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Advanced Micromanipulation
Laser Assisted Hatching (LAH) is a precision micromanipulation technique performed in the IVF laboratory in which a highly controlled infrared laser beam creates a small opening in the zona pellucida, the outer shell of the embryo, immediately before embryo transfer. This assists the embryo in breaking free from its shell and implanting into the uterine lining. LAH is recommended for frozen-thawed embryos, embryos with a thick zona pellucida, patients with repeated implantation failure, and older patients. At Samarth IVF, LAH is performed using state-of-the-art diode laser systems by trained embryologists across our main centres in India.
Every embryo, from the moment of fertilisation through its development in the laboratory, is enclosed within a protective outer coat called the zona pellucida (ZP). The zona pellucida is a glycoprotein shell approximately 15 to 20 micrometres thick that surrounds the egg and the early embryo. It plays several critical roles during early development: it protects the embryo from physical damage, prevents polyspermy (fertilisation by more than one sperm), and keeps the dividing cells together as the embryo compacts into a morula and then expands into a blastocyst.
For implantation to occur, the blastocyst must break free from the zona pellucida entirely, a process called hatching. Hatching is driven by the expansion pressure of the growing blastocyst, assisted by enzymes secreted by the trophectoderm cells. The zona thins as it stretches and eventually ruptures, allowing the blastocyst to escape and make direct contact with the endometrial lining of the uterus. Only after hatching can the trophectoderm cells begin to invade the endometrium and establish the blood supply that will become the placenta.
The zona pellucida is composed of three glycoproteins: ZP1, ZP2, and ZP3. ZP3 is the primary receptor for sperm binding during fertilisation. After fertilisation, zona hardening (cortical reaction) occurs to prevent additional sperm from entering.
In freshly fertilised eggs and early embryos, zona pellucida thickness ranges from 15 to 20 micrometres. Variations outside this range may affect hatching.
In vitro culture conditions, cryopreservation (freezing and thawing), and patient age can alter zona pellucida properties, potentially making it thicker, harder, or less amenable to natural hatching.
LAH uses a highly controlled infrared diode laser integrated into the inverted microscope used by the embryologist. The laser emits a focused beam of infrared light that delivers a precise, brief pulse of thermal energy to a specific point on the zona pellucida. This creates a small, clean opening of approximately 10 to 20 micrometres in diameter without touching or damaging the embryo cells inside.
On the day of transfer, the embryologist assesses each embryo designated for LAH under the inverted microscope. The zona pellucida thickness, blastocoel expansion, and ICM and TE quality are evaluated.
The embryo is positioned using a holding pipette so that the intended site of laser application is away from the inner cell mass and positioned at the 3 o'clock or 9 o'clock position on the zona.
A single brief laser pulse of precisely calculated duration and power is directed at the zona pellucida at the chosen position. The pulse creates a clean opening of 10 to 20 micrometres.
The embryo is immediately assessed to confirm the opening is correct and that the embryo cells are undamaged. The embryo is returned to the incubator for a brief recovery period before transfer.
The embryo is loaded into the transfer catheter and transferred into the uterine cavity in the usual way under ultrasound guidance.
The entire LAH procedure takes approximately 2 to 5 minutes per embryo. It adds minimal time to the overall transfer process and does not delay or complicate the transfer procedure. The laser is controlled by computer software that precisely regulates the pulse duration and power to deliver consistent, reproducible results.
Three methods of assisted hatching have been described: mechanical hatching (using a fine glass needle to physically breach the zona), chemical hatching (using acidified Tyrode solution to dissolve a portion of the zona), and laser hatching. Laser hatching is now universally preferred because it is the most precise, the most reproducible, the fastest, and the safest. The laser creates a predictable, consistently sized opening at a precisely targeted location with no chemical exposure to the embryo and no risk of mechanical trauma from a physical needle.
LAH uses a highly controlled infrared diode laser integrated into the inverted microscope used by the embryologist. The laser emits a focused beam of infrared light that delivers a precise, brief pulse of thermal energy to a specific point on the zona pellucida. This creates a small, clean opening of approximately 10 to 20 micrometres in diameter without touching or damaging the embryo cells inside.
