IVF Stimulation Phase: Days, Sex, Sleep, Red Flags

You are either holding your first stim kit on the kitchen counter, or you are three days into shots, bloated and sleepless, asking whether what you are feeling is normal or a phone call. This post is the walkthrough I wish every patient had before night one, including the unglamorous parts nobody puts on the clinic handout, like sex during IVF stimulation, sleep, work, and the small symptoms that send you spiralling at 11pm.

Why does the stim phase matter more than people realise?

The stimulation phase is short, usually 10 to 14 days, and it is where most of the cycle's medical decisions actually get made.¹ Protocol choice, starting dose, dose adjustments, trigger timing, trigger type, freeze-all versus fresh transfer: almost every consequential decision in an IVF cycle is finalised during this window. By the time you reach egg retrieval, the outcome of that retrieval has largely been set up over the previous fortnight.

Your body is also doing something it was never designed to do. In a natural cycle, the ovaries quietly ripen exactly one egg from a pool of fifteen to twenty antral follicles, and the rest are dismissed.² In stim, follicle-stimulating hormone (FSH) is given at a dose high enough to override that selection, so the whole cohort of follicles is recruited together. Ten, fifteen, twenty follicles growing in parallel is not subtle physiology. Almost everything you feel during stim (the bloating, the pressure, the mood swings, the sleep that gets worse every night) has a clean physiologic explanation. Knowing the explanation does not make the symptoms disappear, but it does lower the fear underneath them, and that is what most readers are looking for tonight.

The other thing I want to set up early: this post is broad on purpose. I will answer the specific questions readers most often search for, including sex during IVF stimulation, but the post is wider than any single query because the cycle is wider than any single query. You will be making small decisions every day for two weeks. The more of the system you understand, the less reactive each of those decisions has to be.

What is happening inside your ovaries during stim?

Each ovary at the start of a cycle holds a cohort of small antral follicles, typically two to nine millimetres across. Every follicle is a fluid-filled cyst containing one immature egg. In a non-treatment cycle, FSH from the pituitary rises just enough to support one of those follicles, and the others, deprived of the FSH they needed, undergo atresia and disappear. Stim works by replacing that physiological FSH with injected FSH at a much higher dose, plus sometimes injected luteinising hormone (LH) activity, so the cohort that would have been atretic is rescued and continues to grow.¹

Across stim, follicles enlarge by roughly one to two millimetres per day on average, though responders vary widely. Estradiol, the main oestrogen produced by granulosa cells inside the follicles, rises in parallel with follicle count and size. Levels of two thousand to four thousand picograms per millilitre on trigger day are common in a strong response.³ Above roughly five thousand, the risk of ovarian hyperstimulation syndrome (OHSS) climbs sharply, which is why your clinic watches estradiol nearly as closely as it watches follicle size.⁴

Two more drugs do important background work. The GnRH antagonist, usually Cetrotide or Ganirelix, is typically added on stim day five to seven. It prevents your pituitary from triggering its own LH surge before your follicles are ready.⁵ Without it, an early LH surge would cause your body to ovulate before retrieval and the cycle would be lost. The GnRH agonist (Lupron, leuprolide) does a related job in long protocols by first stimulating then suppressing the pituitary entirely, which is why those protocols start weeks earlier. The trigger shot, given at the end of stim, completes final maturation of the eggs. It times them precisely to retrieval thirty-five to thirty-six hours later.

What does each IVF stim injection do?

Stim usually involves three to four different injections running on overlapping schedules. The names are confusing because most have a brand name and a generic name and several countries' equivalents. I will group them by what they do.

The growth drivers are the gonadotropins. FSH-only products (Gonal-F, Follistim, Puregon, Bemfola) drive follicle development directly. They are subcutaneous, usually given in the evening, into the abdomen. FSH-plus-LH products (Menopur, Pergoveris) add LH-like activity, which helps in some poor responders and in patients with low endogenous LH. Menopur stings more than the FSH-only options, and that is a property of the medication, not a sign you are injecting wrong.

The surge suppressor in most modern cycles is the GnRH antagonist. Cetrotide and Ganirelix (sold as Orgalutran in some countries) block the pituitary's GnRH receptors and stop a premature LH surge.⁵ They are typically started on stim day five to seven, given subcutaneously in the morning or evening per clinic protocol, and continued daily until the trigger.

In long protocols, the suppressor is instead the GnRH agonist, Lupron. It is started in the mid-luteal phase of the previous cycle, suppresses the pituitary completely after an initial flare, and is continued through stim.

