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Secondary Infertility, Common Causes, and the Connection with Postnatal Depletion

Updated: Jan 31, 2023

Secondary infertility is defined as the inability to become pregnant or carry a pregnancy to a live birth following a previous successful pregnancy. Did you know that it is more common than primary infertility?

Some interesting statistics from a Health Masters Live masterclass I attended on unexplained infertility with Australian Naturopath Angela Hywood confirmed:

1.7% of women suffer from primary infertility

10.5% of women with at least one live birth suffer from secondary infertility.

Secondary infertility can be a frustrating journey especially if you didn’t have any problems conceiving your first child. You may be wondering what has happened to you and whether the birth of your first child has broken you.

This was me. My first son was born in 2008 after a healthy problem free pregnancy. He was conceived fairly easily. His birth though was not so easy. I will share a little about this later.

Despite deciding to try again in early 2009 when he was just over 12 months old, it took me nearly 10 years to finally have a second child. My beautiful baby girl was born in early 2019.

The guilt and the blame

Even though secondary infertility is much more common than primary fertility, in society it is often not seen to be as big of an issue as you already have a child. We are often told that we should be grateful that we have one child as many people in the world aren’t even able to have one.

While I did feel grateful and totally blessed to have a son, I also felt angry at myself for not being able to get pregnant, I blamed myself for being broken and felt guilty that I was unable to give my son a sibling to play with. He would often ask in his preschool and primary years “why don’t I have a brother or sister?” or “when will I be getting a brother or sister?” I felt so bad for him, especially when all of his friends one by one started getting their own brothers and sisters, and some even went on to have a second sibling as well.

It was tough for me too when my son was young as I was also in a mother’s group where the talk was all about babies and every single one of them went on to have a second child. With secondary infertility, you are faced with the pain and reminders daily as you are unable to hide from or block out babies and pregnancy because of the life stage you are already in with a toddler or preschooler. Soon I was the only one out of absolutely everyone I knew in my circle who didn’t at that time have a second or third child.

What are the causes?

There can be many causes of secondary infertility and in many cases, a cause may not be found and you are categorised as unexplained. These are some of the common causes which are investigated by your doctor and fertility clinic:

Egg quality and quantity

The quality and quantity of your egg supply are related to age and many women are having children later in life. If you are over the age of 35 your chances of conceiving each cycle are naturally on the decline.

Structural issues

This could be scar tissue or damaged or blocked fallopian tubes. If any of these issues are suspected you will most likely have a scan at the hospital where they will filter a blue dye through your fallopian tubes to check for blockages.


You may have always had some mild endometriosis which didn’t affect your ability to have a first child but may have worsened over time and is a problem now. Endometriosis is common and is where uterine tissue grows outside the uterus in locations such as the ovaries, fallopian tubes, or other organs such as the bowel. Depending on the severity of the endometriosis the inflammation and scar tissue can lead to issues with egg quality, ovulation, and implantation.


Uterine conditions such as fibroids may be present and are connected to estrogen dominance and are common in women over the age of 35. Fibroids can occur in 7 out of 10 women by the time they reach 50.

Hormone Imbalances

Common hormone imbalances that can affect secondary infertility are estrogen dominance, low progesterone, low or excess androgens as well as issues with low or excess cortisol from your adrenal glands. These issues may not always be picked up by the standard day 5 or 21 blood test you have with your doctor.

We are very fortunate these days to be able to investigate hormones on a deeper level with a dried urine test called the DUTCH test. The DUTCH test offers a comprehensive hormone test that includes hormone metabolites, organic acids, and methylation and oxidative stress markers. It is especially useful for investigating adrenal function, estrogen and progesterone balance, androgen deficiency or excess, and whether the metabolism of hormones is sluggish or overactive. I can organise a DUTCH test for my clients and I am trained to be able to interpret the results, which can seem quite complex when you first look at them as there is so much valuable information. The DUTCH test is a great way to investigate what is really happening with your hormones as it not only provides information on free hormones but downstream metabolites as well which tells us how the hormones are functioning.

Thyroid health

It is quite common to develop thyroid issues in the postpartum period after having your first child and for many the changes in metabolism are permanent. I will talk more about this later in this blog.

