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The Hormone guide

Hormones play a critical role in our body and ensure that vital functions are functioning properly. They regulate, among other things, our metabolism, fluid balance, heart rhythm and our growth, and they also play a major role in influencing our mood.

How do my hormones affect me?

Before and during pregnancy, your hormones affect your fertility, sexual function and growth, as well as your development. The hormones are also the ones responsible for that "glow" that everyone always talks about - when your hair and nails grow and feel so good during pregnancy - but your hormones can also cause sudden crying jags and changes in your mood. This is because all your hormones now work at the same time, and it creates differences in hormone levels that your body is not used to.

The fact that your mood can go up and down, however, does not have to be seen as something negative, but it is believed that this openness to emotions plays a role in becoming a parent and embracing your child. The hormones also ensure that the baby grows and develops during pregnancy while at the same time preparing your body to give birth. In order not to feel abandoned, tired or irritated by all these hormones and their effect on your body during your pregnancy, we have listed the most important hormones to explain to you how they affect both your pregnancy and childbirth.

Human chorionic gonadotropin (HCG)

HCG is a hormone that is secreted early in the pregnancy. It stimulates the corpus luteum, which in turn produces progesterone. The corpus luteum is what provides the baby with nutrition before the placenta is in place and the progesterone that is formed in the corpus luteum ensures that the pregnancy continues. HCG is also the hormone that is measured in the urine when you take a pregnancy test, i.e when you urinate on the stick.

Estrogen

Estrogen is a hormone that is produced early in the pregnancy. Together with progesterone, it causes the uterine lining to grow and thicken so that the egg can attach and the pregnancy grows. Estrogen also helps in fetal development and the development of the placental function. It also affects your breasts, so if you experience that they grow and sore, it is because the estrogen prepares them for breastfeeding already during the first trimester. The estrogen also makes you more sensitive to smell, taste and touch, which can be wonderful but sometimes cause nausea. The high estrogen levels during a pregnancy also mean that you lose less hair than usual and that your nails grow faster. Later during the pregnancy, estrogen also helps prepare your body for birth. Estrogen together with prostaglandin, progesterone and oxytocin is responsible for the start of labor. Prostaglandin is the hormone that softens the uterine tube and progesterone is the hormone that enables the prostaglandin to work.

Progesterone

Progesterone is sometimes called the pregnancy-preserving hormone as it allows the uterine lining to receive the egg and cause it to attach. Progesterone is produced in the beginning of the pregnancy and together with estrogen ensures that your baby receives nutrition and circulation. The baby is nourished by increasing circulation and blood flow to the uterus, which is something that is required in early in the pregnancy.

Progesterone also makes the smooth muscle - the muscle found in, for example, the urinary tract, blood vessels, trachea and gastrointestinal tract - more resilient. When smooth muscles become more compliant, the risk increases that you experience, for example, heartburn and acid regurgitation. This is because the stomach is not as tense as before, and therefore stomach acid can leak. It also makes your intestines work more slowly and can therefore cause nausea and constipation. Veins and blood vessels are also affected and this is the explanation for why you are more likely to suffer from varicose veins during a pregnancy.

Progesterone causes the blood supply to be redirected in the body so that your brain receives less blood than before. At the same time, this also reduces the consumption of, for example, glucose. This, together with the fact that the brain receives less blood, makes the brain function slower - so blame your forgetfulness and temporary confusion on the progesterone! High levels of progesterone have long been linked to sudden changes in mood. Mild irritation and anger are thus due to hormones and to a very high degree caused by progesterone.

Oxytocin

Oxytocin is one of our most important hormones during pregnancy and childbirth. Oxytocin is the only hormone that does not cause any discomfort but is often called our "feel-good hormone". It is secreted when we feel good, eat well, spend time with people we like, through physical proximity and during pregnancy and birth. Oxytocin also relieves pain during childbirth while ensuring that the uterus contracts and the cervix opens. Oxytocin also plays a major role in milk production and its association with the newborn baby.

You can read more about the different roles of oxytocin under the category Oxytocin in Articles & Tools → Pregnancy.

Prolactin

The main task of prolactin is to produce breast milk and to stimulate breast growth together with estrogen. But prolactin is not only milk-producing but also acts in many other areas, such as our immune system, our mental health and metabolism. It is also the hormone that makes us humans - and mammals for that matter - brood and feel the instinct to protect our children. Like oxytocin, prolactin helps with creating attachment to the newborn and is excreted during breastfeeding. During breastfeeding the levels of prolactin are high, a surge in prolactin also prevent ovulation and can in cases act as a contraceptive.

Read more about this in our article "Can I get pregnant while breastfeeding?" which is about the Lactation amenorrhea method. You can find it under the category “Quarter 4” in Articles & Tools.

Relaxin

Relaxin begins to be produced in week 14 of the pregnancy and it makes your joints and ligaments softer. This is done to prepare the body for the growing pregnancy and also for birth, but it can mean that you experience pain from the pelvis and lumbar spine as the joints in the pelvis become more mobile.

Prostaglandins

Prostaglandins are formed throughout the entire pregnancy, but their effect is held back by progesterone. When progesterone levels eventually drop in the later parts of the pregnancy, prostaglandins can begin to work. They then soften the uterine tube to make it ready to mature and open during labor. Prostaglandins are also used as medicines in various forms when starting a labor.

Sources: - Kaplan, A. (red.) (2009). Lärobok för barnmorskor. (3., omarb. uppl.) Lund: Studentlitteratur. - Myles, M.F., Marshall, J.E. & Raynor, M.D. (red.) (2014). Myles textbook for midwives. (16th edition). Edinburgh: Elsevier.