Fertility Treatment and Breastfeeding

Infertility and fertility treatment can be a long, challenging and emotional journey for all the family. Many sacrifices and hard decisions come with each experience. Breastfeeding may be important to you, as something that was your choice, that was successful for you or was the part of your journey that you had autonomy and control over. The information below is provided to empower you to make informed decisions with your healthcare provider.

Around 1 in 7 couples experience difficulties in conceiving. Infertility is defined as when a couple cannot become pregnant, even though they are having regular (every 2-3 days), unprotected vaginal sex. More than 8 out of 10 couples trying to conceive through vaginal sex (where the mother or birthing parent is under 40) will become pregnant within one year and more than 9 out of 10 will become pregnant within 2 years.

If you’ve been trying to get pregnant through regular unprotected vaginal sex for one year, your doctor will be able to discuss next steps to refer you and your partner or review your reproductive health. You can see a doctor before a year has passed, you don’t have to wait. If you’re over 36 years of age, or you or your partner have any known causes of infertility or known history that may affect your fertility (including cancer), you can always speak to your doctor sooner or at the beginning of your journey.

The NHS- Infertility webpage has a lot of useful information on infertility, and treatments. You may find reading this with your partner useful as soon as you are starting to think about infertility.

You may access fertility treatment due to infertility, or as a single parent, a same sex couple who need sperm donation, or other LGBT community family who need assistance to conceive. You may experience different barriers and challenges in accessing fertility care. You can find out about your commissioned fertility services in your local area through your Integrated Care Board (ICB) in England, Strategic Planning and Performance Group (SPPG) in Northern Ireland, or Health Boards in Scotland and Wales. These health commissioners will have fertility policies including fertility preservation and information on criteria for access to services.

If you can’t access fertility treatments via the NHS due to gaps in commissioning or not meeting criteria, you may access private healthcare for your fertility treatment.

This factsheet shares information about breastfeeding whilst taking the most common medications used in both NHS and private UK clinics, as well as some of the supplements that you may use, depending on your type of treatment. It is not a guideline on treatment choices. All decisions should be made in partnership with your specialist, so you know your medicines are suitable for you and are evidence based. Clinics abroad may use different medications to those approved for use in UK clinics and The Drugs in Breastmilk service is unfortunately not able to comment on these as we only have access to resources on medicines used in the UK.

Some medications don’t easily enter breastmilk and so are low risk whilst breastfeeding. Others do reach your milk, but the level of risk they pose depends on the age of your breastfed child and how much milk they are drinking. These medications are less likely to affect an older child who is drinking less milk, as the amount of medicine they will receive through milk will be less. However, some fertility drugs remain unsafe whatever the age of your child and are not compatible with breastfeeding. These are discussed below.

If you are planning your next pregnancy and you have any long-term health conditions, you should speak to your doctor before you start trying to become pregnant so your medication can be reviewed for safety, and suitability during pregnancy. Your doctor can also advise on necessary supplements (including folic acid and vitamin D, discussed below.)

This is a very complex area and there is little research on fertility treatment while breastfeeding. Information is based on limited evidence, professional judgement, and knowledge of drug behaviour and effects in the body. You may find your healthcare professional advises you to stop breastfeeding before commencing treatment due to lack of evidence available to them or unfounded concerns about breastfeeding bringing on early labour. This factsheet presents key information and considerations you can discuss with your health care professional and partner (if you have one) when deciding what is right for your family.

Please contact the Drugs in Breastmilk team through their Facebook page or on druginformation@breastfeedingnetwork.org.uk  if you have questions about medicines not listed below.

If you are planning to become pregnant, you should take

Colecalciferol as a vitamin D supplement of 10micrograms once daily, starting 3 months before conception (if possible), throughout your pregnancy and until you finish breastfeeding.

