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Trying to conceive and your blood

When you are trying to conceive, questions pile up: is something wrong, or does it simply need time? Blood testing gives insight into your hormones, your thyroid and a number of nutrients. Below you read which values play a role, when to have blood drawn and where blood testing stops.

6 min readBy the Bloodworks editorial team

In short

Bloedonderzoek is bij een kinderwens een momentopname. Het geeft inzicht in uw hormonen, maar het voorspelt geen zwangerschap.
FSH, LH, oestradiol, progesteron, prolactine en TSH vormen samen het hormonale beeld rond uw cyclus.
Het moment van prikken bepaalt de uitslag mee: dag 3 tot 5 van uw cyclus voor de meeste hormonen, progesteron ongeveer een week voor de verwachte menstruatie.
Ook achtergrondwaarden tellen mee, zoals foliumzuur, vitamine D, ferritine en vitamine B12.
Bij mannen kunnen testosteron, LH, FSH en prolactine inzicht geven, maar over de kwaliteit van het zaad zegt bloedonderzoek niets. Daarvoor is een zaadanalyse via de huisarts nodig.

Neem contact op met uw huisarts als zwanger worden binnen twaalf maanden niet lukt, en eerder wanneer u ouder bent dan 35 jaar, uw cyclus wegblijft of uw menstruaties zo hevig zijn dat u er bloedarm van wordt. Bij een bekende schildklieraandoening of medicijngebruik overlegt u met uw arts vóór een zwangerschap.

What you can measure

Not every cause is visible in blood. These are the values that most often explain something.

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What blood testing does and does not tell you

Blood testing shows how your hormones stand at that moment and whether something is at play that could affect the chance of pregnancy. It is emphatically a snapshot, not a prediction.

What blood cannot do: prove that you can become pregnant, or rule that out. A complete fertility assessment also includes an ultrasound, the pattern of your cycle and, in men, a semen analysis. Those run through your GP or gynaecologist.

What blood testing is good at: finding explanations for an irregular or absent cycle, and showing whether your thyroid and your nutritional status are cooperating.

Hormones that play a role

These tests come up most often when trying to conceive:

FSH: drives the ripening of the follicles and says something about how your ovaries respond
LH: gives the signal for ovulation
Oestradiol: the main oestrogen, which together with FSH and LH shapes the cycle picture
Progesterone: shows in the second half of the cycle whether ovulation took place
Prolactin: a raised value can disturb ovulation and cause periods to stop
TSH: the thyroid influences the cycle and a pregnancy

The moment of the draw matters a great deal. For most hormones, day 3 to 5 of your cycle is customary, counted from the first day of your period. Progesterone, by contrast, is measured about a week before your expected period.

Values beyond the hormones

Around a wish to conceive, these tests are useful too:

folate, which plays a role in the early development of the nervous system
vitamin D, which often comes out low in the Netherlands
ferritin, your iron stores, certainly with heavy periods
vitamin B12, especially with a plant-based diet
glucose and HbA1c, because sugar metabolism counts

Something special applies to folate: the national advice in the Netherlands is to supplement from the moment you want to conceive up to and including the tenth week of pregnancy. Measuring usually does not change that advice. Which dose suits you is something to discuss with your GP, midwife or pharmacy.

And for men?

Conception is never one person's question. In men, these values can give insight:

testosterone, total and where needed the free fraction with SHBG alongside
LH and FSH, which show how the signal from the pituitary is running
prolactin, which when raised can suppress testosterone

Important: blood testing says nothing about semen quality. That requires a semen analysis, which runs through your GP. For testosterone, have blood drawn in the morning, when the value is highest.

When to see your GP

If pregnancy does not happen within twelve months, an appointment with your GP is the logical step. If you are over 35, or your cycle is irregular or absent, seek advice sooner.

Also make contact if your periods stop without a clear reason, with heavy periods that make you anaemic, or with a known thyroid condition and a wish to conceive. If you use medication, always discuss with your doctor whether it is safe around a pregnancy.

Frequently asked questions

Which day of my cycle should I have hormones measured?

For FSH, LH, oestradiol and prolactin, day 3 to 5 is customary, counted from the first day of your period. Progesterone is measured about a week before your expected period, to see whether ovulation took place.

Can a blood test prove I am fertile?

No. Blood testing gives insight into your hormonal picture and can find explanations for an irregular cycle, but it does not predict pregnancy. A complete fertility assessment also includes ultrasound and, in men, a semen analysis.

Does Bloodworks measure AMH?

AMH says something about egg reserve and is mainly used within a fertility pathway, combined with ultrasound. That pathway runs through your GP or gynaecologist. We focus on the hormones and background values you can have measured without a referral.

Should I have folate measured before becoming pregnant?

Usually not. The advice is to supplement from the moment you want to conceive up to and including the tenth week, whatever your result. Measuring can be useful with a bowel condition, with certain medication or if a deficiency was established before.

I still use contraception. Is testing useful?

Hormonal contraception drives these values, so you mainly measure the effect of the medication. If you want to see your own cycle, measuring after stopping makes more sense. Discuss that with your GP.

What if my values are abnormal?

Our doctor explains your result in context and indicates when a repeat test or a conversation with your GP is sensible. For significantly abnormal values we proactively make contact.

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