Hormones during pregnancy
Hormones are chemical substances produced in the glands of the body that help regulate functions in different organs. Their role is to act as messengers throughout the body, and among them are the pregnancy hormones, which play a key role in the development and maintenance of pregnancy.
Hormones travel through the bloodstream to carry signals from one part of the body to another. In this way, they communicate with target organs so that these can respond to the body’s needs at each moment.
During pregnancy, a woman’s body undergoes a series of hormonal changes that are fundamental for the proper development of the foetus and for preparing the maternal body for birth. These changes are orchestrated by various hormones, each playing specific roles at different stages of pregnancy.
The most important pregnancy hormones
Pregnancy is a time when hormones play a crucial role. They are responsible for preparing the uterus for embryo implantation and ensuring its development during the first weeks.
The main hormones involved in pregnancy are:
Human Chorionic Gonadotropin (hCG)
This hormone is mainly produced in pregnancy by the cells that will eventually form the placenta. Its function is to maintain progesterone levels through the corpus luteum and prevent menstruation. As it can be found in blood and urine, this is the hormone used to diagnose pregnancy.
Urine pregnancy tests detect the presence of this hormone.
Oestrogen
Oestrogens are hormones secreted by the follicles as they grow. They are responsible for preparing the endometrium and stimulating its growth to enable embryo implantation.
Progesterone
Progesterone is produced by the corpus luteum in the ovary and is responsible for maintaining pregnancy during the first weeks. It is crucial for sustaining the endometrium and preventing uterine contractions, ensuring a suitable environment for embryo development.
It also helps regulate the immune system, preventing the mother’s body from rejecting the foetus.
FSH and LH
These hormones are responsible for the growth and development of follicles in the ovary. Proper regulation is essential for adequate follicle growth and for the oocyte to mature.
Main pregnancy hormones and their functions
| Hormone | Stage | Function |
|---|---|---|
| Human Chorionic Gonadotropin (hCG) | Early pregnancy | Stimulates progesterone production |
| Progesterone | Early pregnancy | Maintains the uterine lining for pregnancy and prevents ovulation |
| Oestrogen | Throughout pregnancy | Stimulates growth of the uterus and breasts, promotes foetal development, regulates other hormones |
| Prolactin | Throughout pregnancy | Prepares the mammary glands for lactation and stimulates milk production |
| Oxytocin | During labour | Stimulates uterine contractions and facilitates the baby’s delivery |
| hCG (human chorionic gonadotropin) | Early pregnancy | Stabilises the corpus luteum and maintains progesterone production in early pregnancy |
| Cortisol | Throughout pregnancy | Helps regulate maternal and foetal metabolism and prepares the body for labour |
| Relaxin | Early pregnancy and during labour | Relaxes uterine muscles and aids embryo implantation |
Which hormone levels are favourable for pregnancy?
Below is a table with the hormone levels during pregnancy, showing the minimum and maximum values considered favourable for optimal functioning during conception and gestation:
| Hormone | Minimum values | Maximum values |
|---|---|---|
| FSH | 4 mIU/ml | – |
| LH | 2 mIU/ml | 10 mIU/ml |
| TSH | 0.2 mIU/ml | 4.7 mIU/ml* |
| Prolactin | 2 mIU/ml | 25 ng/ml |
| Oestrogen | 27 pg/ml | 161 ng/ml |
| Progesterone | 5 ng/ml | 20 ng/ml |
The importance of hormonal balance
Precise hormonal control is essential for achieving a successful pregnancy. Women who experience conditions that alter hormone levels, such as thyroid problems, may face difficulties conceiving naturally.
Hormonal problems that may hinder pregnancy
The ability to conceive and carry a pregnancy to term is closely linked to hormonal balance in a woman’s body. Hormonal problems can significantly affect fertility and the chances of becoming pregnant. Some of the most common hormonal issues that may hinder conception are:
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Polycystic Ovary Syndrome (PCOS): In this condition, hormone levels such as insulin and luteinising hormone (LH) may be imbalanced, leading to the formation of cysts in the ovaries. These imbalances can interfere with proper ovulation and reduce fertility.
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Hypothyroidism: When the thyroid gland does not produce enough thyroid hormone, hypothyroidism may develop. This imbalance can disrupt ovulation and regular menstrual cycles. It can also affect the production of key pregnancy hormones such as oestrogen and progesterone.
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Hyperprolactinaemia: This disorder is characterised by elevated levels of prolactin in the blood. It can interfere with ovulation and menstrual cycle regularity. High prolactin levels may inhibit the action of hormones that stimulate ovulation, making it harder to conceive.
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Hypogonadism: This involves low levels of sex hormones such as oestrogen and progesterone. It can cause menstrual irregularities, anovulation (lack of ovulation), and difficulties conceiving. Adequate balance of these hormones is essential for uterine preparation and pregnancy maintenance.
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FSH and LH imbalances: Both excess and deficiency of follicle-stimulating hormone (FSH) and luteinising hormone (LH) can affect proper follicle maturation and ovulation. These hormones play a vital role in oocyte release and in preparing the body for conception.
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Adrenal gland disorders: Conditions affecting the adrenal glands, such as Cushing’s syndrome, can cause abnormal levels of hormones like cortisol and DHEA. These imbalances can interfere with ovulation and affect fertility.
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