Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles
npj Digital Medicine (2019)
https://www.nature.com/articles/s41746-019-0152-7
This large dataset analysis found the average menstrual cycle length was about 29.3 days, with significant variation across individuals and ages.

The timing of the fertile window in the menstrual cycle
BMJ (2000)
https://www.bmj.com/content/321/7271/1259

The normal menstrual cycle and the control of ovulation
Endotext
https://www.ncbi.nlm.nih.gov/books/NBK279054/

Variability in the phases of the menstrual cycle
Journal of Obstetric Gynecologic & Neonatal Nursing
https://pubmed.ncbi.nlm.nih.gov/16776507/

Menstrual cycle length variation by demographic characteristics
npj Digital Medicine (2023)
https://www.nature.com/articles/s41746-023-00848-1

Timing of sexual intercourse in relation to ovulation: effects on probability of conception
New England Journal of Medicine (1995). *This landmark study showed that conception occurs only during a six-day fertile window ending on ovulation day, with pregnancy probability ranging from about 10% five days before ovulation to about 33% on ovulation day.
https://www.nejm.org/doi/full/10.1056/NEJM199512073332301

Day-specific probabilities of clinical pregnancy
Human Reproduction
https://academic.oup.com/humrep/article/14/7/1835/2913463

Intercourse timing and probability of conception
Fertility & Sterility
https://pubmed.ncbi.nlm.nih.gov/11937120/

Time-to-pregnancy studies and fecundability
American Journal of Epidemiology
https://academic.oup.com/aje/article/150/3/284/79064

Diagnosis and management of infertility
JAMA (2021)
https://jamanetwork.com/journals/jama/fullarticle/2781763

Global prevalence of infertility
PLOS Medicine
https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1001356

Prevalence of infertility in the United States
Fertility and Sterility
https://pubmed.ncbi.nlm.nih.gov/23290741/

Anti-Müllerian hormone as a predictor of ovarian reserve
Human Reproduction Update
https://academic.oup.com/humupd/article/20/5/688/620422

Fertility awareness-based methods for women’s health and family planning
Frontiers in Medicine
https://www.frontiersin.org/articles/10.3389/fmed.2022.858977

Effectiveness of fertility awareness methods
Journal of Obstetric Gynecologic & Neonatal Nursing
https://pubmed.ncbi.nlm.nih.gov/22432462/

Apps and ovulation prediction accuracy
Current Medical Research & Opinion
https://pubmed.ncbi.nlm.nih.gov/29916098/

Role of LH and FSH in follicular development
Endocrine Reviews
https://academic.oup.com/edrv/article/23/2/141/2424110

Hormonal changes in reproductive aging
Endocrine Reviews
https://academic.oup.com/edrv/article/28/5/505/2355060

Endocrinology of the menstrual cycle
Endocrinology and Metabolism Clinics
https://pubmed.ncbi.nlm.nih.gov/26115680/

Epidemiology and causes of preterm birth
Lancet
https://www.sciencedirect.com/science/article/pii/S0140673608600324

Weight gain during pregnancy
National Academies Press
https://nap.nationalacademies.org/catalog/12584/weight-gain-during-pregnancy

Maternal health literacy and neonatal outcomes
BMC Pregnancy and Childbirth
https://bmcpregnancychildbirth.biomedcentral.com/articles/10.1186/s12884-023-05832-7

Breastfeeding in the 21st century: epidemiology, mechanisms, and lifelong effect
Lancet (2016)
https://www.sciencedirect.com/science/article/pii/S0140673615010247

Breastfeeding and health outcomes for the mother-infant dyad
Pediatric Clinics of North America
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3508512/

Breastfeeding and maternal health outcomes
Acta Paediatrica
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4670483/

Breastfeeding and reduced risk of sudden infant death syndrome
Pediatrics
https://pubmed.ncbi.nlm.nih.gov/21873781/

Infant sleep and safe sleep guidelines
Pediatrics (American Academy of Pediatrics)
https://publications.aap.org/pediatrics/article/138/5/e20162938/60366

Infant sleep patterns worldwide
Sleep Medicine
https://pubmed.ncbi.nlm.nih.gov/20138578/

Multiple pregnancy epidemiology and outcomes
Lancet
https://pubmed.ncbi.nlm.nih.gov/16085170/

Twin pregnancy outcomes
Obstetrics & Gynecology
https://pubmed.ncbi.nlm.nih.gov/17601896/Item description

Incidence of early pregnancy loss
New England Journal of Medicine
https://www.nejm.org/doi/full/10.1056/NEJM198807283190401

Conception and early pregnancy loss
New England Journal of Medicine
https://www.nejm.org/doi/full/10.1056/NEJM200307243490401