The evidence library

Fertility advice is easy to find and hard to check. These pages are our attempt at the opposite: a small number of topics where every statement is shown next to the health authority document it came from, with the actual wording of that document beside it.

Where the evidence is thin, we say so on the statement rather than leaving it out and hoping you don't notice.

Endocrine Disruptors and Fertility: What the Evidence Says

What endocrine-disrupting chemicals are, where they turn up in ordinary households, and what health authorities have actually established about their effect on fertility. Every statement sourced.

7 sourced statements

Heavy Metals in Food and Water: Arsenic, Cadmium, Lead and Mercury

Arsenic in well water, cadmium in organ meats, lead exposure routes and mercury in fish, with the limits health authorities have set and the passages they set them in.

8 sourced statements

The Menstrual Cycle, Ovulation and the Fertile Window

How the menstrual cycle actually works, what happens at ovulation, when the fertile window falls, and when a pregnancy officially begins. Sourced to ASRM, NICHD and ACOG.

8 sourced statements

Folate and Choline Before Pregnancy: What the Guidelines Set

What folate and choline do, the intakes US health authorities publish for conception and pregnancy, why folic acid and food folate are not interchangeable, and where both nutrients occur in food.

13 sourced statements

B Vitamins and Fertility: B1, B6, B7 and B12

What thiamin, B6, biotin and B12 do, the deficiency signs authorities list, how B12 deficiency is detected, and why homocysteine keeps appearing in fertility research.

10 sourced statements

Zinc, Selenium and Manganese: Intakes, Upper Limits and Food Sources

The published intakes and upper limits for zinc, selenium and manganese, who is actually at risk of running low, and why plant sources of these minerals are absorbed differently.

12 sourced statements

Vitamin A and Retinoid Safety in Pregnancy

Why preformed vitamin A and beta-carotene carry different risks in pregnancy, the supplement ceiling authorities publish, topical retinoids, and where vitamins D, E, K and C sit alongside them.

10 sourced statements

Blood Sugar, Carbohydrates and Whole Grains Before Pregnancy

How carbohydrates become blood sugar, what actually blunts the rise, the difference between whole and refined grains, and what happens to insulin sensitivity in pregnancy.

13 sourced statements

Dietary Fats and How to Read a Label

What systematic reviews show about trans fats and fertility, why trans fats persist after the US ban, the ingredient words that reveal them, and where monounsaturated fat and full-fat dairy fit.

6 sourced statements

PCOS, Body Weight and Ovulatory Infertility

What ovulatory infertility is, why PCOS is its most common cause, what authorities say about body weight and fertility, and what the evidence on weight change actually supports.

7 sourced statements

What "sourced" means here

Each statement carries a label saying how strong its backing is: whether more than one authority states it, whether one authority's guidance states it, or whether a systematic review supports it. Those are different strengths and we show which is which.

None of these records has been through clinical review yet, and every one of them says so. That will change, and when it does the labels change with it.

The methods page sets out which authorities we check against and what we hold back, and the corrections page is how to tell us we've got something wrong.

Educational information, not medical advice.