COVID-19 Pandemic Stress Affected Ovulation, Not Menstruation

Miriam E. Tucker

June 17, 2022

Disturbances in ovulation that didn't produce any actual changes in the menstrual cycle of women were extremely common during the first year of the COVID-19 pandemic and were linked to emotional stress, according to the findings of an "experiment of nature" that allowed for comparison with women a decade earlier.

Findings from two studies of reproductive-age women, one conducted in 2006-2008 and the other in 2020-2021, were presented by Jerilynn C. Prior, MD, at ENDO 2022: The Endocrine Society Annual Meeting.

The comparison of the two time periods yielded several novel findings. "I was taught in medical school that when women don't eat enough they lose their period. But what we now understand is there's a graded response to various stressors, acting through the hypothalamus in a common pathway. There is a gradation of disturbances, some of which are subclinical or not obvious," said Prior, professor of endocrinology and metabolism at the University of British Columbia, Vancouver, Canada.

Moreover, women's menstrual cycle lengths didn't differ across the two time periods, despite a dramatic 63% decrement in normal ovulatory function related to increased depression, anxiety, and outside stresses that the women reported in diaries.

"Assuming that regular cycles need normal ovulation is something we should just get out of our minds. It changes our concept about what's normal if we only know about the cycle length," she observed.

It will be critical going forward to see whether the ovulatory disturbances have resolved as the pandemic has shifted "because there's strong evidence that ovulatory disturbances, even with normal cycle length, are related to bone loss and some evidence it's related to early heart attacks, breast and endometrial cancers," Prior said during a press conference.

Asked to comment, session moderator Genevieve Neal-Perry, MD, PhD, told Medscape Medical News: "I think what we can take away is that stress itself is a modifier of the way the brain and the gonads communicate with each other, and that then has an impact on ovulatory function."

Neal-Perry noted that the association of stress and ovulatory disruption has been reported in various ways previously, but "clearly it doesn't affect everyone. What we don't know is who is most susceptible. There have been some studies showing a genetic predisposition and a genetic anomaly that actually makes them more susceptible to the impact of stress on the reproductive system."

But the lack of data on weight change in the study cohorts is a limitation. "To me one of the more important questions was what was going on with weight. Just looking at a static number doesn't tell you whether there were changes. We know that weight gain or weight loss can stress the reproductive axis," noted Neal-Parry of the department of obstetrics and gynecology at the University of North Carolina School of Medicine, Chapel Hill.

"Experiment of Nature" Revealed Invisible Effect of Pandemic Stress

The women in both cohorts of the Menstruation Ovulation Study (MOS) were healthy volunteers aged 19-35 years recruited from the metropolitan Vancouver region. All were menstruating monthly and none were taking hormonal birth control. Recruitment for the second cohort had begun just prior to the March 2020 COVID-19 pandemic lockdown.

Interviewer-administered questionnaires (CaMos) covering demographics, socioeconomic status, and reproductive history, and daily diaries kept by the women (menstrual cycle diary) were identical for both cohorts.

Assessments of ovulation differed for the two studies but were cross-validated. For the earlier time period, ovulation was assessed by a threefold increase in follicular-to-luteal urinary progesterone (PdG). For the pandemic-era study, the validated quantitative basal temperature (QBT) method was used.

There were 301 women in the earlier cohort and 125 during the pandemic. Both were an average age of about 29 years and had a body mass index of about 24.3 kg/m2 (within the normal range). The pandemic cohort was more racially/ethnically diverse than the earlier one and more in-line with recent census data.

More of the women were nulliparous during pandemic than earlier (92.7% vs 80.4%; P = .002).

The distribution of menstrual cycle lengths didn't differ, with both cohorts averaging about 30 days (P = .893). However, while 90% of the women in the earlier cohort ovulated normally, only 37% did during the pandemic, a highly significant difference (P < .0001).

Thus, during the pandemic, 63% of women had "silent ovulatory disturbances," either with short luteal phases after ovulation or no ovulation, compared with just 10% in the earlier cohort, "which is remarkable, unbelievable actually," Prior remarked.  

The difference wasn't explained by any of the demographic information collected either, including socioeconomic status, lifestyle, or reproductive history variables.

And it wasn't because of COVID-19 vaccination, as the vaccine wasn't available when most of the women were recruited, and of the 79 who were recruited during vaccine availability, only two received a COVID-19 vaccine during the study (and both had normal ovulation).

Employment Changes, Caring Responsibilities, and Worry Likely Causes

The information from the diaries was more revealing. Several diary components were far more common during the pandemic, including negative mood (feeling depressed or anxious, sleep problems, and outside stresses), self-worth, interest in sex, energy level, and appetite. All were significantly different between the two cohorts (P < .001) and between those with and without ovulatory disturbances.

"So menstrual cycle lengths and long cycles didn't differ, but there was a much higher prevalence of silent or subclinical ovulatory disturbances, and these were related to the increased stresses that women recorded in their diaries. This means that the estrogen levels were pretty close to normal but the progesterone levels were remarkably decreased," Prior said.

Interestingly, reported menstrual cramps were also significantly more common during the pandemic and associated with ovulatory disruption.

"That is a new observation because previously we've always thought that you needed to ovulate in order to even have cramps," she commented.

Asked whether COVID-19 itself might have played a role, Prior said no woman in the study tested positive for the virus or had long COVID.

"As far as I'm aware, it was the changes in employment...and caring for elders and worry about illness in somebody you loved that was related," she said.

Asked what she thinks the result would be if the study were conducted now, she said: "I don't know. We're still in a stressful time with inflation and not complete recovery, so probably the issue is still very present."

Prior and Neal-Perry have reported no relevant financial relationships.

ENDO 2022. Presented June 12, 2022.

Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape, with other work appearing in The Washington Post, NPR's Shots blog, and Diabetes Forecast magazine. She is on Twitter: @MiriamETucker.

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