Luteal phase defect
The short version
Luteal phase deficiency has been proposed for decades as a cause of infertility and recurrent miscarriage. No reliable diagnostic test exists, and it is not established as an independent cause of infertility.
That matters, because tests and treatments for it are still offered.
What the luteal phase is
The stretch between ovulation and your next period, when the corpus luteum produces progesterone to prepare and maintain the uterine lining. Typically 12 to 14 days.
Why it is hard to diagnose
Endometrial biopsy dating — histological dating was the traditional method. It does not reliably distinguish fertile from infertile women and is no longer recommended for this purpose.
Single progesterone measurements — progesterone is released in pulses, so a single value fluctuates widely through the day. A low reading may reflect timing rather than deficiency.
Luteal phase length — a consistently short luteal phase, under about 10 days, is a more useful signal than any blood test, and it is something you can track yourself.
Look for causes that are diagnosable
Conditions that present the same way and are treatable:
- Thyroid dysfunction
- Raised prolactin — note a single raised result should be repeated under calm conditions, and macroprolactin excluded
- PCOS and irregular ovulation
- Functional hypothalamic amenorrhoea — from low body weight, weight loss or heavy exercise
- Approaching menopause
These are worth testing for. "Luteal phase deficiency" as a standalone diagnosis usually is not.
On progesterone supplementation
In IVF, luteal support with progesterone is standard and well established — stimulation and retrieval disrupt normal corpus luteum function. ESHRE (2026) recommends progesterone for luteal phase support.
In natural conception, the picture differs. ASRM (2026) states there is no evidence supporting checking progesterone levels in unassisted pregnancies and supplementing based on the level — a practice that remains common.
For recurrent pregnancy loss, vaginal progesterone may be considered in early pregnancy where there is vaginal bleeding and/or recurrent unexplained miscarriage, using shared decision-making.
On dydrogesterone specifically: ESHRE (2026) records published reports of an association with congenital malformations, causality not established. Relevant given how widely it is prescribed in India.
If it has been suggested to you
Reasonable questions: what was measured, when in the cycle, and what would change based on the result?
If progesterone supplementation is proposed for natural conception on the basis of a single blood level, ask what evidence supports it.
Frequently Asked Questions
What are the signs of a luteal phase defect?▾
Signs include: a cycle consistently shorter than 26 days (short luteal phase under 11 days); spotting between ovulation and the period (especially 5–8 days after ovulation); low Day 21 progesterone (<3–10 ng/mL); recurrent early miscarriage or difficulty sustaining a very early pregnancy. BBT charting can reveal a short post-ovulation temperature rise.
Does low progesterone prevent pregnancy?▾
Severe progesterone deficiency can impair implantation and early pregnancy maintenance. However, the clinical significance of mild LPD in natural cycles is debated. Progesterone supplementation is standard in all IVF and IUI cycles. For natural cycles, treating any underlying cause (thyroid disease, hyperprolactinaemia) and using vaginal progesterone from post-ovulation is reasonable, particularly in women with prior miscarriage.
Can you get pregnant with luteal phase defect?▾
Yes — LPD is one of the more treatable fertility conditions. Progesterone supplementation in stimulated IUI and IVF cycles effectively corrects this in most cases. For natural cycles, treating the underlying cause (particularly thyroid disease) often restores normal luteal function. The live birth rate with appropriate supplementation in IVF cycles is not significantly different from patients without LPD.