Fertility Levels by Age: Health Checks for Your 20s to 40s

If you came here feeling a little anxious about a number, that's common, and we'd gently suggest that a number about a whole population says very little about one woman. What helps more at this stage is knowing your own baseline. These are the years when periods, contraception, training, work and perhaps pregnancy all compete for attention, and routine checks slip quietly down the list. Most of them are quick, and several can be done at home, so there is usually a handful that suit your life right now.

What do fertility levels by age look like in real numbers?

Among US women who have not had a baby, the share reporting difficulty getting pregnant rises from 9.2% at ages 15–29 to 22.2% at 30–39 and 33.4% at 40–49, according to the CDC's National Survey of Family Growth, 2015 to 2019. The table below uses that survey measure, called impaired fecundity, which means difficulty getting pregnant or carrying a pregnancy to a live birth. Because it counts reported experience, it is not a biological fertility rate, and it works best as a rough guide to groups of women rather than a statement about you.

Across the three bands, the share reporting difficulty climbs, yet in every band most women report none. That is why the evidence supports planning with your age in mind without treating any birthday as a deadline.

Age is one part of the picture, and regular ovulation is another. Learning your menstrual cycle phases is a good place to start if you'd like to know what your own cycle is doing. If you already keep notes for training, our guide to cycle syncing draws on the same record.

This page covers one stage. For the years before this one, there's health checks in puberty, and for the years after, our perimenopause test page picks up where this list ends. The full list across every stage sits in health checks for women.

Age group	Women with no births reporting impaired fecundity	How to read it
15–29	9.2%	Fewer than 1 in 10 report difficulty.
30–39	22.2%	More women report difficulty, and most still report none.
40–49	33.4%	About a third report difficulty, and most women still report none.

Check, when, what to look for

Check	When	What to look for	Guidance by country
Cervical screening	US: a Pap test every 3 years from 21; from 30, an HPV test every 5 years.	HPV or cell changes, picked up early.It takes a few minutes and is worth keeping up to date.	UK: from 25, every 5 years if HPV-negative; England moved from 3 to 5 years in July 2025.
Blood pressure	Every 3–5 years under 40; yearly from 40, if a reading has been raised, or if you're pregnant.	Under 120/80 is normal; 130/80 or above is high (US).Quick and painless, and checked at every antenatal appointment in pregnancy.	UK threshold for high: 140/90.
Waist measurement	Every few months at home.	Your own trend over time.Many women keep it as a private baseline alongside how they feel and what their body can do.	–
Iron (ferritin) and blood count	If periods are heavy, you're tired, or you're planning pregnancy.	Ferritin under 30 ng/mL means low stores.It's worth asking for ferritin by name alongside the blood count.	–
Vitamin D	If you're at risk: darker skin, covered skin or little time outdoors.	Under 20 ng/mL (50 nmol/L) is low.Worth asking about if you spend most of the day indoors.	UK: NHS advice is 10 mcg a day, and a supplement is worth considering from October to early March.
Thyroid (TSH)	If you have symptoms.	Tiredness, weight change or irregular periods are the usual prompts.Thyroid problems are much more common in women.	–
Cholesterol	From 20, every 4–6 years; more often with a family history.	LDL, HDL and triglycerides, with Lp(a) measured once.Earlier if a close relative had early heart disease.	–
Blood sugar (HbA1c)	Every 1–3 years after gestational diabetes, otherwise if you're at risk.	Under 5.7% (42 mmol/mol).PCOS and gestational diabetes both raise diabetes risk.	–
Pre-pregnancy check	Before trying to conceive.	Rubella and other vaccinations, your medicines and any long-term conditions.Some medicines need to change before pregnancy.	–
Vaccinations	HPV catch-up to 26; Tdap, flu and RSV (at 32–36 weeks) in pregnancy.	An up-to-date record.Pregnancy vaccines protect the baby in its first months.	–
Sexual health screen	With new partners.	Chlamydia, gonorrhea, HIV and syphilis.Free and confidential.	–
Family history	Once, then updated as relatives' health changes.	Breast, ovarian or bowel cancer in close relatives.It may mean earlier screening or genetic testing.	–
Skin, eyes and teeth	A yearly skin self-check, eyes every 2 years and the dentist as advised.	Anything new or changing.Easy to let slide in busy years, and gum disease is more common in pregnancy.	–
Mental health	Ongoing, especially around pregnancy.	Low mood, anxiety, or intrusive thoughts after birth.It's worth raising with your doctor, OB-GYN or midwife.	–
Strength and fitness	Every 3 months.	Squat, deadlift or push-up numbers; 5 km time.A record of what your body can do.	–