• Vitamin D is compatible with breastfeeding at usual daily recommended doses, including doses discussed on the NHS page Pregnancy, breastfeeding and fertility while taking colecalciferol

Folic acid 400micrograms once daily. You should take folic acid starting 3 months before conception (if possible) until at least 12 weeks of pregnancy.

• Some people need a higher dose of folic acid while trying to conceive, and for the first 12 weeks of pregnancy. Some people may need it during the full pregnancy. Higher dose folic acid is 5mg once daily. Your healthcare professional will advise you if this applies to you.
• Folic acid is compatible with breastfeeding at both standard and higher doses
• The NHS page Pregnancy, breastfeeding and fertility while taking folic acid provides more information on folic acid.

Breastmilk or first infant formula is the sole source of nutrition for babies under 6 months and it remains their main source of energy and nutrition until around 12 months of age. If your baby is under 12 months of age and you are planning fertility treatment and pregnancy, you’ll need a plan to maintain your baby’s milk intake if your supply reduces. It is usual for your milk supply to change during pregnancy. You will usually experience reduced supply by mid pregnancy, but some will experience this earlier. This change happens due to the increased levels of estrogen and progesterone which are produced while you are pregnant. Some medications taken during your fertility treatment can also reduce your supply. Information on this is shared below.

Child over a year old? Two years old or beyond? While breastmilk continues to provide important nutrition into toddlerhood, including 29% of their energy needs and 94% of their vitamin B12 requirements, amongst other key nutrients, children over one year and beyond are no longer so reliant on your milk for their nutritional and energy needs. A drop in your milk supply may therefore be less of a concern if your child is over one. The volume of milk they consume after one year slowly reduces, as their intake of other foods increases, until they wean from breastfeeding. Breastfeeding isn’t just about the nutrition though. It provides comfort and regulation, as an important a part of the parenting toolbox. Many mums and breastfeeding parents continue to breastfeed through their pregnancy by dry nursing (nursing even when little or no milk is produced) and then go on to tandem feed (feed both the new baby and older child) when the new baby arrives.

If you need breastfeeding support, please contact the National Breastfeeding Helpline.

You may take fertility drugs to stimulate ovulation if you are having difficulty becoming pregnant due to polycystic ovarian syndrome (PCOS) or other conditions affecting ovulation, including hyperprolactinaemia (which may be caused by the pituitary gland), or irregular and unpredictable cycles.

Intrauterine insemination (IUI) is when sperm are introduced directly into your uterus. You might use fertility drugs alongside IUI. IUI is commonly used when you are using donated sperm in your treatment.

IVF treatment is where fertilisation happens outside your body. There are different types of IVF. Usually, you will receive medication to stimulate your ovaries to produce several eggs, which are collected. The eggs are then mixed with sperm to fertilise them into embryos. If your egg(s) are successfully fertilised, the embryos are allowed to develop before the strongest embryo is selected to be transferred into your uterus (womb). If you have several good quality embryos, you may choose to have the remaining embryos frozen for the future.

One IVF cycle can take 4-6 weeks, but the journey to starting a cycle can take some time and several appointments.

Some variations in IVF methods include but are not limited to:

Natural cycle IVF –  no fertility drugs are used to stimulate your ovaries. Your egg released during your usual cycle is collected before being mixed with sperm to fertilise the egg. This is not currently recommended by NICE, the national guidelines that informs NHS services on current practice. One cycle could take around 3 weeks as there are fewer stages for this type of cycle.

Mild stimulation IVF –  a lower dose of fertility drugs than usual is used to stimulate your ovaries.

In vitro maturation (IVM) – This new treatment may be used if you are also having ICSI (see below). In IVM, you won’t be given drugs to mature your eggs before they’re collected. Your eggs are collected while they’re immature and allowed to mature in the laboratory, where ICSI is then performed. Because IVM is new, there is less experience on its outcomes.

Intracytoplasmic sperm injection (ICSI) – May be used when the sperm quality is affected by low motility, or it is low in numbers. A single sperm is injected into the collected egg by your specialist to fertilise the egg.

