Pregnancy Hormones 101

In Pregnancy/Postpartum by pelv_admin4 Comments

Pregnancy is wild. Someone is walking around growing a human being. It blows my mind every time I see a pregnant person and here at The Pelvic Health & Rehabilitation Center, we get to see a lot of pregnant people! 

Now a lot of things happen during pregnancy, and hormones are a big key player in the process. You may recall a blog post I did previously talking about hormones in general. In this post I want to dive in a little deeper and talk about hormones during pregnancy. 

There are several hormones, but let’s focus on the major ones: 

  • Estrogen
  • Progesterone
  • Oxytocin
  • Prolactin
  • Relaxin

Estrogen is probably the most well known hormone. It’s like a Kardashian: big name recognition, but what does it actually do ? During pregnancy, estrogen production increases and it will get up to 30 times its normal levels! The main role estrogen plays is it helps stimulate uterine growth. It will increase blood flow to the vagina and other areas of the body. If you are getting nose bleeds or feeling congested while you are pregnant, estrogen is possibly to blame! 

However, don’t go blaming estrogen for everything. Progesterone is hard at work during pregnancy. In fact, the main job of the ovaries during the first seven weeks of pregnancy is to produce progesterone. This hormone is helping to maintain the endometrial layer that the growing embryo is attached to and it helps maintain the pregnancy. Therefore, low levels of progesterone during a pregnancy increases the risk of a miscarriage. Progesterone is steadily increasing during pregnancy and is one of the main causes of morning sickness. 

Progesterone also stimulates the breast lobes to prepare for milk production and helps the body store more fat as the pregnancy progresses. Progesterone is helping to relax things in the uterus, but other areas of the body can be impacted. For example, the lower part of the esophagus can have decreased tone due to progesterone and this can result in increased heartburn during pregnancy. 

Progesterone isn’t the only hormone helping to relax things during pregnancy. While its name is deceiving, the hormone relaxin has several jobs. It is going to inhibit uterine activity and it will help soften the cervix. Although, it is a myth that it is 100% responsible for relaxing all of the ligaments during pregnancy, it will help relax the joints, such as the pubic symphysis to help get ready for delivery. 

Speaking of delivery, let’s talk about oxytocin which increases at the end of pregnancy and during labor. This hormone is being suppressed by progesterone during pregnancy because oxytocin is going to help stimulate uterine contractions. It will continue to work after the baby is born to help the uterus contract to expel the placenta. This hormone may be used to induce labor or help it progress but is commonly referred to by its brand name: pitocin. Oxytocin also helps stimulate the milk-ejection reflex that is necessary for breastfeeding. 

Breastfeeding happens thanks to a feedback loop created by oxytocin which promotes milk let down and then another hormone, prolactin, which is responsible for milk production. Prolactin will lead to enlargement of the mammary glands and as a result each breast can increase by one pound each! As a result, new moms may notice more back or neck pain. So, it may be a good idea to invest in some good quality bras to make sure your breasts are getting the support they need and deserve! 

The physical therapists at PHRC are experts in helping women prepare for pregnancy, labor and delivery, and recover in the postpartum period. If you want to optimize your musculoskeletal health before, during, or after pregnancy please give us a call! 


Additional Resources:

Why All PostPartum Women Need Pelvic Floor Physical Therapy

The 4th Trimester: Postpartum Pelvic Pain is Common but Not Normal part 1

The 4th Trimester: Postpartum pelvic Pain is Common but Not Normal Part 2




  1. All I can say that Pelvic Health Services have a lot of benefits for your health. Thanks for the information I have learned a lot!
    Thank you very much!

  2. Thanks! This article was really awesome, particularly since I was searching for thoughts on this topic last Sunday.

    1. Hi Jane,
      We are so happy to hear that this article helped! We hope you stick around as we continue to publish more informational articles.

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