Long-form, peer-reviewed-cited posts on cycles, fertility, pregnancy, PCOS, and body composition.https://hercalc.com/en-ushttps://hercalc.com/blog/weight-and-fertility-evidence/https://hercalc.com/blog/weight-and-fertility-evidence/The U-shaped fertility curve, why 5–10% weight changes can restore ovulation, BMI thresholds and time-to-conception, and when weight is and isn't the issue.Mon, 27 Apr 2026 00:00:00 GMTbodyhttps://hercalc.com/blog/safe-period-failure-rate/https://hercalc.com/blog/safe-period-failure-rate/Calendar-based fertility awareness has a 24% per-year typical-use failure rate. Here's the data, the math, and what to use instead if pregnancy prevention is the goal.Sat, 25 Apr 2026 00:00:00 GMTsafe-periodhttps://hercalc.com/blog/ultrasound-due-date-crl/https://hercalc.com/blog/ultrasound-due-date-crl/First-trimester ultrasound is the most accurate way to date pregnancy. Here's exactly how the CRL measurement becomes a due date — and when to trust it over your LMP.Wed, 22 Apr 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/bbt-vs-lh-vs-mucus-comparison/https://hercalc.com/blog/bbt-vs-lh-vs-mucus-comparison/How basal body temperature, LH tests, and cervical mucus actually compare for tracking ovulation: cost, accuracy, real-time vs retrospective, and when to combine them.Sun, 19 Apr 2026 00:00:00 GMTfertilityhttps://hercalc.com/blog/cycle-as-vital-sign/https://hercalc.com/blog/cycle-as-vital-sign/ACOG calls the menstrual cycle a vital sign. Here's how to read your own cycle data the way a clinician would — what counts as normal, what to flag, and what to bring to your next appointment.Sat, 18 Apr 2026 00:00:00 GMTcycle-healthhttps://hercalc.com/blog/pcos-cycle-tracking/https://hercalc.com/blog/pcos-cycle-tracking/Calendar-based cycle prediction routinely fails for PCOS users. Here is a practical, evidence-based playbook for tracking irregular cycles and identifying ovulation when textbook math gives up.Wed, 15 Apr 2026 00:00:00 GMTpcoshttps://hercalc.com/blog/bmi-women-context/https://hercalc.com/blog/bmi-women-context/BMI for women treats every body the same. Here's what the number actually measures, where it falls short, and the cardiometabolic context (WHR, WHtR, body fat) that gives a fuller picture.Sun, 12 Apr 2026 00:00:00 GMTbodyhttps://hercalc.com/blog/pcos-rotterdam-criteria-explained/https://hercalc.com/blog/pcos-rotterdam-criteria-explained/The Rotterdam 2003 criteria for PCOS, how AE-PCOS differs, what each criterion means in practice, and why PCOS diagnosis is genuinely hard.Sat, 11 Apr 2026 00:00:00 GMTpcoshttps://hercalc.com/blog/fertile-window-explained/https://hercalc.com/blog/fertile-window-explained/The fertile window is six days, not just one. Here's the Wilcox NEJM 1995 study, what each day means for conception probability, and why early-window timing matters more than people think.Wed, 08 Apr 2026 00:00:00 GMTfertilityhttps://hercalc.com/blog/pregnancy-symptoms-by-week/https://hercalc.com/blog/pregnancy-symptoms-by-week/A week-by-week guide to pregnancy symptoms from week 4 to week 40 — when each symptom appears, what causes it, and when to call your provider. Based on ACOG guidance.Wed, 08 Apr 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/twin-pregnancy-due-dates/https://hercalc.com/blog/twin-pregnancy-due-dates/Twin pregnancy gestational targets, ACOG guidance for monochorionic vs dichorionic twins, why 35–37 weeks is typical, and IOM weight gain ranges for twin pregnancies.Sun, 05 Apr 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/hypothalamic-amenorrhea-explained/https://hercalc.com/blog/hypothalamic-amenorrhea-explained/Hypothalamic amenorrhea causes missing periods through energy deficit, over-exercise, or stress. Learn how it differs from PCOS, how recovery works, and what it means for fertility.Thu, 02 Apr 2026 00:00:00 GMTcycle-healthhttps://hercalc.com/blog/waist-to-height-ratio/https://hercalc.com/blog/waist-to-height-ratio/Waist-to-height ratio predicts cardiovascular disease, diabetes, and mortality better than