How to lengthen your luteal phase naturally

When you're trying to get pregnant, your luteal phase -- the part of your cycle that happens after ovulation -- needs to be long enough for the embryo to find a spot in the uterus and implant. But how do you make sure it's long enough, and what does "long enough" even mean?

What is the luteal phase?

Your cycle splits into two parts: the follicular phase (cycle day 1 through ovulation) and the luteal phase (the day after ovulation through the end of your cycle). Here's roughly what to expect, timewise:

• Day 1 of the luteal phase: sperm and egg meet. The fertilized egg is now a zygote.
• Days 1-5: the embryo develops and expands daily. By day 5 or 6 it reaches a milestone and becomes a blastocyst.
• Days 8-10: the blastocyst is ready to implant in the uterus -- as soon as that happens, you're officially pregnant.
• Days 10-14: hCG is secreted after implantation, and levels usually take a few days to become high enough for a positive test.

What is luteal phase deficiency / short luteal phase?

What happens if fertilization and early development go fine, but your period arrives just as implantation should be happening? That's a short luteal phase, or luteal phase deficiency. Since most healthy embryos implant within about 10 days of ovulation, a luteal phase shorter than 10 days is often the working definition.

Which hormones are involved?

Progesterone is the key player. After ovulation it's secreted by the corpus luteum (the structure that housed the egg before ovulation). If you're pregnant, hCG signals the corpus luteum to keep producing progesterone. If implantation didn't happen, the corpus luteum fades, progesterone drops, and the uterine lining sheds -- your period.

How to fix a short luteal phase

Since progesterone is what keeps your period from starting too soon, treating with progesterone is a common medical approach -- typically vaginal suppositories starting 3 days past ovulation. But are there natural ways to support progesterone before involving a doctor? Here's what the evidence says about the three most commonly discussed options.

Vitamin C

Background: Many women with unexplained infertility have lower antioxidant status, and vitamin C is a primary antioxidant present in high concentrations in the ovaries. Animal studies suggest ascorbic acid protects ovarian cells from oxidative damage -- and with less vitamin C, the corpus luteum can break down faster.

The claim: enough vitamin C in the reproductive system supports the luteal phase, implantation, and embryo development.

Evidence in favor: a small 1977 study found 400mg of daily ascorbic acid enhanced the ovulation-inducing effects of clomiphene in women who weren't ovulating regularly. A 2003 Japanese study found women given vitamin C had higher progesterone levels and a higher pregnancy rate (25% vs. 11%). An IVF study also linked vitamin C supplementation to a somewhat higher pregnancy rate (34% vs. 24%).

Evidence against: a larger, higher-quality 2001 study found supplementing with vitamin C during the luteal phase, across a range of doses, did not help women get pregnant.

What it means: the evidence isn't particularly strong, especially for supplementation limited to the luteal phase alone. That said, a vitamin C supplement or vitamin-C-rich foods (bell peppers, for instance) earlier in the cycle is still reasonable -- just don't overdo very large doses.

Selenium (Brazil nuts)

Background: selenium is essential for thyroid hormone synthesis and is a powerful antioxidant, found in high amounts in Brazil nuts. A deficiency is linked to male-factor infertility and higher risk of pre-eclampsia and preterm labor, and low selenium has also been associated with a shorter luteal phase.

The claim: selenium's antioxidant properties can help prolong the luteal phase.

Evidence in favor: plasma selenium levels correlate with higher luteal-phase progesterone. In one large study, women consuming twice the recommended daily selenium had a 77% lower risk of luteal phase deficiency. Among men, selenium supplementation has been linked to higher sperm count and quality.

What it means: there isn't a lot of high-quality research specifically on selenium and short luteal phases, but what exists is encouraging.

Vitex (chasteberry)

Background: Vitex is a popular alternative-medicine option, mostly used for PMS symptoms, that some believe lengthens the luteal phase. Real evidence is limited, and it can disrupt hormone balance and cycle regularity -- always talk to a doctor before considering it.

The claim: excess prolactin can suppress sex hormones; Vitex lowers prolactin and is said to indirectly boost fertility.

Evidence in favor: a small German study of 37 women with high prolactin found 20mg of daily Vitex reduced prolactin, prolonged the luteal phase by 5 days, and normalized luteal-phase progesterone. Other small, older studies suggest possible benefits for cycle regularity in women with very irregular cycles.

Evidence against: animal studies found no improvement in fertility or litter size. Female baboons that ate large amounts of a related Vitex plant species actually had trouble conceiving -- the progesterone spike acted as a natural contraceptive.

What it means: in women with diagnosed high prolactin, supplementation might restore a normal luteal phase length. Outside of that, evidence is thin, and side effects (nausea, interactions with birth control or hormone therapy, delayed ovulation) are real enough that it's worth a conversation with your doctor first.

So what should you do?

Vitamin C: a supplement or vitamin-C-rich foods may help through antioxidant properties -- start earlier in the cycle rather than waiting for the luteal phase.

Selenium: evidence is limited but encouraging for lengthening the luteal phase and supporting progesterone; don't overdo Brazil nuts, since selenium is toxic at high doses.

Vitex: reasonable only if you've been diagnosed with high prolactin -- otherwise the evidence doesn't clearly support it, and it carries real risk of disrupting your cycle.

The easy way: multivitamins

If you'd rather not track individual supplements, a good prenatal multivitamin covers a lot of this ground at once, including vitamin C and selenium alongside folate and omega-3s.

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And while you're at it, it's worth stocking up on reliable pregnancy tests that can detect a positive earlier than most (more on why that matters here).

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Progesterone suppositories

If your luteal phase is consistently short (under 10 days), talk to your doctor -- progesterone suppositories have a solid track record for lengthening the luteal phase and boosting progesterone levels directly.

References

Vitamin C:

1. Polak G, Koziol-Montewka M, Gogacz M, et al. Eur J Obstet Gynecol Reprod Biol 2001;94:261–263.
2. Behrman HR, Preston SL. Endocrinology 1990;127:245–250.
3. Igarashi M. Int J Fertil 1977;22(3):168–173.
4. Henmi et al. Fert Ster, 80(2), 459–461.

Selenium:

1. Hawkes WC, Turek PJ. J Androl, 2001, 22(5):764–72.
2. Safarinejad MR, Safarinejad S. J Urol, 2009, 181(2):741–51.
3. Rayman MP, Bode P, Redman CWG. Am J Obstet Gynecol, 2003, 189(5):1343–9.
4. Andrews MA, Schliep KC, Wactawski-Wende J, et al. Human Reproduction, 2015, 30(8), 1942–1951.

Vitex:

1. Milewicz A, Gejdel E, Sworen H, et al. Arzneimittel-forschung. 1993, 43(7):752–756.
2. Gerhard I, Patek A, Monga B, et al. Res Compl Med. 1998;5(6):272–278.
3. Higham JP, Ross C, Warren Y, et al. Hormones and Behavior. 2007, 52, 384–390.