simplest explanation.

A large cohort study from Denmark, covering 366,539 women, points to an important connection worth attention: there is a clear association between a history of miscarriage and endocrine disorders in women. And as the number of miscarriages increases, this association becomes even more pronounced.

For women trying to conceive naturally, preparing for IVF, or considering third-generation IVF services in Thailand, the most important takeaway from this data is not just the number "81%," but rather this: before the next pregnancy or assisted reproduction cycle, are there issues we may have overlooked that deserve to be checked in advance?

1. Long-Term Data from 360,000+ Women: More Miscarriages, Greater Reason to Look at Endocrine Health

This study included Danish women born between 1977 and 1993 and analyzed their long-term medical and prescription records. Among women with at least one recorded pregnancy, 56,618—approximately 15.4%—had been diagnosed with some form of endocrine disorder.

These included: hypothyroidism, hyperthyroidism, polycystic ovary syndrome (PCOS), type 1 diabetes, type 2 diabetes, and gestational diabetes.

The researchers then grouped women according to how many miscarriages they had experienced. The results revealed a trend that deserves serious attention: women who had experienced 1 miscarriage had an approximately 15% increased risk of an endocrine disorder diagnosis; those with 2 miscarriages had an approximately 30% increase; and for women with 3 or more miscarriages, this figure reached 81%.

An important clarification: "An 81% increase" does not mean that 81% of women who have had three pregnancy losses will develop an endocrine disorder.

It refers to the increased relative risk observed in the study compared with women who had no history of miscarriage. At the same time, this type of observational study reveals a statistical association between the two—it should not be interpreted as "endocrine disorders definitely cause pregnancy loss."

But for those who have experienced recurrent pregnancy loss, this still sends a very important signal: beyond looking at the embryo alone, a woman's own endocrine and metabolic environment deserves systematic evaluation.

2. Why Can't We Focus Only on "Is the Embryo Healthy?"

After a pregnancy loss, many people's first thought is: "Was it a chromosomal problem in the embryo?"

Chromosomal abnormalities are indeed one of the major causes of early miscarriage. But by the same logic, this also means: not all miscarriages can be explained by embryonic chromosomal abnormalities alone. This is especially true for women who have experienced multiple losses, whose embryo testing found no obvious problems, or who are already in an IVF cycle. The scope of evaluation often cannot stop at the embryo alone.

A woman's own thyroid function, glucose metabolism, insulin status, PCOS, hormone levels, and other related factors may all be part of what a doctor needs to assess when evaluating a pregnancy. This is precisely why, in the overseas fertility consultations and cross-border reproductive services that Global New Life handles daily, we always emphasize: assisted reproduction does not end with simply obtaining an embryo—it requires evaluating the embryo, the maternal environment, and past pregnancy history together as a whole.

3. After Recurrent Pregnancy Loss, Pay Particular Attention to These 3 Categories of Issues

This Danish study further analyzed a range of endocrine disorders, and several areas deserve particular attention.

1. Thyroid Dysfunction

The thyroid may seem far removed from the uterus, but it actually participates in metabolic regulation, reproductive endocrinology, and various physiological processes related to pregnancy.

Study data shows: among women who experienced 3 or more miscarriages, the prevalence of hypothyroidism was approximately 6.8%; by comparison, the control group was approximately 3.6%. For anyone with a history of pregnancy loss, thyroid function is therefore a very important item for doctors to assess. This is especially true if thyroid function has never been systematically checked, or if there is a relevant family history—it is not advisable to dismiss it simply because "I don't have obvious symptoms day to day."

2. Polycystic Ovary Syndrome (PCOS)

PCOS is a term familiar to many women preparing for IVF. It is not just about "irregular periods" or "having more follicles." PCOS can also involve ovulatory dysfunction, changes in androgen levels, insulin resistance, and other metabolic issues.

The study found that among women who had experienced 3 or more miscarriages, the prevalence of PCOS was approximately 6.1%, compared with approximately 2.6% in the control group.

So if you have already been diagnosed with PCOS and are preparing for natural conception or third-generation IVF in Thailand, the more important thing is not to feel anxious at the word "polycystic," but to understand: where exactly do my ovulation, hormone, and metabolic status stand?

Two people can both have PCOS yet present very differently, so ultimately the treatment plan needs to be developed by a physician based on individual test results.

3. Blood Sugar and Metabolic Issues

The study also observed a significant association between type 2 diabetes, gestational diabetes, and miscarriage. This is also an issue that young women tend to overlook. Some might think: "I'm young, I'm not overweight—diabetes is far from me." But reproductive medicine is not only concerned with whether someone meets the diagnostic criteria for "diabetes."

If there are abnormalities in blood glucose metabolism, insulin resistance, or related conditions, it is also worth having a physician evaluate further. This is especially relevant for women with PCOS, because of the complex interplay between reproductive endocrinology and metabolism. Before entering an IVF cycle, doctors typically do not look only at AMH and antral follicle count.

4. An Easily Overlooked Detail: When Was the Problem First Identified?

The study also produced a very thought-provoking finding. The researchers divided women into two groups: those who had been diagnosed with an endocrine disorder before their first pregnancy, and those who were not identified until after their first pregnancy.

The results showed: women who were diagnosed with an endocrine disorder only after their first pregnancy had an approximately 24% higher risk of miscarriage in that first pregnancy; for women diagnosed before pregnancy, the corresponding increase was approximately 11%.

This result should not be oversimplified as: "If you treat it in advance, you can definitely reduce your miscarriage risk by 13%." The study itself cannot directly prove such a causal relationship. But it does remind us that some endocrine issues may have been present before a first pregnancy—just never previously detected. This is the real value of preconception assessment.