Cryopreservation can alter zona pellucida properties, making the zona thicker or less flexible after thawing. LAH is routinely recommended for frozen-thawed embryo transfers at Samarth IVF, particularly for cleavage-stage frozen embryos. Blastocysts approaching natural hatching at the time of transfer may not require LAH.
When the embryologist measures zona pellucida thickness above 15 to 17 micrometres on assessment before transfer, LAH is recommended to reduce the physical barrier to hatching.
Patients who have had 2 or more failed embryo transfers with good-quality embryos and no identifiable endometrial cause may benefit from LAH in a subsequent transfer cycle. LAH is one of several interventions considered in the investigation and management of unexplained RIF.
Older eggs and embryos may have thicker or more rigid zonae pellucidae. LAH may assist hatching in embryos from older patients where zona properties are more variable.
Older eggs and embryos may have thicker or more rigid zonae pellucidae. LAH may assist hatching in embryos from older patients where zona properties are more variable.
For embryos that are borderline in quality but still worthy of transfer, LAH may provide a marginal additional benefit by reducing one potential barrier to implantation.
Embryos that are slightly behind the expected developmental timetable on the day of transfer may benefit from LAH to reduce the energy expenditure required for natural hatching.
The evidence base for LAH is somewhat mixed across the broader literature, reflecting the fact that outcomes depend heavily on patient selection. When applied to patients with the specific indications listed above, particularly frozen-thawed embryos, thick zona, repeated implantation failure, and older patients, the evidence consistently supports a benefit from LAH.
Multiple systematic reviews and meta-analyses confirm that assisted hatching improves clinical pregnancy rates in frozen-thawed embryo transfer cycles and in patients with repeated implantation failure. The benefit is most consistently demonstrated in these specific subgroups rather than across all IVF patients indiscriminately. This is why careful patient selection is central to the Samarth IVF LAH programme
In indicated patients, some studies report benefit from LAH compared to unassisted transfer. Whether LAH is advised depends on your history; your doctor will explain if it applies to you. This represents a meaningful incremental gain, particularly for patients who have already experienced failed transfers.
LAH is a safe, well-established procedure when performed correctly by trained embryologists using calibrated laser equipment. The safety profile of modern laser hatching is excellent based on decades of clinical experience and extensive follow-up data on children born following LAH
Large follow-up studies of children born after LAH show no increase in congenital abnormalities, developmental problems, or childhood health issues compared to children born after standard IVF.
The infrared laser is directed at the zona pellucida only, not at the embryo cells. The thermal pulse is brief and precisely targeted. The embryo cells are not touched.
LAH has been in clinical use for over 30 years. The laser technology used today is far more precise and safe than early mechanical or chemical hatching methods.
LAH has been associated in some studies with a small increase in identical twinning rates (approximately 1 to 2 percent), possibly because the opening in the zona may allow the inner cell mass to split in rare cases. The absolute risk is very low.
| Factor | Natural Hatching | Laser Assisted Hatching |
|---|---|---|
| How zona is breached | Enzymatic and pressure-driven by embryo | Precise infrared laser pulse creates opening |
| Timing of hatching | Variable, depends on embryo | Facilitated by pre-made opening before transfer |
| Suitable for all embryos | Yes, standard process | Selective: indicated cases only |
| Benefit for frozen embryos | Zona may be harder after freeze-thaw | LAH overcomes post-thaw zona changes |
| Risk | Hatching failure if zona is too thick | Minimal: rare monozygotic twin risk |
For patients with repeated implantation failure (RIF), LAH is one component of a broader investigation and management plan. At Samarth IVF, RIF is investigated systematically before simply repeating a transfer with LAH. Other causes of implantation failure are assessed and addressed in parallel:
hysteroscopy to exclude polyps, adhesions, submucosal fibroids, or endometritis.
to identify a displaced window of implantation requiring personalised transfer timing.
high fragmentation can impair embryo development even when early-stage embryo quality appears normal.
selected investigations in specific clinical contexts.