Autoimmune conditions

In some cases, pregnancy can trigger the onset of many autoimmune conditions, examples of these might be Antiphospholipid Syndrome, Lupus, Hashimoto's Thyroiditis, Graves Disease, and Rheumatoid Arthritis. `Research has shown that autoimmune diseases have a significant prevalence within the female population and a considerable portion of women who are mothers. 44.3% of women who develop an autoimmune disease have onset after the first year of pregnancy (1)

There are many theories why this occurs such as fetal cells remaining in the mother postpartum and triggering an autoimmune response as well as the stress and demands of pregnancy, hormone imbalances, and cesarean delivery (which increases the risk).

There are more than 70 registered autoimmune conditions and many of these can go unnoticed and undiagnosed. In the case of recurring miscarriages, your doctor may test you for antinuclear antibodies (ANA) to see if you have elevated autoantibodies attacking your body tissues. It is also important to also get screened for antiphospholipid antibodies (to see if blood clotting is an issue), Coeliac Disease, and autoimmune thyroid disease (Hashimoto’s or Graves).


An infection of the urinary and reproductive tract called ureaplasma may be problematic with severe cases of endometriosis and recurring pregnancy loss. Ureaplasma is microscopic bacteria that colonise the urinary and reproductive tract and are for most people harmless and asymptomatic. An overgrowth though can cause inflammation of the endometrial lining and may require a course of antibiotics to resolve.

Polycystic ovary syndrome (PCOS)

PCOS is a common syndrome that can affect fertility as women with PCOS may not ovulate and may have irregular periods. Females with PCOS may have insulin resistance, high levels of androgens, excess hair growth, acne, and weight gain.

Lifestyle factors

Excessive weight gain in both males and females as well as smoking, alcohol use, and level of exercise.

Male factor

In men, common reasons are a low sperm count, a varicocele, and other sperm abnormalities.

Unexplained Secondary Infertility

If after the standard blood tests and scans with your fertility clinic nothing obvious is identified, which was the case with me, you will be labeled as “unexplained” and usually advised to go on the waiting list for IVF. Around 1 in 5 cases of secondary infertility are identified as unexplained which basically means your fertility doctor has found no obvious reason that you are unable to conceive a second child. This is not the end of the road, though because there is a whole world of further options to explore in the world of functional medicine.

Postnatal depletion

I believe postnatal depletion is a major cause of unexplained secondary infertility. Mothers are so depleted of nutrients and energy from pregnancy and breastfeeding that they are just not physically capable of conceiving again until they build themselves back up again.

Having a baby and breastfeeding is hugely demanding and can change a woman’s body forever. During pregnancy and breastfeeding the baby will strip all the nutrients it needs to grow from the mother’s nutrient stores leaving her at risk of nutritional deficiencies such as iron, calcium, vitamin B12, folate, and zinc. This nutrient depletion will impact the body’s ability to function normally and as a result, there can be changes in metabolism and hormone health. The adrenal glands in particular can become fatigued from the demands of motherhood and sleepless nights, which then impacts on the thyroid and progesterone levels. Many mothers may also be recovering from the emotional trauma of difficult birth and maybe (like I had) excessive blood loss which resulted in low levels of iron and B12 which took a while to return to healthy levels.

So, when you try and get pregnant again in this state, your body is like NO WAY!

According to Functional Medicine Doctor Oscar Serralach, Author of the book The Postnatal Depletion Cure, Postnatal depletion can affect mothers from birth until the child is 7 years of age and possibly longer. Typical symptoms of postnatal depletion are fatigue, exhaustion, brain fog, hypervigilance, loss of self-esteem, overwhelm, and a loss of libido. (2)

I believe that postnatal depletion was a huge contributing factor to my secondary infertility journey.

My story

My first son was conceived fairly easily after 5 months of trying and my pregnancy was relatively easy with no major complications. Despite my problem free pregnancy, my son’s birth was far from easy I won’t go into all the details but I can say it was a painful labour that went on for over 24 hours. He was a big baby, there were some complications, and he was finally helped out with episiotomy and ventouse as he was stuck and unable to progress for a long time.