The trigger shot is its own category. It is timed to the minute, usually thirty-five to thirty-six hours before egg retrieval. The traditional trigger is human chorionic gonadotropin (hCG), sold as Ovidrel, Pregnyl, or Novarel. It mimics the LH surge and matures the eggs. Lupron trigger is used in antagonist cycles when OHSS risk is high. It gives a short physiological LH surge from the patient's own pituitary and is associated with near-zero OHSS risk.⁴ Dual trigger combines low-dose hCG with Lupron and is increasingly common.

The medication names are worth memorising in your kit because nurses speak in shorthand and you will hear yourself referred to as "the patient on Menopur and Ganirelix" rather than by name. That is not impersonal. It is how the rhythm of a clinic works.

What is the monitoring rhythm, day by day?

A typical antagonist cycle runs like this. On cycle day two or three you have a baseline scan to confirm the ovaries are quiet, with no functional cyst, and that your endometrium is thin. Bloods check that estradiol is suppressed at baseline. Stim starts that evening.

You will then come back for monitoring every two to three days through the rest of stim. Each visit includes a transvaginal scan and a blood draw. The sonographer counts and measures each follicle in each ovary. The bloods check estradiol, sometimes LH and progesterone.¹ The clinic uses two numbers together: how many follicles you have and how big they are getting (the scan), and how briskly your follicles are producing oestrogen (the bloods). A high follicle count with low estradiol may mean the response is starting slowly. A modest follicle count with sky-high estradiol may mean each follicle is overworking.

Dose adjustments happen on the back of these visits. High responders, often with polycystic ovary syndrome (PCOS), frequently get their daily FSH dose reduced after the first response check. Slow responders may have their dose increased and, less commonly, may have LH-activity added in. Trigger timing is decided when the two or three lead follicles reach about seventeen to twenty millimetres, with most of the cohort following close behind. Trigger night is set down to the minute, almost always thirty-five to thirty-six hours before retrieval.

In a long-agonist protocol, the stim portion looks similar, but you will have spent ten to fourteen days on Lupron alone before stim even started. In a microdose flare or mini-IVF cycle, the dose schedule and dose level are different, but the monitoring pattern is the same.

How many days is IVF stimulation, really?

The most common search I see for this phase is the simple one: how many days. The honest answer is that the stim phase itself, from first FSH injection to trigger, is usually ten to twelve days, with a normal range of eight to fourteen.¹ Some PCOS responders need fewer days because their follicles take off quickly; some poor responders need more days at higher doses. Add the antagonist days inside that window, the trigger shot at the end, and then thirty-five to thirty-six hours until retrieval, and the medication-heavy portion of the cycle lands at roughly two weeks from cycle day two.

If you are on a long-Lupron protocol, add another ten to fourteen days of down-regulation before stim, which is why those cycles feel three to four weeks long even though the stim portion is the same.

What does IVF stimulation feel like, day by day?

I tell my patients to expect a curve that runs roughly like this, though every body writes its own version.

Days one to three: usually you feel normal. Mild bloating may start. The injections themselves are the loudest thing, and most patients report that the anticipation was worse than the act.

Days four to six: bloating climbs and is now noticeable. Breast tenderness is common. Mood lability is real: irritation and tearfulness, often disproportionate, are an oestrogen effect, not a personal failure. Sleep starts to be interrupted, often by getting up to urinate as the ovaries press on the bladder.

Days seven to ten: your pelvis feels noticeably full. Bending at the waist is harder. You may feel an ache where your ovaries sit, left side, right side, or both. You may notice you can feel the ovaries themselves with your fingers if you press gently below the hip bones. Sleep is often the worst it gets: lying flat is uncomfortable, and most patients end up propped up with pillows or sleeping on their side with a pillow between their knees.

Trigger night to retrieval: ovaries are at their largest. In a high responder they can be the size of a small grapefruit each, sometimes a palm-sized organ where a walnut normally sits. Walk gently. No running. No twisting. No sex. We will come back to that.

A note on flu-like symptoms during IVF stimulation. Some patients report achiness, low-grade malaise, mild headache. This is usually the rising oestradiol load, sometimes the Menopur (which contains urinary-derived hormones and can be more inflammatory), and occasionally a simple coincidence of catching a cold during a two-week period when you are not sleeping well. True fever above 38°C is not stim. Call your clinic.

Can you have sex, sleep, and work during IVF stimulation?

These are the searches I see fill my analytics every week, and they are the questions you may not feel able to ask the on-call line. I am giving you my answer, but the final word on anything that worries you is your own clinic.

