Luteal Phase and Miscarriage

In testing for infertility causes or as part of recurrent miscarriage testing, your physician might bring up the term luteal phase defect, or a shortened luteal phase. Here's what these statements mean.

The term luteal phase usually refers to the second half of the menstrual cycle — the time from ovulation to the start of the menstrual period. In women with a standard 28-day menstrual cycle and who ovulate on the fourteenth day, the luteal phase is 14 days long.

One characteristic of the menstrual cycle is that lots of things are going on in your body at any given time. In the first half of your menstrual cycle, various hormonal fluctuations take place to prepare an egg for ovulation and ultimately to cause ovulation. During the luteal phase, the major hormonal event is the rise of progesterone levels and the uterine lining's preparation to receive a fertilized egg (in the event that conception has occurred).

Luteal phase defect (also called luteal phase dysfunction or luteal phase deficiency) means that a problem exists with the luteal phase, with the result being that the uterine lining might not be optimally prepared for implantation of a fertilized egg.

Luteal phase defect is a theoretical cause of infertility as well as early miscarriages. In other words, there's no proof that luteal phase defect leads to infertility or miscarriage. The idea underlying luteal phase defect is that if the uterus is not fully prepared to support a pregnancy, then either a woman will not get pregnant at all or the pregnancy will not implant properly and will ultimately miscarry. Luteal phase defect results in a shorter than average luteal phase (a woman getting her period 10 days after ovulating rather than 13 or 14 days afterward).

Some people believe that low progesterone might be at the root of recurrent miscarriages; a woman with a luteal phase defect and low progesterone would theoretically be less able to support a pregnancy. Supplementing progesterone to prevent miscarriage is a controversial treatment, however, because no scientific evidence has ever proven that progesterone supplementation improves pregnancy outcomes.

In decades past, an endometrial biopsy was sometimes performed to take a look at the cellular or histological makeup of the endometrial (uterine) lining and figure out whether its maturity lagged behind what was expected. However, there is so much variability in how the uterine presents cellularly that an endometrial biopsy is no longer considered useful.