PGT-A to screen for euploid embryos, and IMSI for ultra-high magnification sperm selection.
if Day 3 transfer was previously used, progressing to blastocyst culture. LAH applied to the blastocyst or cleavage-stage embryo.
LAH is available at Samarth IVF main centres equipped with diode laser micromanipulation systems integrated into the embryology laboratory. Our embryologists are trained in laser hatching protocols and perform LAH to consistent, quality-controlled standards.
Laser Assisted Hatching (LAH) is a precision laboratory technique where a controlled infrared laser beam creates a small opening in the zona pellucida (the outer shell of the embryo) immediately before embryo transfer. This assists the embryo in completing the hatching process required for implantation into the uterine lining. LAH is performed in the IVF laboratory by trained embryologists and takes approximately 2 to 5 minutes per embryo.
The embryo is enclosed within the zona pellucida from the moment of fertilisation. For implantation to occur, the blastocyst must completely escape from the zona pellucida, a process called hatching. Only after hatching can the trophectoderm cells of the blastocyst make direct contact with the endometrial lining and begin implantation. If the zona is too thick or fails to rupture at the right time, implantation cannot occur even if the embryo is otherwise healthy.
LAH is recommended for frozen-thawed embryos (FET cycles), embryos with thick zona pellucida, patients with repeated implantation failure after two or more good-quality embryo transfers, older patients above 37 to 38, patients with high FSH, slow-developing embryos, and embryos of borderline quality. LAH is not routinely recommended for all patients, particularly good-prognosis patients with fresh, naturally expanding blastocysts.
In the specific patient groups for which it is indicated, some studies report benefit from LAH compared to unassisted transfer. The benefit is most consistently demonstrated in frozen-thawed embryo transfer cycles, patients with thick zona pellucida, and those with repeated implantation failure. Evidence does not support LAH improving outcomes in unselected good-prognosis patients.
Yes. LAH is a well-established, safe procedure. The infrared laser is directed only at the zona pellucida, not at the embryo cells inside. The pulse is brief and precisely targeted to avoid any thermal damage to the embryo. Large follow-up studies of children born after LAH show no increase in birth defects, developmental problems, or childhood health issues compared to children born after standard IVF. There is a small possible increase in identical twinning of approximately 1 to 2 percent.
Laser Assisted Hatching is the modern, preferred form of assisted hatching. Earlier forms of assisted hatching used mechanical methods (a fine needle to pierce the zona) or chemical methods (acidified Tyrode solution to dissolve part of the zona). Laser hatching is now universally preferred as it is the most precise, reproducible, fastest, and safest method. At Samarth IVF, all assisted hatching is performed using calibrated diode laser systems.
LAH and ICSI are different procedures performed at different stages of the IVF process. ICSI (Intracytoplasmic Sperm Injection) is performed at the fertilisation stage, injecting a single sperm into each mature egg. LAH is performed on an already-developed embryo immediately before embryo transfer, creating an opening in the zona pellucida to assist hatching. Many IVF cycles include both ICSI (for fertilisation) and LAH (for the selected embryo at transfer), as they address different steps in the process.
No. LAH is performed entirely in the embryology laboratory on the embryo before it is loaded into the transfer catheter. The patient is not involved in or aware of the LAH procedure. The embryo transfer itself is the same comfortable, non-invasive outpatient procedure regardless of whether LAH has been performed.
Yes. For patients with repeated implantation failure, LAH is often used alongside other interventions including ERA (to personalise transfer timing), hysteroscopy (to exclude uterine cavity pathology), PGT-A (to screen embryos for chromosomal normality), IMSI (for sperm selection), and optimised stimulation protocols. A comprehensive approach addresses all possible contributing factors.
LAH is available at Samarth IVF main centres equipped with diode laser micromanipulation systems and trained embryology teams. Patients at all 14 Samarth IVF centres can be coordinated for embryo transfer with LAH at the nearest fully equipped main centre. Your treating doctor will advise whether LAH is recommended for your transfer and at which centre it will be performed.
Speak with our specialists — they will explain your options in plain language.
Wishing you and your family light, health and happiness this Diwali. — Samarth IVF