Can we have sex during IVF stimulation? Sex during IVF stimulation is the most-searched question in this phase, and the clean answer is: early stim, low risk; mid-to-late stim, no. In the first three or four days, when ovaries are still close to baseline size, intercourse is generally fine if it is comfortable. From around day five or six onward, as ovaries enlarge and become heavy, intercourse carries a real, though small, risk of ovarian torsion, the ovary twisting on its blood supply because it has become too large and too mobile for its ligaments.⁴ Torsion is a surgical emergency. It is rare, but the consequence is severe enough that most clinics advise abstaining for the back half of stim.

There is a second reason your clinic will mention. Unprotected sex during IVF stimulation can in theory produce a multifollicular spontaneous conception if the trigger fails or your body releases an egg before retrieval. The chance is low, but it is not zero, and the implications (a multifetal pregnancy following an unintended ovulation in a stim cycle) are serious enough to take the warning seriously. Use a condom or abstain.

Can you get pregnant during IVF stimulation? Yes, very rarely. The whole point of the antagonist or agonist is to stop you ovulating prematurely. If the suppression works and trigger is given properly, the eggs are retrieved in theatre. But before trigger, in a cohort of fifteen to twenty growing follicles, an unscheduled LH surge that gets past the suppression can produce ovulation. This is one of the reasons to take the surge-suppressing injection at the same time every day.

Is it normal to bleed during IVF stimulation? Light spotting can happen, especially around the time the antagonist starts, and is usually harmless. Heavier bleeding, fresh red bleeding that fills a pad, or bleeding with cramping needs to be discussed with your clinic the same day.

Can I take ibuprofen during IVF stimulation? I avoid non-steroidal anti-inflammatory drugs (NSAIDs) in stim and the days around retrieval, because they can interfere with follicle rupture, ovulation timing, and post-retrieval inflammation in ways that are unhelpful. Acetaminophen (paracetamol) is the preferred analgesic in this window. Always confirm with your own clinic.

Can I take a bath during IVF stimulation? Warm baths, yes. Very hot baths and hot tubs, avoid: partly for general pregnancy-considering caution, partly because vasodilation in a body with enlarging ovaries is not what we want.

Can you drink during IVF stimulation? I ask patients to skip alcohol for the stim phase and through retrieval. The evidence on small amounts is mixed, but the cycle is short, the stakes are high, and abstaining for two weeks is one of the few clean variables we can control.¹

How to sleep during IVF stimulation: Side sleeping with a pillow between the knees and another supporting the abdomen helps most patients past day seven. Sleeping slightly propped up reduces the pressure feeling. A small bedtime snack with protein can blunt the night-time hot flushes some patients get from rising oestrogen.

Can I work out? Walking is fine throughout. Running, twisting, jumping, heavy lifting, and core work I ask patients to stop from around day five onward, again because of torsion risk. Yoga that involves deep twists or inversions is the same: gentle and supported, yes; full practice, no.

Can I fly? Most clinics advise against air travel during stim and for the first week post-retrieval, both because of OHSS risk and torsion risk away from your treating clinic.

Can I work? Yes, usually. Plan to block out two to three hours every other morning for monitoring visits and bloods. By the back half of stim, plan that days will be heavy and concentration will slip. If you can, treat trigger day and the day after as effectively off.

What red flags during stim mean you should call the clinic?

Most of stim is uncomfortable, not dangerous. The list below is short, and any one of them is reason to call the on-call line rather than wait until the morning. I would rather take a midnight call and reassure you than meet you in the emergency department in the morning.

• Sudden weight gain of two kilograms or more in twenty-four hours.
• Severe one-sided pelvic pain, especially if it comes with nausea or vomiting. This can signal ovarian torsion.
• Shortness of breath, decreased urination, or abdominal swelling that limits walking or bending. These can be early signs of ovarian hyperstimulation syndrome.⁴
• Heavy red bleeding, fever above 38°C, or a rapidly spreading red, hot, swollen patch at any injection site.
• A calf that becomes swollen, painful, or red: concern for deep vein thrombosis, which carries a slightly higher risk in high-estradiol states.

Severe OHSS has become uncommon in well-managed cycles since the antagonist protocol and agonist trigger became standard.⁴ Uncommon is not the same as gone. PCOS readers, high-AMH readers, and any reader who has had OHSS before should know the symptoms cold and not wait.

What are the common first-cycle stim mistakes to avoid?

These are the small things that surface in clinic in the first week of stim, every cycle. None of them are catastrophic. All of them are avoidable.