Freeze All Cycle – May be used if you wish to start the process of fertility treatment but are not ready for pregnancy yet. Instead of transferring any embryos, they are all frozen to save for later.

Frozen Embryo Transfer (FET) – May be possible if you have frozen embryo(s) from a previous fertility cycle, or if you are using a donor embryo. During FET, your donated/saved embryo(s) are thawed ready for transfer into your uterus. While you will still need medication to prepare your uterus to receive your embryo, this process has fewer steps than a full IVF cycle as your ovaries don’t need to be stimulated for egg retrieval.

Reciprocal IVF – Is becoming more common for same-sex partnerships, where one partner provides the egg (they may be called the biological mother/parent in clinical guidelines), which is then fertilised using donor sperm and implanted into the uterus of the gestational mother/partner, allowing both to participate in the creation and development of their child. In this case, each partner will require different medicines, depending on their role in the process. This process may also be used if you are giving or receiving the gift of surrogacy.

You may have fertility drugs to stimulate your ovaries so that your eggs can be collected for donation to someone else.

Letrozole (as own brand, Femara^®) is an aromatase inhibitor drug used in IVF cycles to induce ovulation. Aromatase inhibitors work by blocking the enzyme aromatase, which converts other hormones to estrogen. Reducing estrogen levels is expected to improve IVF success by improving follicle growth in your ovaries.

Letrozole is not compatible with breastfeeding because it is expected to enter your milk in high enough amounts to affect your breastfed child.

Letrozole works reversibly. This means once it has left your body, your aromatase enzymes go back to working as usual and your estrogen levels will return to normal.

• It takes around 10 days for the majority of letrozole to leave your body, which would mean not breastfeeding until 10 days after your last dose.
• If you wish to continue breastfeeding after taking letrozole, it is recommended that you express and discard your milk while taking letrozole, and for 10 further days after your last dose of letrozole, before you return to feeding as usual.
• A course of letrozole may mean choosing to end your breastfeeding journey. You may be close to doing so anyway and feel comfortable or accepting of this. However, it could bring real feelings of grief if it’s earlier than you might have otherwise chosen to stop. You can contact the National Breastfeeding Helpline if you want to talk about these feelings though. See the section on stopping breastfeeding below for more information.
• For more information, see the NHS page Pregnancy, breastfeeding and fertility while taking letrozole.

Tamoxifen (as own brand) is a selective estrogen receptor modulator (SERM). It is an anti-estrogen drug. It prevents estrogen from reaching its receptors so estrogen cannot work at its target. In IVF, tamoxifen prepares the lining of your uterus for better embryo implantation and can stimulate the release of eggs from your ovaries, increasing the number of eggs available.

Tamoxifen is not compatible with breastfeeding.

• Tamoxifen reduces prolactin levels. This is expected to reduce your milk supply, even if it is well established.
• Tamoxifen can take up to 100 days to completely leave your system after your final dose.
• Tamoxifen is likely to enter your milk in adequate amounts to affect your baby’s estrogen balance.
• A course of tamoxifen may mean choosing to end your breastfeeding journey. You may be close to doing so anyway and feel comfortable or accepting of this. However, it could bring real feelings of grief if it’s earlier than you might have otherwise chosen to stop. You can contact the National Breastfeeding Helpline if you want to talk about these feelings. See the section on stopping breastfeeding below for more information.

Aspirin (as own brand), low dose, 75-150mg daily. Aspirin is used in IVF to improve the chances of successful implantation. It may also be used during pregnancy to reduce other risk factors such as low birth weight, or pre-eclampsia if you are at risk of these conditions.

