Dr Haleema Sheikh, a specialist in integrative women’s health and bioidentical hormone balancing for the Marion Gluck Clinic, discusses progesterone in early pregnancy
Progesterone is one of women’s vital reproductive hormone and plays a key role throughout pregnancy. It is often overshadowed by more widely discussed hormones such as beta hCG and oestrogen. For midwives working in early pregnancy care, fertility support, or the recurrent miscarriage pathways, understanding progesterone’s functions and how it can be supported can have a potentially profound impact on clinical practice and women’s experiences.
In this article we will explore the origins of the name progesterone, its essential physiological role on our organs and tissue, contributing factors to suboptimal levels, and evidence-informed approaches including lifestyle, nutrition, supplements, and body identical/bioidentical progesterone support.
The word progesterone is derived from ‘pro gestation’ literally meaning in favour of pregnancy and points to the hormones central purpose in preparing the body for pregnancy and sustaining it in its early stages. Progesterone is produced in the second half of the cycle after ovulation when a mature follicle in the ovary releases an egg. The remnant of the follicle, the corpus luteum is responsible for the rise in progesterone which plays a foundational role in creating the conditions in the womb for a successful implantation and a healthy first trimester. After this the placenta takes over the production of ongoing progesterone for the rest of the pregnancy.
Progesterone is a steroid and a nuclear hormone which means its impact on cells is multifaceted, and it can act as a classical nuclear hormone to regulate long-term gene expression while also using rapid non-genomic pathways to quickly influence cellular activities, particularly in the nervous and immune systems.
It has multiple physiological roles in early pregnancy
- Preparing the endometrium- in the second half of the cycle progesterone transforms the endometrium from a proliferative lining under the influence of oestrogen to a secretory, nutrient rich environment. This change in the womblining is essential for the implantation of the blastocyst allowing it to anchor and develop. If there is inadequate progesterone the implantation may be shallow or unstable which increases the risk of biochemical pregnancy loss or very early miscarriage
- Supporting Immune modulation- in order to tolerate the growth of ‘foreign’ foetal tissue which contains genetic material from the father the maternal immune system must be modulated to become tolerant and anti inflammatory. Progesterone promotes T-helper 2 immunity which reduces the risk of immune-mediated pregnancy loss. However, this shift in immunity can make women more vulnerable to infection risks which is important to be aware of.
- Reducing uterine contractility- progesterone relaxes smooth muscle including that of the uterus. This prevents early uterine irritability and contractions that might interfere with embryo implantation or placental development. Many women who experience spotting or early cramping during pregnancy have progesterone levels that are borderline or low for their gestational age.
- Supporting Early Placental development- in the first trimester progesterone promotes the growth and function of trophoblast cells (outer layer of the early embryo) that encourage angiogenesis (production of blood vessels) which supports the developing placenta until the placenta can take over progesterone production at around the 9–10-week mark. Thus, insufficient progesterone in this early phase is being acknowledged as a potential contributor for recurrent early pregnancy loss.
- Preparing the breast for lactation. Progesterone also works in synergy with oestrogen and prolactin hormones. It stimulates the physical development of the breast as well as inhibiting the production and release of milk till post-partum.
Given these diverse roles, it is not surprising that poor progesterone production as a result of poor ovulation, luteal phase issues, or individual variations can increase the risk of early pregnancy loss.
Progesterone is very sensitive to stress and when women have excessive pressures for whatever reason such as mental, physical, over exercising, emotional, financial etc it can result in the body not feeling safe to procreate and it lowers progesterone production. This is a protective response by the body to focus on survival and cortisol production.
This knowledge can help us support women trying to get pregnant have healthy ovulation and a ‘strong’ corpus luteum response to produce progesterone. It is also