Background: Miscarriage is defined as spontaneous loss of pregnancy prior to 20 weeks gestation. With an estimated risk of 15% of clinically confirmed pregnancies ending in miscarriage, it is the most common adverse event in pregnancy. Woman's age is the primary risk factor for miscarriage, while medical conditions, including hormonal abnormalities, are also associated. Progesterone is essential for maintaining pregnancy. A short luteal phase may reflect inadequate levels of progesterone production, but it is unclear whether a short luteal phase correlates with an increase in the risk of miscarriage.
Methods: Using a cohort study design, we conducted a secondary data analysis from four cohorts of couples who used a standardized protocol to track biomarkers of the female cycles. A short luteal phase was defined as less than 10 days, with < 11, < 9, and < 8 days as alternate definitions in sensitivity analyses. We included women who experienced a pregnancy with a known outcome, identified the length of the luteal phase in up to 3 cycles prior to conception and assessed the relationship with miscarriage using a modified Poisson regression analysis, adjusting for demographic characteristics, smoking, alcohol use and previous pregnancy history.
Results: In our sample of 252 women; the overall miscarriage rate was 18.7%. The adjusted incident risk ratio of miscarriage in women who had at least one short luteal phase < 10 days, compared to those who had none, was 1.01 (95% CI: 0.57, 1.80) Similar null risk was found when assessing alternative lengths of short luteal phase. Women who had short luteal phases < 10 days in all 3 cycles prior to the conception cycle had an incident risk ratio of 2.14 (95% CI: 0.7, 6.55).
Conclusions: Our study found that a short luteal phase in the three cycles prior to conception was not associated with higher rates of miscarriage in an international cohort of women tracking their cycles, but our sample size was limited. Further research to determine if short luteal phases or luteal phase deficiency is associated with early pregnancy losses among preconception cohorts with daily tracking of cycle parameters, in addition to progesterone and human chorionic gonadotropin levels, is warranted. Additionally, future studies should include women with recurrent short luteal phases as a more likely risk factor than isolated short luteal phases.
Keywords: Early pregnancy loss; Fertility; Maternal age; Miscarriage; Pregnancy; Progesterone; Reproductive life plan; Short luteal phase.
This study looks at whether women have a higher risk of miscarriage if the second half of their menstrual or reproductive cycle is shorter than normal. The second half of the cycle, referred to as the luteal phase, is normally 11 to 16 days long. If the luteal phase is too short this may suggest a woman does not have enough progesterone, the hormone essential for maintaining pregnancy.This study included 252 pregnant women for whom we had data on the length of at least one luteal phase prior to pregnancy and for whom we knew the outcome of the pregnancy. Almost one-fifth of the women in our study had a miscarriage. However, we found there was no difference in the risk for miscarriage if women had a short or a normal luteal phase.
© 2022. The Author(s).