Pregnancy Hormones

An in-depth look at the hormones that manage your pregnancy from start to finish


 

It’s actually pretty magical. You start with a fertilized egg, and nine months later you have a baby. But the “magicians” in this process aren’t Hogwarts wizards, they are the hormones that manage your pregnancy from start to finish

 

HCG

One of the first things the newly-fertilized egg does is signal your body to start producing HCG (human chorionic gonadotrophin). This hormone is a busy one. It prevents your period from starting (and is the hormone tested for in pregnancy tests). It also causes the queasiness of morning sickness, increases blood flow to your uterus, suppresses your immune system (to prevent it from rejecting the baby) and stops your ovaries from producing more eggs. HCG maintains your pregnancy until the placenta is ready to take over balancing estrogen and progesterone.

Estrogen

Yes, you always have some estrogen in your system. During pregnancy, though, this hormone increases significantly and promotes the growth of ducts and milk-producing cells in your breast (making them tender). Estrogen maintains the lining of the uterus (where the baby is initially attached) and helps the uterus grow.  It’s also a prime mover in the growth and development of the baby.

Progesterone

Progesterone levels normally go up in the second half of your menstrual cycle, then drop just before your period starts. When you are pregnant, though, the progesterone levels remain higher. Progesterone is responsible for much of the tiredness and moodiness of pregnancy, and for the softening of the cartilage in your pelvis that makes it easier for your baby to be born. (To accomplish this, it works with another hormone, relaxin.)

After your baby is born, it’s the drop in progesterone once the placenta is delivered that allows the hormone prolactin to cause milk production to increase.

HPL

Your body puts a lot of effort into preparing to breastfeed. The hormone HPL (Human Placental Lactogen) causes your breasts to start making colostrum during the weeks before your baby is born. It also changes your metabolism, so that more glucose is available for your growing baby. 

Oxytocin

This is another hormone that is always present in your system (it spikes during orgasm, for example) but your uterus is relatively insensitive to it until it’s time for labour to begin. Then oxytocin stimulates the contractions that open the cervix and allow the baby to emerge. After the birth, the baby’s suckling at your breast releases more oxytocin and helps your uterus to contract, reducing post-partum bleeding. 

Prolactin

This hormone starts its work once the placenta is delivered, and signals your breasts to get busy making milk. You produce more prolactin during night feedings than during the day, so midnight feeds can be important to keep up your milk supply.

That’s not all. There are actually many other hormones playing more minor roles in this amazing process. In the end, though, you won’t be thinking much about HCG and HPL; you’ll just be focused on the baby you finally get to hold.


 

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