There is a hormone that stands between a fertilised egg and a successful pregnancy.
Without adequate levels of it in the days after ovulation and the weeks of early pregnancy, the uterine lining cannot sustain implantation. The embryo cannot be nourished. The pregnancy cannot continue.
That hormone is progesterone.
And progesterone deficiency insufficient production in the second half of the cycle and in early pregnancy is one of the most common, most undertreated, and most misunderstood contributors to early miscarriage.
This post covers everything you need to know about progesterone, the luteal phase, and what happens when this critical hormone falls short.
WHAT IS PROGESTERONE AND WHAT DOES IT DO?
Progesterone is a steroid hormone produced primarily by the corpus luteum the temporary endocrine structure that forms from the follicle after ovulation.
After the egg is released, the collapsed follicle transforms into the corpus luteum and begins producing progesterone in increasing quantities. This progesterone surge is what drives the second half of the menstrual cycle the luteal phase and it is what prepares the uterine lining for potential implantation.
Progesterone's roles in early pregnancy are extensive and indispensable:
It transforms the endometrium. Under the influence of progesterone, the uterine lining undergoes a dramatic transformation becoming thicker, more vascular, and rich in glycogen-containing glands that will nourish the early embryo. This transformation is called the secretory phase and it is the biological foundation of implantation.
It maintains the uterine lining. Progesterone prevents the shedding of the endometrium the mechanism that causes menstruation. Without adequate progesterone, the lining begins to break down even if an embryo has implanted.
