7.3 Contraindications and Contraception

A Short List, Tested Hard

The whole of Pharmacology and Toxicology rewards restraint, and nowhere more than here. The IBCLC must hold a short, memorized list of true contraindications and recognize that almost everything else — mastitis, a cold, an L2 antibiotic, a needed antidepressant — is compatible. Exam items bury one real contraindication among several compatible conditions, or present a temporary/positional issue and tempt you to call it absolute.

True Contraindications

Group them into infant-side and maternal-side, and tag each as absolute, temporary, or positional.

Infant-side

• Classic galactosemia — the only infant metabolic absolute contraindication. The infant cannot metabolize galactose; since lactose is the main carbohydrate in human milk, the baby requires a galactose-free formula. (Some other inborn errors, e.g., PKU, allow partial breastfeeding with monitored levels — galactosemia does not.)

Maternal-side

• HIV — in high-resource settings such as the United States, maternal HIV without sustained viral suppression contraindicates breastfeeding because the virus transmits through milk. Context matters: where replacement feeding is not safe (many low-resource settings), the WHO supports breastfeeding on antiretroviral therapy because the danger of not breastfeeding is greater.
• HTLV-1 / HTLV-2 (human T-cell lymphotropic virus) — an absolute contraindication due to milk-borne transmission.
• Active, untreated tuberculosis — a temporary contraindication to direct breastfeeding (droplet transmission). After about 2 weeks of treatment and documented non-infectiousness, the mother may nurse; importantly, expressed milk can be given throughout because TB does not pass through milk itself.
• Active herpes (HSV) lesion on the breast — a positional restriction: feed from the unaffected breast and cover or avoid the lesion until healed.
• Certain chemotherapy / antimetabolites and radioactive isotopes — require temporary or permanent interruption; for a diagnostic radioisotope, the mother pumps and discards for the isotope-specific interval, then resumes.
• Active illicit drug use (cocaine, PCP, etc.) — a contraindication during use (covered in the substances section).

Most Conditions Are NOT Contraindications

For contrast, these common scenarios do not stop breastfeeding: mastitis (continue feeding/draining), most maternal infections (cold, flu, COVID with precautions), hepatitis B (with infant immunoprophylaxis) and hepatitis C, an L1-L3 medication, and a single screening X-ray or routine MRI/CT contrast. When the stem lists one of these, the answer is to continue.

Contraception During Lactation

Contraceptive counseling is a recurring exam theme because the wrong method can sabotage supply. The governing rule: estrogen can reduce milk supply, especially in the early weeks, so progestin-only or non-hormonal methods are preferred.

The LAM Criteria

LAM uses exclusive breastfeeding itself as contraception, and is about 98% effective — but only when all three conditions hold simultaneously:

1. The infant is under 6 months old.
2. The mother is amenorrheic (no menses returned after 56 days postpartum).
3. The mother is exclusively or nearly exclusively breastfeeding (frequent day and night feeds, no long gaps, minimal supplementation).

If any criterion fails — the baby turns 6 months, menses return, or feeds become spaced/supplemented — LAM is no longer reliable and a backup method is needed.

Worked Example: A mother at her 6-week visit is breastfeeding exclusively, has had no period, and wants reliable contraception while protecting supply. Her clinician suggests a combined estrogen-progestin pill. The IBCLC, collaborating with the prescriber, notes that estrogen can lower supply in these early weeks and that this mother could rely on LAM now (under 6 months, amenorrheic, exclusive) while transitioning to a progestin-only method, levonorgestrel IUD, or copper IUD before any LAM criterion lapses. This protects both contraceptive efficacy and milk supply.

In-Text Recap

Memorize the short contraindication list — galactosemia (infant), and HIV (context-dependent), HTLV-1/2, untreated TB until treated, breast herpes lesion, and certain chemo/radioisotopes (maternal) — and tag each as absolute, temporary, or positional. For contraception, prefer progestin-only or non-hormonal methods because estrogen can cut supply, and apply all three LAM criteria before relying on it.

Contraindication Classification