1. Injecting at wildly different times day to day: Stim medications work best on a stable schedule, ideally within a two-hour window. The antagonist is the strictest: late or missed doses raise the risk of a premature LH surge, which can cancel a cycle. Set an alarm. Keep injecting at the same time even on weekends.
2. Skipping the antagonist because you "felt fine that day": The antagonist does not produce a feeling. Its absence does, by allowing an LH surge that ovulates your follicles before retrieval. Never skip.
3. Not refrigerating Menopur properly after mixing: Once reconstituted, mixed Menopur has limited stability outside refrigeration. Use it promptly after mixing.
4. Drawing back air and panicking: Small bubbles in a subcutaneous syringe are harmless. Larger ones can be gently flicked to the top of the barrel and expelled before injecting.
5. Not eating before injections: Lightheadedness during injection is almost always low blood sugar, not the medication. A small carbohydrate-and-protein snack twenty minutes before the dose prevents most of it.
6. Rotating sites too tightly: Alternate sides each dose, and within a side, move at least an inch from the previous site. Bruises accumulate if you stack injections.

If you make these mistakes, do not panic. Call your clinic in the morning. The cycle is more forgiving than the leaflet implies.

What should you ask at your next monitoring appointment?

You will see your nurse and possibly your reproductive endocrinologist (RE) every two to three days during stim. Most patients leave with no clear sense of how the cycle is actually going because nobody asked the right questions. These four are the ones I would prepare in advance:

1. What is my estradiol per mature follicle, and is the ratio where you would want it for my responder profile? A useful sanity check on whether each follicle is producing the expected oestrogen.
2. Has my dose been adjusted this cycle, and what triggered that decision? Knowing the dose history makes the next conversation easier if you ever do a second cycle.
3. What is the clinic's OHSS-prevention protocol if my estradiol passes four thousand picograms per millilitre or my follicle count passes twenty? Get the answer in advance, not in a panic.
4. Will I be triggered with hCG, Lupron, or dual trigger, and what would flip you between them?

If you have PCOS or a high AMH, add a fifth: what is the freeze-all threshold at this clinic, and at what point do we decide to skip a fresh transfer?

What comes after the stim phase?

After the questions about sex during IVF stimulation, sleep, and work are settled, the next decisions arrive in quick succession: trigger night and the thirty-five-to-thirty-six-hour window, retrieval day, the fertilisation report, and then the choice between fresh transfer and freeze-all. Where you go next depends on how stim ends.

What's next

• If you want to understand which protocol you are on and why your RE chose it: Common IVF Stim Protocols: Long, Short, Antagonist Explained
• If your injection technique is the part that still worries you: Injections in IVF: Self-Injecting and What to Expect
• If you have PCOS or a high AMH and want to understand your responder profile: Why PCOS Patients Get More Eggs and the OHSS Risk
• If you are watching for OHSS specifically: OHSS: Ovarian Hyperstimulation Syndrome and How Doctors Prevent It
• If your cycle is cancelled or does not lead to retrieval: When Things Don't Go to Plan

Sources

1. ESHRE Guideline Group on Ovarian Stimulation, Bosch E, et al. ESHRE guideline: ovarian stimulation for IVF/ICSI. Human Reproduction Open 2020;2020(2):hoaa009. https://doi.org/10.1093/hropen/hoaa009
2. La Marca A, Sunkara SK. Individualization of controlled ovarian stimulation in IVF using ovarian reserve markers: from theory to practice. Human Reproduction Update 2014;20(1):124-140. https://doi.org/10.1093/humupd/dmt037
3. Bosch E, Labarta E, Crespo J, et al. Circulating progesterone levels and ongoing pregnancy rates in controlled ovarian stimulation cycles for IVF: analysis of over 4,000 cycles. Human Reproduction 2010;25(8):2092-2100. https://doi.org/10.1093/humrep/deq125
4. Practice Committee of the American Society for Reproductive Medicine. Prevention and treatment of moderate and severe ovarian hyperstimulation syndrome: a guideline. Fertility and Sterility 2016;106(7):1634-1647. https://doi.org/10.1016/j.fertnstert.2016.08.048
5. Al-Inany HG, Youssef MA, Ayeleke RO, et al. Gonadotrophin-releasing hormone antagonists for assisted reproductive technology. Cochrane Database of Systematic Reviews 2016;4:CD001750. https://doi.org/10.1002/14651858.CD001750.pub4
6. Roque M, Lattes K, Serra S, et al. Fresh embryo transfer versus frozen embryo transfer in in vitro fertilization cycles: a systematic review and meta-analysis. Fertility and Sterility 2013;99(1):156-162. https://doi.org/10.1016/j.fertnstert.2012.09.003