Which health checks help before trying for a baby?

A pre-pregnancy check, iron levels, a thyroid test if you have symptoms and a sexual health screen are the checks on this list that speak most directly to conception. The pre-pregnancy visit is also a natural moment to ask about folic acid: the CDC advises at least 400 mcg a day, starting at least 1 month before conception, usually through a prenatal vitamin (pregnancy vitamins, in UK terms). Many women use the same appointment to ask about staying active, and our page on exercise in pregnancy covers that.

Cycles themselves are a kind of health check. Pelvic pain or irregular cycles that persist are worth a referral, and our pages on endometriosis and PCOS explain what that referral is looking for.

Iron is the check that tiredness tends to hide. If a blood count comes back low, our page on iron deficiency anemia treatment sets out the options (the UK spelling is anaemia). Mood belongs here too: if your low days follow a pattern each cycle, it's worth describing to your doctor, and our page on PMDD explains one condition behind that pattern.

Bleeding matters, too. Heavy periods draw on your iron month after month, and if your cycles change earlier than you expected, our page on early menopause is there to read. If your periods are heavy, a ferritin test shows how much iron you have in reserve.

Which routine screenings belong in the reproductive years?

Cervical screening, blood pressure, cholesterol and a family history review are the routine screenings of these years. Breast screening has its own page, and the mammogram section there is a useful read, particularly because family history may mean earlier screening.

Two of these differ by country. The Pap smear, known in the UK as a smear test or cervical screening, starts at 21 in the US with a test every 3 years, then an HPV test every 5 years from 30. In the UK it starts from 25, every 5 years if HPV-negative, and England moved from 3 to 5 years in July 2025. The same goes for normal blood pressure for women: 130/80 or above counts as high in the US, and the UK threshold is 140/90, so it helps to know which one your result is being read against.

Blood tests are easy to bundle. You might ask about HbA1c and cholesterol at a well woman exam, and in the UK your GP is the usual starting point. Cholesterol is often first checked from 20, every 4 to 6 years, and HbA1c every 1 to 3 years after gestational diabetes.

It helps to arrive knowing what your relatives have had, because that shapes whether breast cancer genetic screening is worth discussing. A short conversation with a parent or aunt before the appointment is often all it takes.

Facts

Relative fertility is about half as high at age 40 as in the late 20s and early 30s. about 50% lower at 40

ASRM Practice Committee, Optimizing natural fertility: a committee opinion · 2021

Evaluation is advised after 12 months of trying without conception, or after 6 months for women aged 35 and over. In the UK, the NHS advises seeing a GP after 1 year, and sooner for women aged 36 and over. 12 months; 6 months at 35 or over (US); 1 year, sooner at 36 or over (UK)

ASRM Practice Committee, Optimizing natural fertility: a committee opinion (US); NHS, Infertility (UK) · 2021

Impaired fecundity among women with no births was 9.2% at 15–29, 22.2% at 30–39 and 33.4% at 40–49; women with one or more births stayed at roughly 12–15%. This is a survey measure, not a biological fertility rate. 9.2% / 22.2% / 33.4%; roughly 12–15% with one or more births

CDC NCHS, National Survey of Family Growth: Key Statistics, Infertility/Impaired fecundity · 2015–2019 data

Cervical screening: from 21, a Pap test every 3 years; from 30, an HPV test every 5 years. UK: from 25, every 5 years if HPV-negative; England changed from 3 to 5 years in July 2025. 21: every 3 years; 30: every 5 years (US); from 25, every 5 years (UK)

