Missed Period After Unprotected Sex: Causes, Pregnancy Testing, and Next Steps

A late or missed period after unprotected intercourse warrants systematic evaluation.

Priority: Rule Out Pregnancy

• Urine hCG test: Sensitive >99% at day of expected menses. Test first-morning urine.
• If negative & period >1 week late: Repeat in 48h (hCG doubles ~48h in early pregnancy).
• If still negative: Serum quantitative hCG (detects <5 mIU/mL).

Common Non-Pregnancy Causes

When to See a Clinician

• ≥2 missed cycles (or ≥1 if previously regular)
• Positive hCG (confirm viability/location)
• Symptoms: severe pain, heavy bleeding, galactorrhea, hirsutism, acne, hot flashes
• Desire for conception (preconception counseling)

Initial Workup

hCG, TSH, prolactin, FSH/LH (day 2–3 if cycling), testosterone, DHEAS, pelvic ultrasound.

Do not assume pregnancy or dismiss it. Test first, then investigate.

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• Solo Sex & Relationships: Impact on Trust & Intimacy
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• Brown Vaginal Discharge: Causes, Significance, and When to See a Doctor
• Understanding ASCUS Pap Test Results: Causes & Next Steps
• Endometriosis and the Colon: Symptoms, Impact & Diagnosis
• Irregular Menstrual Cycles: 8‑Step Management Framework
• Obstetrics vs. Gynecology: Key Differences Explained
• Provera for Irregular Periods: Understanding Usage and Benefits
• Vulvar Dysplasia: Understanding Aldara Treatment and HPV Links
• Transvaginal Ultrasound After Pelvic Ultrasound: When and Why It's Recommended

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Category	Examples	Mechanism
Stress (physical/emotional)	Exams, grief, travel, illness	HPA axis → ↓ GnRH pulsatility → anovulation
Weight change	Rapid loss/gain, eating disorders, athletics	Leptin/adipokine disruption of HPG axis
Hormonal contraception	OCP start/stop, missed pills, IUD, implant, DMPA	Endometrial atrophy, anovulation
Endocrine disorders	PCOS (most common), thyroid (hypo/hyper), hyperprolactinemia	Anovulation, cycle irregularity
Medications	Antipsychotics, antidepressants, chemo, glucocorticoids	Various (prolactin, HPA, direct ovarian)
Perimenopause	Age 40–50	Declining ovarian reserve, erratic ovulation