Low dose aspirin can be taken with caution while breastfeeding (SPS). There is concern over a theoretical risk of Reye’s Syndrome, which a small number of children have developed when given aspirin directly whilst they had a temperature. The risk by breastmilk is theoretical, and Reye’s syndrome has not been observed in children with a temperature and exposure to aspirin via breastmilk in practice. SPS advise that if your breastfed child develops a fever, you can temporarily stop taking aspirin if safe to do or temporarily withhold breastmilk that contains aspirin.

Aspirin at higher doses for pain relief is not compatible with breastfeeding. See our factsheet on pain relief for more information.

For more information, see the NHS page Pregnancy, breastfeeding and fertility while taking low dose aspirin.

Clomifene (as Clomid^®, spelt “clomiphene” in the US) is a selective estrogen receptor modulator. It has both anti-estrogenic and estrogenic effects. It stimulates the release of follicle stimulating hormone (FSH) and luteinising hormone (LH) and lowers prolactin levels, resulting in ovulation and the release of mature egg(s).

Clomifene may be used with caution while breastfeeding.

• There is very limited evidence of the use of clomifene in lactation. Repeated cycles could lead to increased exposure to your child and reduced milk supply. This should be discussed with your specialist who can contact services including medicines information services for evidence-based information.
• Milk levels are expected to be relatively low, but it could be in your system for up to 35 days after your last dose.

Clomifene can reduce your prolactin levels, which might cause your milk supply to drop, particularly if you are feeding a young baby. This is a significant consideration if your baby is under one year of age.

Metformin (as own brand and various manufacturer brands) is a medication usually used to treat type 2 diabetes. It lowers blood sugar levels by improving how insulin works in your body.

Metformin may be used in people with polycystic ovary syndrome (PCOS) to improve their fertility. The brand Glucophage^® is now licenced for use in PCOS. Metformin may also be used during IVF cycles.

Metformin is compatible with pregnancy and breastfeeding.

For more information, see the NHS website Pregnancy, breastfeeding and fertility while taking metformin.

hCG is a hormone produced by the placenta during pregnancy. Synthetic hCG is used to stimulate ovulation during IVF.

Choriogonadotropin alfa injection (as Ovitrelle^®) and Chorionic gonadotrophin injection (as Zivafert^®) are synthetic forms of hCG.

hCG is compatible with breastfeeding.

• The hCG molecule is very large so only very small amounts, if any, would be expected to get into your milk. As it is made of protein, any that does pass into your milk will be broken down in your child’s stomach and would not be expected to have any effect on them.
• No adverse effects have been reported in breastfed children.

hCG might increase your prolactin levels, causing an unexpected increase in your milk supply.

FSH is a hormone released in the pituitary gland of your brain in response to another hormone called Gonadotropin-releasing hormone (GnRH). FSH triggers follicle growth in your ovaries before an egg is released.

FSH is compatible with breastfeeding.

• FSH is a large protein molecule. This means it does not get into breastmilk easily. Any that does get into your breastmilk will be broken down in your child’s stomach and would not be expected to have any effect on them.
• No adverse effects have been reported in breastfed children.

FSH is available in different forms including:

• Follitropin Alfa (as Gonal-F^®, Ovaleap^®, Bemfola^®, Pergoveris^®)
• Follitropin delta (as Rekovelle^®)
• Urofollitropin (as Fostimon^®)

It is likely your milk supply will reduce. This is particularly relevant if your child is under one year.

Menotrophin (as Menopur^®, Meriofert^®, Menogon^®) is a combination product containing both FSH and lutenising hormone (LH).

Menotrophin is compatible with breastfeeding.

• Menotrophin is a large molecule. Due to its size, it is not expected to enter your milk easily. Any that is present in your milk will be broken down in your child’s stomach and would not be expected to have any effect on them.
• No adverse effects have been reported in breastfed children.

It is possible your milk supply could reduce. This is particularly relevant if your child is under one year.

Steroids are hormones that suppress your body’s immune responses. They may be used in fertility treatment to help reduce inflammation and increase the chance of an embryo implanting.

Hydrocortisone (as own brand, Solu-Cortef^®) is naturally occurring in breastmilk.

