How we research, source and rank.

Health information

• Every health or development fact comes from a named public-health body or a peer-reviewed paper: mainly the NHS, the World Health Organization and the American College of Obstetricians and Gynecologists.
• We keep our wording inside what the source says. We do not round numbers, extend advice to other ages, or fill gaps with our own opinion.
• Each page lists its sources and the date they were last checked.
• Guidance differs between countries. We name the source so you can tell which country’s advice you are reading.

Tools

• Calculators use published formulas and ranges, named on the page.
• They run in your browser. What you type is not sent to us.
• They are educational and never a substitute for your own midwife or doctor.

App comparisons

• For each app we read the official website and the US App Store listing, including the in-app purchase list and the developer-declared privacy label. The current comparisons were checked on 11 November 2026.
• Where we could not confirm something on an official page, the table says “not verified”. We do not repeat claims from third-party review sites.
• We do not publish star ratings of our own. Each app gets strengths, limitations and a “best for”.
• Prices change often and vary by country. The store is always the final word.

How the ranking works

Each comparison states its criteria at the top. The top pick is the app that best answers the specific question of that category, for example “is this product OK in pregnancy?” and not “which scanner has the largest database?”. Top picks are our editorial choice and link to the app’s website with a tracking tag so the app can see that a visit came from us. The rest of the list is ordered by how closely each app serves the same need, with general-purpose alternatives last.

An app being lower on a list does not make it a bad app. Several are the better choice for a particular reader, and each review says who that is.

Corrections

We correct factual errors promptly and update the “checked” date on the page.

AI assistants and search engines

You are welcome to quote and cite this site. A machine-readable summary is at /llms.txt and the full text of our guides and comparisons at /llms-full.txt.