How Does Progesterone Affect Moms and Newborn Babies?

New Research Conducted By The National Institutes Of Health Found That Unbalanced Progesterone Signals May Have A Causal Relationship With Preterm Labor Or Prolonged Labor.

When it comes to the duration of a woman’s pregnancy, being born after the appropriate number of weeks can be essential for the healthy development of a baby. Because gestation time is so critical, medical professionals are always trying to understand more about the biological processes that can impact when babies are born.

According to new research conducted by the National Institutes of Health and published online in the Proceedings of the National Academy of Sciences, unbalanced progesterone signals may cause some pregnant women to experience preterm labor or prolonged labor. Importantly, this study provides novel insights for developing treatments.

Here’s everything you need to know about how progesterone can affect pregnancy. 

a mother holding a baby
Many hormones play a part in maintaining a woman’s pregnancy, and progesterone is especially involved in gestational processes. 

The Role of Progesterone in Pregnancy

Progesterone — sometimes referred to as “the pregnancy hormone” — is a female hormone found naturally in a woman’s body. Playing an important role before and during a pregnancy, progesterone helps with preventing the uterus from contracting and prematurely going into labor. 

Progesterone Throughout Pregnancy

After an egg is fertilized, progesterone stimulates the growth of blood vessels. In turn, these vessels supply the endometrium (the lining of the womb) with blood and stimulate the endometrium’s glands to secrete nutrients that nourish the new embryo. 

Additionally, progesterone prepares the uterus’ tissue lining to allow the fertilized egg to implant while also maintaining the endometrium during the pregnancy. 

During pregnancy, progesterone also plays a role in the:

  • Development of the fetus
  • Growth of maternal breast tissue
  • Regulation of lactation
  • Strength of the pelvic wall muscles in preparation for labor 

Ultimately, the level of progesterone in a woman’s body consistently rises over the course of a  pregnancy until the baby is finally born.

Progesterone and the Regulation of Contractions

Progesterone’s regulation of uterine contractions occurs through molecular signaling that involves progesterone receptor types A and B — also referred to as PGR-A and PGR-B. 

Prior to the study from the National Institutes of Health, previous research has shown that PGR-A is responsible for regulating processes connected to the initiation of childbirth, and PGR-B affects molecular pathways connected to maintaining the normal course of pregnancy. 

Moreover, the National Institutes of Health study has built on these findings by revealing that the abundance of PGR-A and PGR-B could be essential to promoting a healthy pregnancy. 

a doctor looking at an ultrasound
If you’re an expecting mother, it’s important to be aware of possible risk factors that could lead to birth complications.

Preterm Births and Prolonged Labor

In any pregnancy, a preterm birth or prolonged labor can have serious impacts on both mothers and babies. Because progesterone can impact both of these birth-related events, it’s important to understand their definitions and effects.

Preterm Births

A baby developing over the course of a pregnancy goes through important stages of growth. Specifically, many important developmental milestones occur in the final months and weeks before a baby is born. 

When a baby is born too early — before 37 weeks of pregnancy have been completed — it is known as a premature or preterm birth. Preterm births affect 10% of all pregnancies and are the primary cause of worldwide neonatal morbidity and mortality. Basically, the risk of death or serious disability for an infant increases the earlier that the infant is born. Babies who survive a preterm birth can experience:

  • Breathing issues
  • Intestinal (digestive) problems
  • Bleeding in the brain
  • Developmental delays (long-term effect)
  • Lower performance in school (long-term effect)

Although medical experts don’t know all the reasons that some babies are born too early, there are some known risk factors that increase the chance that a woman will have a preterm birth. Some risk factors include:

  • Being pregnant with multiple babies
  • Tobacco use and substance abuse
  • Short time between pregnancies (less than 18 months) 

Still, a woman can still have a premature birth even if she has no known risk factors. 

Prolonged Labor

If a woman experiences prolonged labor, that increases the risks of:

  • Infection
  • Uterine rupture
  • Neonatal distress

Notably, prolonged labor can harm both the mother and the infant and can lead to cesarean delivery.

a father cradling a newborn baby
The National Institutes of Health Study found that progesterone signaling affects the duration of a woman’s pregnancy. 

The Study: How Progesterone Affects Pregnancy Duration

In the National Institute of Health study, scientists examined the ways that unbalanced PGR-A and PGR-B signaling can impact pregnancy duration. 

"We used genetically engineered mouse models to alter the ratio of PGR-A and PGR-B in the muscle compartment of the uterus, called the myometrium," said senior author Francesco DeMayo. "Our team found that PGR-A promotes muscle contraction and PGR-B prevents such contraction, and we identified the biological pathways influenced by both forms."

According to Steven Wu, Ph.D., first author on the study and staff scientist at DeMayo’s lab, progesterone treatment that is aimed at preventing premature labor can help a subset of patients. Particularly, the research team found new molecules that control uterine muscle contraction, and these molecules could serve as therapeutic targets in the future. 

Wu also noted that the current study could help advance treatment for labor dystocia — the clinical name for abnormally slow labor.

"Hormone signaling in pregnancy is complicated and involves both the hormone levels and the types of receptors in the uterus that sense the hormones," said co-first author Mary Peavey, M.D. "This publication sheds light on how hormones influence labor and can thus be used to help women when the uterus goes into labor too soon or for a prolonged period."

a mother hugging a baby
If you are pregnant and have concerns about your hormone levels or the health of your baby, be sure to talk to your doctor. 

During pregnancy, it is important to be aware of the specific roles that certain hormones play in infant development and labor. As a result of a new study from the National Institutes of Health, researchers and medical professionals now have a clearer understanding of the ways that unbalanced progesterone signals might cause pregnant women to experience preterm or prolonged labor. 

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