Immediately after I gave birth to my son I has a massive postpartum hemorrhage, which required urgent medical attention at the time, an experience that was very scary. I remember the doctor, nurses, and midwife all rushing around looking a little panicky pressing on my stomach to get the placenta out and there was an awful lot of blood.

My health deteriorated the next day and doctors informed me that because my hemoglobin (protein in your red blood cells that carries oxygen throughout your body) was so low I would need an immediate blood transfusion. It was about 92 g/L when it should be no lower than 114 g/L. The normal reference range for females is 120 g/L - 160 g/L. I didn’t like the sound of a blood transfusion however, after a chat with the doctor, I realised that I would not physically have the energy to able to look after my child unless I have a blood transfusion. So I did.

My challenges didn’t end there. Maybe due to the blood transfusion, my milk supply didn’t come through and after 10 days I had to take a prescription anti-nausea drug to kick start my prolactin hormone production which is the hormone that starts off the breastfeeding process. I also had to spend a lot of time expressing and topping up with formula milk which was very stressful and meant that I didn’t spend much time sleeping.

Everything really started to take its toll in the first week after my son was born and to make matters worse I couldn’t sleep! Sleep when your baby sleeps they would say, but every time I tried to sleep my mind was wide awake. I remember being so tired that I fell asleep while sitting up and talking to the hospital canteen lady who had come to take my food order. I literally didn’t sleep for a whole week!

Looking back, I think about the huge emotional and physical toll of my son’s labour and the weeks that followed and how this would have affected my health. This is in addition to the ongoing demands of 14 months of breastfeeding when it was eventually established and 7 months of my son waking multiple times during the night.

When my son was just over 12 months, we decided to try for another baby. I didn’t feel totally ready at first and hoped that it would take several months like last time. A few weeks later I realised that my period was late and so I took a pregnancy test at what would have been nearly 5 weeks. I was shocked to see it was a faint positive and thought I would take another test the next day to make sure before saying anything to anyone only to find that my period had arrived. This was likely my first chemical pregnancy.


Even though I wasn’t ready to try again the realisation that I had just experienced an early pregnancy loss was very upsetting. It made me realise that I did really want to get pregnant after all and I was determined to get pregnant again as soon as possible.

As I had just started studying nutrition at the time, I spent time researching early pregnancy losses to try and understand why this might have happened to me. My doctor decided to test my iron levels as she was wondering if they were still low after my postpartum hemorrhage where I lost nearly a litre of blood. A couple of days after the blood test I received a phone call from the nurse to say that my blood tests were normal and no further action was required. I asked to see a copy of my blood test results and was shocked to see that my “normal” Ferritin was 22 when the reference range was at that time 20 -200 ng/mL. Ferritin is a blood protein that contains iron and testing ferritin shows how much iron your body stores. I couldn’t believe I was told my iron was normal when clearly it was just above the lowest reference range indicating my iron stores were very low. This would explain why I felt like a zombie most of the time. I knew I would be tired with the sleep deprivation of having a new baby, but I didn’t have to feel so tired. Once I started taking iron my energy levels started to improve gradually.

low iron can be problematic if you are trying to conceive as it not only increases the risk of miscarriage due to a lack of blood flow and oxygen to the uterus but also plays an important part in a healthy thyroid function as it is one of the nutrients that is involved in the conversion of T4 (thyroxine the inactive thyroid hormone), to T3 (triiodothyronine the active thyroid hormone).

If your ferritin is low just starting taking an iron supplement isn’t going to magically fix the problem as iron can be slow to absorb and can take at least 6 months to get your iron stores up to a healthy level, which is a ferritin range of at least 70 ng/mL. This is why it is critically important to test iron levels as part of a 3 – 4-month preconception care programme, especially for women who are looking to conceive a second child as low iron could be a probability.


Zinc is another mineral commonly deficient in mothers postpartum and if not corrected can impact future fertility. This is because zinc is an important mineral for fertility, is involved in reproduction hormone regulation, immune function, and is important for thyroid function as it is involved in the conversion of T4 to T3. Zinc is an antagonist to the mineral copper so when one is elevated the other can become deficient. Copper often becomes elevated during pregnancy and high copper levels postpartum can lead to zinc deficiency. This is one of the common patterns seen with postnatal depression and supplementing with Zinc can be helpful. As well as postnatal depression, white spots on the fingernails, low appetite, and an altered sense of taste and smell is often a sign of zinc deficiency.