Hydrocortisone is compatible with breastfeeding.

Hydrocortisone levels in your bloodstream and breastmilk are low. It clears from your system within 10-15 hours.

No adverse effects have been reported in breastfed children. High doses (>200mg) or longer courses could increase your child’s exposure to the medication. In this event, your child may need closer monitoring. Doses up to 160mg daily are unlikely to cause side effects to your child.

High doses may temporarily reduce your milk supply.

Prednisolone (as own brand)

Prednisolone is compatible with breastfeeding at usual doses of up to 40mg per day. Higher doses are rarely needed.

At this level, amounts of prednisolone in breastmilk are low. It clears from your system within 5-10 hours.

No adverse effects have been reported in breastfed children.

Medium to high doses given by injection may cause a temporary decrease in your milk supply.

If you are taking over 40mg daily or a long course of prednisolone, this may increase your child’s exposure to prednisolone. Your child may need additional monitoring which your healthcare professional will advise you on if it’s necessary (SPS).

Monitor your child for adequate feeding and weight gain.

You can find more information in our factsheet on prednisolone.

Prasterone (as own brand capsules/ tablets or DHEA tablets/ capsules) is a bioidentical form of dehydroepiandrosterone (DHEA), a naturally occurring steroid in the body which converts to testosterone and estrogen. Your levels naturally peak between your 20s and 30s, before slowly declining over time and through menopause.

While low levels of DHEA are associated with reduced ovarian reserve (fewer remaining eggs), high levels are also associated with negative effects on fertility. There is a lack of evidence on DHEA in fertility and more research is needed.

DHEA is not included in infertility guidelines in the UK; however, it is being discussed more.

DHEA transforms to estrogen and has been shown to reduce breastmilk supply without affecting prolactin levels.

DHEA has been shown to significantly lower HDL (good cholesterol) levels. If you have raised cholesterol levels, lowering HDL levels could have a negative impact on LDL and triglycerides (“bad” cholesterol). If you have problems with your cholesterol, you should discuss this with your doctor.

It is not clear if DHEA may increase androgens (testosterone) in breastmilk. This could cause side effects in your child.

There is no evidence for use of DHEA while breastfeeding.

Until more research is available, DHEA cannot be recommended while breastfeeding.

After ovulation and during early pregnancy (the first 10 weeks) your body secretes progesterone from the ovary that released the egg (known as the corpus luteum), to maintain your pregnancy. From around 10 weeks, your placenta takes over production of the majority of progesterone. During IVF, you will need to take progesterone supplements to increase the chance of successful implantation and maintain early pregnancy. 

Progesterone is available as Cyclogest^® pessaries, Lutigest^® vaginal tablets, Crinone^® vaginal gel, Utrogestan^® oral capsules and vaginal pessaries, Gepretix^® oral capsules, Lubion^® injection.

Progesterone is compatible with breastfeeding.

Progestogens are the recommended hormonal contraception option when breastfeeding. They are not expected to affect your milk supply once it is established (usually from 6-8 weeks after birth). 

The combined contraceptive pill, containing estrogen and a progestogen, may be used to time your cycle during IVF. It may also be used to induce a period if you have not had one in a while, or if your cycle hasn’t returned.

The combined pill is considered compatible with breastfeeding from 6 weeks after your baby is born.

Some people may experience a reduction in milk supply when they take the combined pill. If the combined pill affects your supply, this could be significant if your child is under one year of age.

You can find out more information on the combined pill when used for contraception on the NHS webpage The combined pill, and in our factsheet contraception and breastfeeding.

Estrogen is a naturally occuring hormone. Estrogen levels increase significantly throughout pregnancy, peaking in the third trimester before dropping significantly after delivery.

