A Fresh Look at Ovarian Hyperstimulation Syndrome (OHSS)

Dr. Geoffrey Sher - December 22, 2016
A Fresh Look at Ovarian Hyperstimulation Syndrome (OHSS)

Ovarian hyperstimulation syndrome (OHSS) is a life-endangering condition that occurs following ovarian stimulation for the treatment of infertility. It occurs due to overstimulation of the ovaries with the development of numerous follicles in susceptible women. Systemic effects can be very serious and can lead to life-endangering complications. Thus every effort must be made to avoid the condition and when it does threaten, to take the necessary steps to mitigate its effects, and at the same time attempt to protect egg quality which often is adversely affected as well. Prevention starts with recognizing those women who are at the greatest risk of developing OHSS. They include:

  • Those with a history of having hyperstimulated on fertility drugs in the past.
  • Younger women (<25y)
  • Women who have biochemical indicators that suggest they are so at risk of developing OHSS (e.g. An AMH of >5ng/ml; basal FSH of <5MIU/ml; basal LH level being significantly higher than LH; Antral follicle count of >25)
  • Women who have dysfunctional or absent ovulation.
  • Women diagnosed with Polycystic Ovarian Syndrome (PCOS)

In such cases, it is prudent to minimize the dosage of gonadotropins administered, but alas, this often will not eliminate risk of OHSS developing anyway. Aside from the risk that OHSS places the woman at, it can also have a devastating effect on egg quality/competency. Thus, all too often, the measures taken (see below) to reduce maternal risk come at a price. PRESENTATION AND MANAGEMENT OF OHSS: The onset of OHSS, heralded by the presence of large numbers  (>25) of developing ovarian follicles and rapidly rising plasma estradiol levels, often exceeding 3000pg/ml within 7 or 9 days of stimulation, and rapidly peaking above 6,000 pg/ml prior to hCG administration. When this happens, the risk of OHSS developing is above 80%.  The fear of this escalating often leads physicians to prematurely administer hCG in an attempt to abruptly arrest the process and prevent escalation of risk to the patient. However, the premature administration of the “trigger” shot arrests egg development and adds to the problem of poor egg/embryo quality in such cases. Symptoms and signs of OHSS include: abdominal distention due to fluid collection (ascites), fluid in the chest cavity (hydrothorax), rapid weight gain (of a pound or more per day) due to tissue fluid retention, abdominal pain, lower back ache, nausea, diarrhea, vomiting, visual disturbances such as blurred vision and spots in front of the eyes (scotomata), a rapidly declining urine output, cardiovascular collapse and failure of blood to clot which sometimes results in severe bruising (ecchymosis) and frank bleeding.  These symptoms and signs may appear before pregnancy can be diagnosed. If pregnancy occurs, the condition is likely to worsen progressively over a period of 3-5 weeks whereupon it rapidly resolves spontaneously over a few days. If no pregnancy occurs, the symptoms and signs all disappear spontaneously within 10-12 days of the hCG injection. When increasing fluid collection in the abdominal cavity (ascites) starts to compromise breathing raising the head of the bed rose slightly by placing a 4-6 inch block at the base of each head post and using a few additional pillows, will sometimes help ameliorate the problem. In cases where this does not help or symptoms become severe, all or most of the fluid can readily and safely be drained through t transvaginal sterile needle aspiration (vaginal paracentesis-performed once or sometimes twice a week) can be performed once or twice weekly . The problem will usually self corrects within 10-12 days of the hCG shot if pregnancy does not occur or, by the 8th week of pregnancy. Urine output should be monitored daily to see if it drops below about 500ml a day (about two cups and a half). A chest X-ray, to evaluate for fluid collection in the chest and around the heart should be done weekly along with blood tests for hematocrit, BUN, electrolytes, creatinine, platelet count and fibrin split products (FSP). If indicated on the basis of a deteriorating clinical situation, hospitalization might be needed for close observation and if necessary, to provide intensive care. In all case of OHSS, the ovaries and contain numerous theca-lutein cysts and will invariably be considerably enlarged. This is irrelevant to the final outcome, unless ovarian torsion (twisting of the ovary on its axis), an extremely rare complication occurs. The latter would usually require surgical emergency surgical intervention. Human chorionic gonadotropin (hCG) “Fans the flames “ of OHSS. That is why the occurrence of pregnancy worsens the condition. In women who do not conceive, the clinical severity of OHSS will usually peak 7-10 days after the hCG “trigger”, plateaus for another 3-4 days  and thereupon rapidly improves within the ensuing week. Thus in the absence of hCG the condition is “self-limited”. Sometimes severe symptoms due ascites make it imperative to drain the fluid transvaginally (often repeatedly). This brings immediate relief but it can be short-lived requiring repeated drainage a few days later until the condition resolves. If the woman conceives following a fresh embryo transfer, the rising hCG blood levels can exacerbate the OHSS for several weeks, but either way, it usually disappears spontaneously by the 8th to 9th harrowing week of pregnancy. This is why there is a growing tendency to avoid fresh embryo transfers, preferring to do FET’s later once the woman is out of risk. It is also the reason for a move to avoid using 10,000U of hCG for the “trigger shot” or to avoid to supplant hCG with an “agonist” trigger. But this comes at a price – see below.  OHSS AND POOR EGG/EMBRYO QUALITY/COMPETENCY: OHSS is also associated with poor egg/embryo quality. This is especially so in women with high ovarian LH-induced testosterone (e.g. those with PCOS). These often present with poorly developed (“dysmorphic”) eggs, with reduced fertilization potential and yielding “poor quality embryos”. However, in the author’s opinion (which admittedly runs contrary to popular opinion), this is unlikely to be due to an intrinsic deficit in egg quality. Rather, it more likely relates to   intra-ovarian hormonal changes brought about by hyperstimulation and which compromise egg development. This effect, in my opinion, can often be significantly reduced through implementation of an individualized or customized ovarian stimulation protocols that minimize exposure of the developing follicles and eggs to excessive LH-induced ovarian androgens. This can be best achieved by limiting the use of LH-containing gonadotropins such as Menopur through selective institution of “prolonged coasting" (see below). Approaches to preventing OHSS include:

