Pregnancy Hormones: Your Complete Guide to 8 Incredible Ones

Pregnancy hormones are often talked of, being blamed for the various crying spells and nausea that women face in pregnancy. Pregnancy hormones go so much deeper than this, however, and play a huge role in every aspect of pregnancy from conception to birth.

Today we are going to go through 8 pregnancy hormones, and what their role is for both mother and baby. While there are dozens which play out in pregnancy, I wanted to focus on these 8 to get the basics down.

Table of Contents

Pregnancy Hormone #1: Estrogen

Prior to conception, estrogen is produced in the ovaries. Its job is to grow the uterine lining in preparation for a fertilized egg to be received, and triggers the launch of LH, the hormone responsible for triggering ovulation. You can read more about the conception process here.

After conception, estrogen is produced by the placenta, and continues to play a large role in the reproductive process. Estrogen triggers the development of a baby’s organs, and it also promotes the growth of breast tissue.

Estrogen also causes nipples to be darker in order to initiate breastfeeding.

Pregnancy Hormone #2: Progesterone

Progesterone is such a cool hormone that can only be made as a result of LH launching and ovulation. In fact, an empty follicle that has recently ovulated transforms into the corpus luteum, which is an estrogen pumping machine.

Progesterone is such a cool hormone because it makes the conditions for life in the uterus possible. After estrogen is done growing the uterine lining, progesterone swoops in and maintains it, keeping it from growing any more or from shedding in menstruation.

Progesterone levels rise exponentially in the first trimester of pregnancy, and then level out in the second and third trimester.

It also provides nutrients to nourish a fertilized egg once it is implanted.

Once the placenta is developed, it takes over the main production of progesterone in the body at about 10 weeks of pregnancy.

Not only does progesterone play a key role in the early days of pregnancy, but throughout pregnancy it creates an ideal environment for the baby to grow. It does so by keeping the uterine muscle relaxed, preventing contractions, and helps the immune system to tolerate the foreign DNA of a baby.

Pregnancy Hormone #3: Human Chorionic Gonadotropin

Most commonly known as HCG, this is the hormone that women are testing for when they take a pregnancy test. It is produced by the cells surrounding the growing embryo that ultimately form the placenta. Its main job is to maintain the function of the corpus luteum, so that it does not dissipate before the placenta is produced.

This ensures that enough progesterone is maintained by the corpus luteum until the placenta can take over. It rises rapidly during the first trimester, playing a large role in the morning sickness that a mother may experience. In fact HCG levels double every 2 to 3 days during this period of development, and then reaches its peak between 6 and 8 weeks of pregnancy.

Pregnancy Hormone #4: Relaxin

Relaxin is produced by the ovaries and the placenta, and levels are at their highest in the first trimester.

Prior to implantation, but after ovulation, relaxin works alongside progesterone to prepare the uterus for pregnancy. Relaxin also plays a very important role in pregnancy by preventing uterine contractions prior to labor. This prevents premature labor from occurring.

It also works to relax a mother’s blood vessels due to the increased blood volume that comes with pregnancy.

Leading up to labor, it works to relax muscles, ligaments, and joints in a woman’s pelvis in preparation for labor. It also prepares the cervix for labor through softening and widening.

Pregnancy Hormone #5: Oxytocin

Oxytocin is another one of my favorite pregnancy hormones to touch on. Oxytocin is produced by the hypothalamus, and it plays so many roles both in and outside of pregnancy.

One of the main things oxytocin is know for is stimulating uterine contractions for labor. It also increases prostaglandin production, which makes uterine contractions stronger and more progressive.

Oxytocin also stimulates contractions for the birth of the placenta following the birth of the baby.

It also plays a large role in breastfeeding, promoting the movement of milk through the milk ducts.

Though it stimulates contractions, oxytocin is also known as the “love hormone.” It plays a big role in bonding between mother and the infant.

Want to learn more about this cool hormone? Check out this post by Baby Chick.

Pregnancy Hormone #6: Prolactin

Prolactin is produced by the pituitary gland. Its main job has to do with creating the incredible food source of breast milk once the baby is born. Prolactin leads the way by enlarging breasts and producing milk. It is also the hormone that suppresses ovulation in exclusively breastfeeding mothers.

It also works with HCG to maintain the corpus luteum so that progesterone can maintain a pregnancy before the placenta is developed.

Pregnancy Hormone #7: Adrenaline and Noradrenaline

Also known as “fight or flight” hormones, these pick up towards the end of labor to create powerful surges which ultimately help a mother to push her baby out. Adrenaline takes a mother out of labor land and brings greater awareness to her present scenario, which is often when a woman feels like she can no longer do it in labor. Thankfully these thoughts mean a mother is close to the end of her labor.

Adrenaline also protects a baby during the time that they are moving through the pelvis, as oxygen levels naturally drop. It prepares the baby’s lungs to breath in the outside air.

Pregnancy Hormone #8: Beta-Endorphins

Endorphins are an absolutely incredible gift in pregnancy. They are natural pain relief for labor. Endorphins act similarly to drugs like morphine inside of the brain to reduce pain when a physiological birth is taking place. They can also induce elation in the mother.

They also suppress the immune system so that it does not attack the baby as a foreign substance during labor.

They also work to promote the release of prolactin in order to prepare the mother for breastfeeding directly following labor.

SUMMARY

Wow, aren’t all of these pregnancy hormones simply incredible!?! Who knew that there was so much intentional design behind all of them. Let’s summarize each of their roles again:

ESTROGEN

1) Plays a big role in ovulation/conception

2) grows the uterine lining in the follicular phase

3) Triggers development of baby’s organs

4) Promotes growth of breast tissue and promotes milk flow

PROGESTERONE

1) Maintains uterine lining and provides nutrients to implanted egg

2) relaxes uterus and helps body tolerate foreign dna

4) Nourishes baby in the womb

3) Helps relax ligaments and joints in preparation for labor

HCG

Maintains progesterone production until the placenta takes over around 10 weeks
leads to formation of placenta
hcg is what pregnancy tests are detecting

RELAXIN

1) relaxes pelvis, muscles, ligaments, etc in preparation for labor

2) Softens and lengthens the cervix

3) Prevents contractions

4) relaxes blood vessels in preparation for increased blood volume

OXYTOCIN

1) Stimulates uterine contractions in labor

2) stimulates contractions of breast tissue for lactation

3) plays a huge role in parent-infant bonding

PROLACTIN

1) Stimulates uterine contractions on labor