USPSTF, Cervical Cancer: Screening (final recommendation statement); NHS England, 2025: cervical screening interval change · 2018; 2025

Blood pressure: checked every 3–5 years under 40, and yearly from 40, if raised or if pregnant. Under 120/80 is normal and 130/80 or above is high in the US; the UK threshold is 140/90. <120/80 normal; ≥130/80 high (US); 140/90 (UK)

USPSTF: blood pressure screening · 2021

Cholesterol: from 20, every 4–6 years, more often with a family history; LDL, HDL and triglycerides, with Lp(a) once.

AHA · current page

Women who could become pregnant should take at least 400 mcg of folic acid daily, starting at least 1 month before conception. 400 mcg per day

CDC, About Folic Acid · current page

UK vitamin D advice is 10 mcg a day; people do not make enough from sunlight between October and early March, so a supplement is worth considering then. 10 mcg per day (UK)

NHS, Vitamin D · current page

Common questions

How long does it usually take to get pregnant?

Often sooner than people expect. The ASRM reports that about 80% of couples conceive within the first 6 months of trying. The NHS gives a similar picture over a longer window: more than 8 in 10 couples where the woman is under 40 conceive naturally within a year. A few months without a positive test is common and normal.

How common is it to have trouble getting pregnant?

More common than most conversations suggest. In CDC survey data from 2015 to 2019, 13.4% of US women aged 15 to 49 reported impaired fecundity, and infertility affected 8.5% of currently married women in that age range, about 2.4 million. If this is you, you are far from alone, and it's a fair reason to ask for help.

When should I see a doctor about fertility?

A good place to start is a primary care provider or OB-GYN in the US, or your GP in the UK. The NHS notes that infertility is usually diagnosed and treated after 2 years of regular unprotected sex, so an earlier visit is about starting the conversation. Irregular cycles or ongoing pelvic pain are reasons to ask sooner.

Does having had a baby change the picture?

In the CDC survey, it does. Among women who had already had one or more births, impaired fecundity stayed at roughly 12 to 15% across the age groups instead of climbing the way it did for women with no births. That describes a pattern across many women, so your own history and cycles still matter more.

Who do I ask for these checks?

In the US, a primary care provider or OB-GYN can order most of them. In the UK, your GP is the starting point, with a midwife once you're pregnant. Sexual health screens are free and confidential, so a sexual health clinic is an option if you'd rather not go through your usual doctor. Waist and strength checks are yours to do at home.

Do these checks change during pregnancy?

Yes, a few become more frequent. Blood pressure is taken at every prenatal appointment, called antenatal in the UK. Gum disease is more common in pregnancy, so a dental visit is worth booking early on. Your OB-GYN or midwife will also ask about your mood, and that question is a real invitation to answer honestly.

What should I bring to a pre-pregnancy check?

A list of every medicine and supplement you take, your vaccination record if you have one, and a few notes on any long-term condition. It also helps to ask relatives about family history beforehand. Booking the visit ahead of trying leaves time for a vaccine or a prescription change to be sorted out first.

Next steps

A good place to start is the table: you might mark the checks that are overdue, the ones that match a symptom you've noticed, and the ones tied to a plan such as pregnancy. From there, one appointment can often cover several at once, and writing your questions down beforehand helps the visit go further. If anything on the red flag list sounds familiar, that's worth a doctor's visit soon, without waiting for a routine slot. Everything else can move at your pace. Some women want every number, others prefer the few that answer a question they have today, and both are reasonable. You know your body, your history and your plans, so the list that fits is yours to choose: this is not one size fits all.

See a doctor promptly if you have

Not pregnant after 12 months of trying (6 months if you are 35 or over)
Lumps, skin changes or nipple changes
Low mood, anxiety or intrusive thoughts in pregnancy or after birth
Pelvic pain or irregular cycles that persist: ask for a referral

Fertility levels by age: the health checks worth having in your reproductive years