As well as Iron and Zinc, Vitamin B12, Folate, Vitamin D, and Magnesium are also commonly depleted postpartum. It is important to work with a nutritionist, naturopath, or functional medicine practitioner to get a comprehensive assessment of your nutrient status and a plan to replenish with nourishing food and appropriate supplements. At the very least a multivitamin and mineral supplement with activated B vitamins will help to cover all bases.

Postpartum thyroiditis

Pregnancy is a demanding time for the thyroid gland as it has to produce 50% more thyroid hormone to support the baby’s thyroid and brain development.

Postpartum thyroiditis is fairly common after pregnancy and often involves a fluctuation between hyperthyroidism, an overactive thyroid usually in the first three months postpartum, and hypothyroidism, an underactive thyroid usually 6 – 12 months postpartum.

Postpartum thyroiditis is caused by an inflammation of the thyroid gland which is often brought on by the physical changes of pregnancy and childbirth where the human chorionic gonadotropin (HCG) hormone stimulates the enlargement of the thyroid gland.

According to Dr. Sandra Cabot in her book Your Thyroid Problems Solved (2006, p 67), there are two phases to postpartum thyroiditis. ‘In the first phase, while the thyroid gland is inflamed it releases too much hormone into the bloodstream. This phase usually lasts two to four months and it causes the metabolism to speed up’. Hyperthyroid symptoms are usually mild and often go unnoticed but typically would be symptoms such as weight loss, a rapid heart rate, anxiety, sleep issues, increased sweating, and sensitivity to heat. It is easy to see how these symptoms may go unnoticed as many mothers experience anxiety and sleep disturbances in the first few months postpartum.

In the second phase, the thyroid gland does not produce enough hormone and this causes a swing to symptoms of hypothyroidism which can last up to a year and sometimes longer. Typical symptoms can include goitre, which is a swelling of the thyroid gland, fatigue, depression, weight gain, hair loss, sensitivity to the cold, constipation, dry skin, and brittle nails.

Postpartum thyroiditis is considered an autoimmune disease as the majority of women who develop the condition have elevated thyroid antibodies detected in their blood. According to Sandra Cabot, `The body’s immune system incorrectly identifies the thyroid gland as a foreign invader and produces antibodies to destroy it. While women are pregnant, their immune system becomes somewhat suppressed so that they don’t produce antibodies that would harm the developing foetus. After delivery, the immune system becomes reactivated again and it is during this time that the thyroid gland can become inflamed’ (3)

It appears that females who already have an autoimmune condition or have a family history of autoimmunity such as Coeliac Disease, Type 1 Diabetes, Hashimoto’s Thyroiditis, and Psoriasis are much more likely to develop postpartum thyroiditis than those that don’t.

Postpartum thyroiditis affected me in the 1 -2 years after giving birth to my son although at the time my knowledge of the thyroid was limited so I wasn’t aware there was a problem. I had autoimmune Coeliac Disease so I was a likely candidate to develop a further autoimmune condition after the huge amounts of stress my body physically went through with pregnancy and labour. In the first 3 months postpartum I had increased symptoms of anxiety about my child and everything I did and went through a phase of not being able to sleep as I was over vigilant about everything. My son woke a few times at night but I found in those early months I would often struggle to fall asleep again and I would lie awake for hours stressing about the fact that I couldn’t sleep during the limited window I did have to sleep.

As the months went on my symptoms did change to more hypothyroid symptoms such as fatigue, hair loss, dry skin, low body temperature, and an inability to lose weight, this was despite going to the gym and eating healthy. My thyroid symptoms did continue for over a year though so I was one of the unlucky ones that didn’t have their thyroid symptoms resolve at 12 months. When I started trying to conceive when my son was just over a year I started to track basal body temperature and was concerned that my temperature tracked around 35.5 - 8 C each day when the average temperature for a healthy person is around 36.4 – 37.0 C.


If you are concerned that you may have postpartum thyroiditis then a Full Comprehensive Thyroid Panel is recommended to get a true picture of what is happening with your thyroid, although you may not be able to access this test via your doctor.