It is not about "the more tests, the better." It is about identifying clinically meaningful issues as early as possible before entering pregnancy.

5. You May Not Be Sick—But Don't Forget to Ask Your Parents and Sisters

There is another factor that is easily overlooked: family history.

The study found that even when a woman herself had not been diagnosed with a related endocrine disorder, if a first-degree relative had a relevant medical history, her miscarriage risk still showed a certain degree of increase.

The data showed: women whose parents had an endocrine disorder had an approximately 7% increased risk; women whose sisters had an endocrine disorder had an approximately 8% increased risk.

This suggests that when preparing for pregnancy, in addition to asking yourself "Do I have any conditions?", it is also worth looking into: Does my mother have diabetes? Does my father have notable blood sugar issues? Do my sisters have thyroid conditions? Have any women in my family had PCOS or similar conditions?

This information may seem unrelated to your own pregnancy at first glance, but it can help doctors build a more complete picture of your familial risk background.

6. After a Pregnancy Loss, What Can You Focus On Before the Next Attempt?

What truly matters is not becoming anxious upon seeing "81%," but knowing how to approach the next step more scientifically.

First: Don't Look for a Single Cause

Pregnancy loss is often multifactorial. Embryonic chromosomes, age, uterine environment, endocrine function, metabolism, immunity, and other medical factors may all need to be evaluated based on individual circumstances. After one or even multiple losses, it is not advisable to jump to conclusions like "It must be poor egg quality" or "It must be caused by my hormones." What really matters is narrowing down the possibilities based on your history of pregnancies and test results.

Second: Include Endocrine and Metabolic Assessment

If you have had a miscarriage of unknown cause—especially recurrent losses—consider discussing with your doctor whether further evaluation is needed for: thyroid function, blood glucose and HbA1c, relevant reproductive hormones, and other tests based on your individual situation.

The specific tests, their timing, and whether further intervention is needed should be determined by a physician based on your personal circumstances—not by working through a generic "checklist" found online.

Third: If a Problem Is Already Known, Don't Delay Until After Pregnancy

If you already know before conceiving that you have a thyroid condition, PCOS, diabetes, or another metabolic issue, the more sensible approach is: undergo proper evaluation and management first, and let your doctor determine when your body is ready for pregnancy or an assisted reproduction cycle.

For those planning to travel to Thailand for third-generation IVF, this point deserves extra attention in advance. Cross-border medical care involves multiple stages: medical records, physician consultations, ovarian stimulation, egg retrieval, embryo culture, and the subsequent transfer.

If you only discover upon arrival in Thailand that your baseline indicators need adjustment, it could not only affect the original plan but also add time and travel costs.

For this reason, when Global New Life provides overseas medical accompaniment and process coordination services, we recommend that clients organize their past medical records, test reports, and pregnancy history in advance, and then have the physicians at the medical institution make their assessment.

7. Third-Generation IVF Can Screen Embryos—But It Does Not Solve Every Cause of Pregnancy Loss

This is a common misconception among those preparing for overseas fertility treatment. If third-generation IVF can perform genetic testing on embryos, wouldn't selecting a healthy embryo mean pregnancy loss can no longer happen? The answer is not that simple. Take PGT-A, for example: it is primarily used to assess chromosomal number abnormalities in embryos.

But: the embryo is only one end of the pregnancy—the mother is the other. Even if certain risks at the embryonic level are screened out, a woman's own uterine conditions, endocrine status, metabolic profile, and other medical factors can still influence the outcome of a pregnancy. A truly scientific preparation process for third-generation IVF in Thailand therefore should not be only: ovarian stimulation → egg retrieval → blastocyst culture → PGT → transfer. It should also include: past pregnancy history → baseline testing → individual risk assessment → embryo status → maternal health → transfer preparation. That is a more complete approach.

8. Why Can Some People Have Many Tests Done and Still Find No Answers?

This is one of the most frustrating realities of reproductive medicine: not every pregnancy loss will ultimately have one single, identifiable cause. Sometimes it is an embryonic factor; sometimes it may be related to the mother's condition; and sometimes multiple factors work together. For those who have experienced repeated failures, the most important thing is not to keep searching for one "single answer" that explains everything, but to address each identifiable and manageable risk factor one by one.

This is also why, in the process of cross-border family building and overseas fertility treatment, a complete medical journey should not simply be "helping a client book an appointment at a hospital."

From organizing medical records upfront, matching with the right physician, and communicating about which tests are needed, to translation support, logistics coordination, and medical accompaniment after arriving in Thailand—every step can affect the efficiency of the entire cycle.

In Closing: What Truly Deserves Attention Is Not the Number "81%"

This long-term Danish study covering more than 360,000 women gives us something far more valuable than a number designed to provoke anxiety. It offers a very simple reminder: after a miscarriage, in addition to asking "what happened with the embryo," we should also look at whether there are overlooked issues within our own bodies.

Thyroid function, PCOS, blood sugar, and other endocrine and metabolic conditions may seem far removed from pregnancy—but studies show they have a meaningful association with a history of miscarriage. Especially for those who have experienced recurrent pregnancy loss, are preparing to try again, or are considering IVF or third-generation IVF in Thailand: don't let one failure send you into excessive anxiety, but also don't let "let's just try again" cause you to skip the evaluations that should be done. First, clarify what has happened in the past, identify any discoverable issues as early as possible, and then plan the next steps together with a qualified physician.

For families planning assisted reproduction in Thailand, Global New Life provides services including organizing medical records in advance, hospital and physician appointment scheduling, logistics coordination, translation support, and overseas medical accompaniment—helping make the complex journey of cross-border fertility treatment clearer and more manageable.

Every time you begin again should not be another gamble on luck—it should be a step forward with greater understanding and better preparation than the last.