Could an Underactive Thyroid Be the Reason Pregnancy Is Taking Longer?

How Thyroid Problems Affect Female Fertility

The thyroid helps control how the body uses energy and how certain hormones work. If it becomes  underactive or overactive, it can throw off the balance of other hormones, too. That is where fertility  problems can start. 

For women, thyroid issues often show up through changes in the menstrual cycle. Periods may suddenly  become irregular, heavier, lighter, or more spread out than before. Some women stop getting periods  regularly altogether. (Source: Womens Health)  

An underactive thyroid, also known as hypothyroidism, can make ovulation less predictable. In some cases,  the ovaries may not release an egg every month. If ovulation is irregular, it becomes much harder to know  when the fertile window is and more difficult to conceive naturally. 

Some women notice other symptoms at the same time, even if they do not realize they are connected.  Feeling tired all the time, gaining weight more easily, feeling cold, having dry skin, low mood, and  constipation can all be signs of an underactive thyroid. 

An overactive thyroid can also affect fertility. Women may notice shorter cycles, lighter periods, trouble  sleeping, feeling anxious, or feeling like their heart is racing more often than usual. Even when these  symptoms seem unrelated, they can still interfere with hormone balance and make pregnancy harder. 

Why Men Can Be Affected Too

Thyroid problems do not only affect women. Men can be affected too, although it is talked about less often. For men, thyroid hormones help support sperm production and testosterone levels. If thyroid hormone  levels are too high or too low, sperm may not move as well, sperm count can drop, and sex drive may  decrease. Some men also notice erection problems, tiredness, or mood changes. 

Because these changes usually happen slowly, many people blame stress, poor sleep, or getting older. They  do not always realize there could be an underlying thyroid issue. (Source: NCBI)  

Why Thyroid Testing Matters During Fertility Treatment

This is one reason fertility specialists often include thyroid testing early on, especially before IVF. A simple  blood test can show if thyroid hormone levels are outside the normal range. If they are, treatment can often  help. (Source: BTF Thyroid)  

For many people, treating a thyroid problem helps bring the body back into balance. Periods may become  more regular, ovulation may improve, sperm quality may increase, and it may become easier to conceive. Thyroid problems can also affect pregnancy after conception happens. If hormone levels are not well  controlled, there may be a higher risk of miscarriage or other complications. That is why doctors usually want  thyroid levels to be stable before and during pregnancy. 

The thyroid may be small, but it has a surprisingly big influence on fertility. When pregnancy is taking longer  than expected, and there is no clear reason why, the thyroid is one of the first places worth checking. Sources:  

Womens Health - https://womenshealth.gov/a-z-topics/thyroid-disease 

NCBI - https://pmc.ncbi.nlm.nih.gov/articles/PMC3826086/ 

BTF Thyroid - https://www.btf-thyroid.org/thyroid-function-tests