BMI. Learn the Ashwell 2012 evidence, how to measure correctly, and what each band means clinically.Sat, 28 Mar 2026 00:00:00 GMTbodyhttps://hercalc.com/blog/pcos-and-fertility/https://hercalc.com/blog/pcos-and-fertility/PCOS is the leading cause of anovulatory infertility. Learn how PCOS affects fertility, what labs to get, and how ovulation induction with letrozole or clomiphene works — with 2023 Monash guidance.Tue, 24 Mar 2026 00:00:00 GMTpcoshttps://hercalc.com/blog/pregnancy-test-timing/https://hercalc.com/blog/pregnancy-test-timing/When to take a home pregnancy test, hCG doubling rules, sensitivity differences between brands, and why the morning of your missed period is the safe bet.Sun, 22 Mar 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/first-trimester-what-to-expect/https://hercalc.com/blog/first-trimester-what-to-expect/What's developing in weeks 1–13, which symptoms are normal, when your first prenatal visit happens, and what NIPT involves — an honest, ACOG-grounded first trimester guide.Thu, 19 Mar 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/postpartum-period-return/https://hercalc.com/blog/postpartum-period-return/When your period returns after birth, how breastfeeding delays it, the LAM method's actual effectiveness, and when to be concerned about postpartum bleeding patterns.Tue, 17 Mar 2026 00:00:00 GMTcycle-healthhttps://hercalc.com/blog/bmi-vs-body-fat-percentage/https://hercalc.com/blog/bmi-vs-body-fat-percentage/BMI is a population-level screening tool, not an individual measure. Here is what body fat percentage adds, what 'skinny fat' really means, and which test is worth doing.Sun, 15 Mar 2026 00:00:00 GMTbodyhttps://hercalc.com/blog/ivf-due-date-explained/https://hercalc.com/blog/ivf-due-date-explained/IVF due dates are calculated differently than natural pregnancies. Learn the math for Day 3, Day 5, and Day 6 transfers — fresh and frozen — and why IVF dating is more accurate than ultrasound.Sat, 14 Mar 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/tracking-bbt-for-conception/https://hercalc.com/blog/tracking-bbt-for-conception/BBT charting confirms ovulation and reveals your cycle's true pattern. Learn the equipment, technique, and chart interpretation that make BBT useful for conception planning.Tue, 10 Mar 2026 00:00:00 GMTfertilityhttps://hercalc.com/blog/gestational-age-vs-fetal-age/https://hercalc.com/blog/gestational-age-vs-fetal-age/Why your provider says you are 8 weeks pregnant when conception was only 6 weeks ago. The LMP-based gestational age system, in plain language.Sun, 08 Mar 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/perimenopause-cycle-changes/https://hercalc.com/blog/perimenopause-cycle-changes/What happens to your cycle from age 35 onward, the STRAW+10 staging system, hormonal changes in perimenopause, and when irregular is normal vs concerning.Sun, 08 Mar 2026 00:00:00 GMTcycle-healthhttps://hercalc.com/blog/anovulation-and-irregular-cycles/https://hercalc.com/blog/anovulation-and-irregular-cycles/Anovulation means no egg is released, yet bleeding still occurs. Learn to recognize it, understand PCOS links, and know when to see a clinician. Evidence-based guidance.Thu, 05 Mar 2026 00:00:00 GMTpcoshttps://hercalc.com/blog/cervical-mucus-tracking/https://hercalc.com/blog/cervical-mucus-tracking/How cervical mucus changes through your cycle, what dry, sticky, creamy, and egg-white mean, and why mucus is the most accurate real-time marker of fertility.Tue, 03 Mar 2026 00:00:00 GMTfertilityhttps://hercalc.com/blog/amh-and-ovarian-reserve/https://hercalc.com/blog/amh-and-ovarian-reserve/AMH measures egg quantity, not quality. It does not predict natural fertility well. Here is what AMH means by age, and where it actually matters clinically.Mon, 02 Mar 2026 00:00:00 GMTfertilityhttps://hercalc.com/blog/miscarriage-rates-by-week/https://hercalc.com/blog/miscarriage-rates-by-week/A clear, gentle look at miscarriage probability by gestational week, why early ultrasound matters, and what an 80 percent risk