Whilst researching the thyroid, I came across this very important quote:

“Thyroid dysfunction can affect fertility in various ways resulting in anovulatory cycles, luteal phase defect, high prolactin levels, and reproductive hormone imbalances.

Therefore, normal thyroid function is necessary for fertility and to sustain a healthy pregnancy, even in the earliest days after conception. Thyroid evaluation should be done in any woman who wants to get pregnant with a family history of thyroid problems or irregular menstrual cycles or had more than two miscarriages or is unable to conceive after 1 year of unprotective intercourse. The comprehensive thyroid evaluation should include T3, T4, thyroid stimulation hormone (TSH), and thyroid autoimmune testing such as thyroid peroxidase (TP0) antibodies, thyroglobulin/antithyroglobulin antibodies and thyroid stimulating immunoglobulin (TSI)” (4)

In 2012 this study confirmed a need for a FULL investigation of the thyroid for anyone experiencing recurring miscarriage or infertility issues. Yet here we are 10 years later and still, the majority of women experiencing infertility and recurring miscarriage worldwide are not offered a full thyroid panel from their doctor, just TSH, and Free T4 if TSH comes back as elevated.

During my 10 year journey with secondary infertility, I often had a gut feeling that I was having issues with my thyroid, although it was hard to prove as the limited tests that my doctor and fertility specialist were prepared to do at the time always came back within normal range. This is a worldwide problem that affects many women as conventional thyroid testing is unable to give a full picture of what is going on with the thyroid. As a result, many women live their lives with undetected thyroid issues, wondering why they often don’t feel great.

As well as testing the active hormone T3 and reverse T3, the full thyroid panel test also includes the main thyroid antibodies, which is important to test to see if an autoimmune issue such as Hashimoto’s Thyroiditis or Graves’ Disease is affecting the function of the thyroid gland. This is a particularly important test to do if there is a family history of autoimmune conditions.

Fortunately, these days you can request a full thyroid panel through functional medicine practitioners, naturopaths, and nutritionists like myself who are experienced with functional testing. So, if you feel that you have an issue with your thyroid and are not making much progress with your doctor, then get in touch and I will help you investigate whether your thyroid needs some support.

Additional support

The treatment considerations mentioned in my previous blogs on thyroid support and adrenal support and estrogen dominance can also be used to support hormones postpartum. It is important to support the Hypothalamic Pituitary Adrenal (HPA) Axis as part of a postpartum thyroid treatment plan as it is often the stress of motherhood and the demands of breastfeeding and sleepless nights that starts to take its toll on the adrenal glands which then downregulates the thyroid gland.

With postpartum thyroiditis, it is also important to look at reducing potential immune triggers and supporting the immune system as it is considered to be an autoimmune condition driven by elevated thyroid antibodies. Supporting the overactive immune system with vitamin D, selenium, probiotics, Reishi mushroom, and a gluten free diet can be helpful to reduce thyroid antibodies over time.

The importance of a 3-month preconception care plan

If you are considering trying for baby number two, it is important to spend at least 3 – 4 months getting yourself back up to an optimal position for conception. 3 months is the minimum amount of time you want to be working on preconception care (the same for males as well) focusing on areas such as nutritional deficiencies, diet, gut health, thyroid, and adrenal health. It can take several years to recover from postnatal depletion, so if a second baby is on the cards you want to get started as soon as you can.


(1) Buening B, Hendrickson S, Smith C (2017) Relationship between Pregnancy and Development of Autoimmune Diseases. J Women's Health, Issues Care Vol 6 Issue 1. 21.1.2017

(2) Serrallach O, The Postnatal Depletion Cure, A Complete Guide to Rebuilding Your Health and reclaiming your Energy for mothers of Newborns, Toddlers, and Young Children. Hachette Australia, 2018

(3) Cabot S, Your Thyroid Problems Solved, Holistic Solutions to Improve your Thyroid, WHAS Pty Ltd, 2006 (p 67)

(4) Verma I, Sood R, Juneja S, Kaur S. Prevalence of Hypothyroidism in infertile women and evaluation of response of treatment for hypothyroidism on infertility. International Journal of Applied and Basic Medical Research 2012: 2(1):17-19

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