Estrogen is available in several forms including:

• Estradiol (body similar) transdermal (as Oestrogel^®, Evorel^® patches).
• Estradiol hemihydrate
  • Transdermal (as Estraderm^® patches, Estradot^® patches, FemSeven^® patches, Lenzetto^® spray, progynova^® TS patches, Sandrena^® gel)
  • Oral (as Zumenon^®, Elleste^® Solo)
• Estradiol valerate oral (as Progynova^® tablets)

Estradiol is often used to thicken the lining of your uterus to prepare it for a successful embryo transfer.

Estrogen is compatible with breastfeeding, regardless of the sex of your breastfed child.

Estrogen may reduce your milk supply. This could be significant if your child is under one year of age.

During a menstrual cycle, luteinising hormone (LH) surges to trigger ovulation. If you are undergoing egg collection, either GnRH agonists or antagonists will be used to prevent a natural LH surge, to avoid ovulation before scheduled egg collection. GnRH agonists and GnRH antagonists work in different ways to prevent an LH surge. GnRH agonists may also be used for egg maturation and to trigger ovulation.

These drugs are all large protein hormone molecules. This means they do not get into breastmilk easily. Any that does get into your breastmilk will be broken down in your child’s stomach and would not be expected to have any effect on them.

GnRH Agonists

Goserelin (as Zoladex^®), Leuprorelin (as Staladex^®, Prostap^®), Nafarelin (as Synarel^® nasal spray), Triptorelin (as Decapeptyl^®, Gonapeptyl^® Depot, Savacyl^®)

There is no published data for the use of goserelin, leuprorelin, nafarelin or triptorelin while breastfeeding.

Your prolactin levels may be increased during treatment which could cause an unexpected increase in your milk supply.

While increased prolactin levels have been observed in some individuals receiving GnRH agonists, your prolactin levels may also be significantly reduced which could reduce your milk supply. This is more likely while you are establishing your supply (usually the first 6-8 weeks after birth) but is still an important consideration if your supply is established or your child is older. If your supply decreases, this could be significant if your child is under one year of age.

Caution is recommended until more information is available on the effect of these medications on milk supply.

Buserelin (as generic injection, Supracur^® nasal spray, Suprafact^® injection)

Buserelin has been found to pass into breastmilk in very small to undetectable amounts. In limited studies it has not been found to cause side effects in breastfed infants.

Your prolactin levels may be increased during treatment which could cause an unexpected increase in your milk supply.

The possibility of buserelin causing a decrease in supply cannot be ruled out.  A decrease in your supply could be significant if your child is under one year old.

Caution is recommended until further data is available.

GnRH Antagonists

While these drugs are large protein hormone molecules, which means they do not get into breastmilk easily, they do last in the body a long time, which increases the likelihood of them reaching your milk. If these medications enter your breastmilk, they will be broken down in your child’s stomach and would not be expected to have any effect on your child. However, due to their long life in your body, you may prefer an alternative.

Cetrorelix (as Cetrotide^®), and Ganirelix (as own brand, Ovamex^®, Fyremadel^® injections)

There is no published data for the use of cetrorelix or ganirelix while breastfeeding.

Cetrorelix and ganirelix have a relatively long half-life which means they stay in your body for a long time.

Alternatives which leave your body more quickly may be preferred.

Dopamine agonists may be used when high prolactin levels are affecting ovulation. They may also be used to prevent ovarian hyperstimulation syndrome. They are potent breastmilk suppressors and have been used to quickly reduce and stop breastmilk supply.

Dopamine agonists include bromocriptine and cabergoline.

Both bromocriptine and cabergoline are incompatible with uncontrolled high blood pressure (hypertension). They have been associated with stroke and maternal death when given postnatally. This may be a consideration if you are at higher risk of high blood pressure, stroke or other heart disease (MHRA).

While bromocriptine and cabergoline are not unsafe if present in breastmilk, they will reduce your milk supply. This is significant if your baby is under one year of age.

Use of dopamine agonists during IVF aren’t expected to affect your milk coming in for your subsequent baby.