reduction by week 8 really means.Wed, 25 Feb 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/stress-and-missed-periods/https://hercalc.com/blog/stress-and-missed-periods/Stress can delay or cancel ovulation through HPA axis suppression of GnRH. Here is when stress explains a missed period and when something else is going on.Thu, 19 Feb 2026 00:00:00 GMTcycle-healthhttps://hercalc.com/blog/thyroid-and-menstrual-cycles/https://hercalc.com/blog/thyroid-and-menstrual-cycles/Hypothyroidism and hyperthyroidism both shift menstrual cycles. Here is how each one changes your pattern, when to ask for a TSH, and what the labs mean.Sat, 14 Feb 2026 00:00:00 GMTcycle-healthhttps://hercalc.com/blog/endometriosis-and-cycles/https://hercalc.com/blog/endometriosis-and-cycles/Heavy painful periods are not normal. Endometriosis takes 7 to 10 years to diagnose on average. Here are the cycle patterns and red flags that should prompt earlier evaluation.Mon, 09 Feb 2026 00:00:00 GMTcycle-healthhttps://hercalc.com/blog/luteal-phase-defect-myth/https://hercalc.com/blog/luteal-phase-defect-myth/Luteal phase defect was once a routine infertility diagnosis. ASRM no longer considers it a clinical entity in most cases. Here is what the evidence actually shows.Wed, 04 Feb 2026 00:00:00 GMTfertilityhttps://hercalc.com/blog/waist-circumference-women/https://hercalc.com/blog/waist-circumference-women/How to measure waist correctly, WHO and IDF cutoffs (88cm general, 80cm for many Asian populations), and why visceral fat is the metabolic story.Fri, 30 Jan 2026 00:00:00 GMTbodyhttps://hercalc.com/blog/secondary-amenorrhea-causes/https://hercalc.com/blog/secondary-amenorrhea-causes/Workup for periods that stopped after being normal: pregnancy first, then PCOS, hypothalamic, thyroid, prolactin, and POI. When to refer.Tue, 27 Jan 2026 00:00:00 GMTcycle-healthhttps://hercalc.com/blog/heavy-menstrual-bleeding/https://hercalc.com/blog/heavy-menstrual-bleeding/Defining heavy menstrual bleeding with PBAC and product soak-through, iron-deficiency screening, and the evidence-based evaluation pathway.Sun, 25 Jan 2026 00:00:00 GMTcycle-healthhttps://hercalc.com/blog/pcos-and-mental-health/https://hercalc.com/blog/pcos-and-mental-health/Anxiety and depression rates are 3x higher in PCOS. The biology, the stigma, and what actually helps when both metabolic and mental symptoms overlap.Thu, 22 Jan 2026 00:00:00 GMTpcoshttps://hercalc.com/blog/pcos-and-insulin-resistance/https://hercalc.com/blog/pcos-and-insulin-resistance/How insulin resistance fuels PCOS hyperandrogenism, what HOMA-IR means, and the evidence for metformin and lifestyle interventions.Mon, 19 Jan 2026 00:00:00 GMTpcoshttps://hercalc.com/blog/prenatal-vitamins-evidence/https://hercalc.com/blog/prenatal-vitamins-evidence/Folic acid timing, iodine, DHA, iron, and the truth about premium prenatals. Evidence-based guidance on what to take and when.Sat, 17 Jan 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/gestational-diabetes-screening/https://hercalc.com/blog/gestational-diabetes-screening/GDM screening at 24-28 weeks, one-step vs two-step glucose tolerance testing, who needs early screening, and what the numbers mean.Wed, 14 Jan 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/labor-induction-when-and-why/https://hercalc.com/blog/labor-induction-when-and-why/Why labor is induced, what 39-week elective induction in low-risk pregnancy actually changes, Bishop score, and how to think about timing.Sun, 11 Jan 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/vbac-success-rates/https://hercalc.com/blog/vbac-success-rates/Vaginal birth after cesarean candidates, predictors of success, the MFMU calculator, and current ACOG guidance for safe trial of labor.Thu, 08 Jan 2026 00:00:00 GMTpregnancyhttps://hercalc.com/blog/group-b-strep-pregnancy/https://hercalc.com/blog/group-b-strep-pregnancy/GBS screening at 36-37 weeks, what a positive result means, intrapartum antibiotics, and current ACOG guidance for safer deliveries.Mon, 05 Jan 2026 00:00:00 GMTpregnancy