  1. PROLONGED COASTING (My preferred approach) : My approach is to use a long pituitary DR protocol coming off up to 2 months on the BCP, overlapped in the last 3 days with the agonist, Lupron. The BCP is intended to lower LH and thereby reduce stromal activation (hyperthecosis) in the hope of controlling ovarian androgen (predominantly, testosterone) production and release. I then stimulate with low dosage FSHr (Follistim/Gonal-F/Puregon) to which I add a smidgeon of LH/hCG (Luveris/Menopur) from the 3rd day. Then, starting on day 7 of ovarian stimulation, I perform serial blood estradiol (E2) and ultrasound follicle assessments, watching for the number of follicles and [E2]. If there are > 25 follicles, I keep stimulating (regardless of the [E2] until 50% of all follicles reach 14mm. At this point, provided the [E2] reaches at least >2,500pg/ml, I stop the agonist as well as gonadotropin stimulation and track the blood E2 (without continuing US, follicle measurements) ) daily. The [E2] will almost invariably increase for a few days.  I watch the E2 rise (regardless of how high a blood concentration it reaches) and then track it coming down again. As soon as the [E2] drops below 2500pg/ml (and not before then), I administer a “trigger” shot of 10,000U hCGu (Profasi/ Novarel/Pregnyl) or hCGr (Ovidrel/Ovitrel-500mcg) and perform an egg retrieval 36 hours later. ICSI is a MUST because “coasted” eggs usually have no cumulus oophoris envelopment and eggs without a cumulus will not readily fertilize naturally. Moreover, they also tend to have a “hardened” envelopment (zona pellucida), making spontaneous fertilization problematic in many cases.  All fertilized eggs are cultured to blastocyst (up to 6 days) and are then either vitrified and preserved for subsequent transfer in later hormone replacement cycles or up to two (2) fresh blastocysts are transferred transvaginal under US guidance.. The success of this approach depends on precise timing of the initiation and conclusion of “prolonged coasting”. If you start too early, follicle growth will stop and the cycle will be lost. If you start too late, you will encounter too many post-mature/cystic follicles (>22mm) that usually harbor abnormally developed eggs.  Use of “Coasting” avoids unnecessary cycle cancellation, severe OHSS, and optimizes egg/embryo quality. The worst you will encounter is mild to moderate OHSS and this too is uncommon. The obvious remedy for these adverse effects on egg and endometrial development is to employ stimulation protocols that limit ovarian over-exposure to LH and allowing the time necessary for the follicles/eggs to develop optimally, prior to administering hCG through the judicious implementation of   “Prolonged coasting" (PC).
  2. MULTIPLE FOLLICLE ASPIRATION: In some cases, where because of mean follicle size exceeding 16mm or when “coasting” fails to effectively lower the [E2} below 2,500pg/ml within 3 days, the number of developing follicles can effectively and drastically reduced through target transvaginal aspiration, 1-3 PRIOR to planned the hCG trigger. This will almost invariably be accompanied by a rapid and significant drop in the plasma [E2] and in the process will drastically reduce reduce the risk of OHSS occurring without significantly compromising egg/embryo quality.  The drawback of this effective approach is the fact that it interjects an additional surgical intervention into an already complex and stressful situation.
  3. TRIGGERING WITH LOW DOISAGE hCG; Because of the fact that hCG augments the development of OHSS (unless preceded by “coasting”), may RE’s prefer to use a lower dosage of hCG for the “trigger." This is either done by administering 5,000U (half the traditional dosage) or by administering, a 250mcg (rather than 500mcg) of DNA recombinant form of hCGr (Ovidrel/Ovitrel. Some clinicians, when faced with a risk of OHSS developing will deliberately elect to  reduce the "trigger" dosage of hCG administered (from 10,000U to 5,000U or 250mcg of recombinant hCG-Ovidrel) in the hope that by doing so  the  risk of critical OHSS developing will be lowered.  While this might indeed be true, it is my opinion, that such a reduced dosage is usually insufficient to optimize the efficiency of egg meiosis, e3specially when there are so many follicles present. While the use of a reduced "trigger" dosage of hCG does indeed reduce the risk and occurrence of OHSS-related life-endangering complications, the price to be paid is reduced egg quality/"competency".
  4. “TRIGGERING” WITH A GnRH AGONIST (E.G. LUPRON/BUSERELIN): More recently, an increasing number of RE’s prefer to trigger meiosis by way of an agonist (Lupron/Buserelin/Superfact) "trigger" rather than through the use of hCG.  The idea is to mimic what happens in natural cycles to promote egg maturation (meiosis) and ovulation, namely to have the agonist cause a "surge" in the release of body's own pituitary LH to trigger egg meiosis (maturation) .But the amount of LH released in by the pituitary gland is often insufficient to optimize meiotic egg maturation and thus, while this approach also lowers the risk of OHSS it again comes at the expense of egg quality/competency.

A word of caution: I do not use long term administration of antagonists (Ganirelix/Cetrotide/Orgalutron), such as with the agonist/antagonist conversion protocol (A/ACP) in high responders whom are at risk of developing OHSS prolonged in-cycle administration of  because it can interferes with the E2  assay (often causing the value to be understated), and serial measurement of E2 is a vital part of monitoring patients undergoing “coasting”

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