FAQs

Age affects our eggs more than any other factor. Generally, the younger we are, the better our egg count and egg quality

Your egg count is the number of follicles, or potential eggs, remaining in your ovaries. Though born with 1–2 million egg follicles, a woman loses upwards of 1,000 eggs per month until menopause, with the rate of loss increasing after 35. Low egg count can lead to infertility, and can also affect how successful a woman is with egg freezing or in vitro fertilization treatments.

Yes, egg count can be measured with two tests: an antral follicle count and an AMH
(anti-Müllerian hormone) test. These tests give an idea of not only your total egg count, but also of how many eggs you may be able to freeze during one cycle.

These tests are performed during our initial fertility assessment. Contact us to schedule an assessment.

Egg quality refers to whether an egg is genetically normal (euploid) or abnormal (aneuploid). As women age, the eggs inside their bodies are more prone to errors in their DNA. Abnormal eggs are not able to fertilize and develop properly, and can lead to infertility, miscarriage, or genetic disorders such as Down syndrome. Egg quality is the primary factor affecting fertility.

No, it’s not possible to measure the quality (or genetic normalcy) of an individual egg. But there’s a clear relationship between age and egg quality, so your age is a good proxy for how many normal eggs you may have.

A fertility assessment is a series of tests, including an AMH blood test and an antral follicle count, used to measure your egg count and assess other potential barriers to fertility. Together with your age and medical history, these tests give a doctor a clear picture of your fertility health and how successful egg freezing may be for you.

While your OB/GYN or at-home testing kits may be able to perform some of these tests, we strongly recommend doing this testing with an experienced fertility provider who will be best able to interpret the results. Contact us to schedule an assessment.

AMH is a protein hormone produced by cells inside the ovarian follicles. The level of AMH in the blood can help doctors estimate the number of follicles inside the ovaries (egg count). A typical AMH level for a fertile woman is 1.0–4.0 ng/ml.

An antral follicle count is performed by a doctor during an ultrasound. After visualizing the ovaries, the doctor can count the “activated” follicles in that cycle, and use that number to estimate her total egg count.

Egg freezing is the process of preserving some of your eggs by retrieving them from your ovaries, freezing them, and storing them so you can use them to get pregnant later on.

The short answer? To preserve your options. You might not be ready for babies right now (because of your relationships, health, career, finances, or any other reason), but know you want kids later. Or that you might want kids later. Or you really have no idea whatsoever, but you want to keep that option open. Freezing your eggs can give you more choices in the future.

Once eggs are removed from your body and frozen according to precise protocols in a specialized lab, they can no longer age. Your healthy, high quality eggs, once frozen, remain healthy and high quality, so you can use them to get pregnant later in life—when it might otherwise be hard to find healthy eggs.

Egg freezing typically entails 8–11 days of hormone injections to stimulate your ovaries to produce multiple eggs in one menstrual cycle, instead of the single egg they would typically produce. During this period, you’ll have 5–7 short “monitoring” visits where we’ll assess your progress and possibly make adjustments to your medication or schedule.

Finally, there’s a 15-minute surgical procedure performed under mild anesthesia to retrieve the eggs from your ovaries. This whole process, from the beginning of the injections through to the retrieval, is called a “cycle.” Learn more.

The egg freezing process begins with a fertility assessment and doctor consultation. Once you decide to freeze your eggs, you’ll have an appointment to ensure you know how to administer your medication and that you understand the process and your cycle schedule. How long these first few steps take is up to you—some women come in for an initial appointment and freeze their eggs with their next period, while some take more time to consider their plans and their options. Then, the egg freezing cycle itself takes about 14 days.

While you’re under sedation, the physician uses ultrasound guidance to insert a needle through
the vaginal wall into each ovary to draw out the eggs. The needle is attached to a catheter; the
eggs flow through the catheter into test tubes, which are then handed off to the embryologist, a
highly trained expert in the science of oocyte cryopreservation (that’s the technical name for egg
freezing). The entire procedure takes about 15 minutes. There are no scars left or stitches
required. Learn more.

Here at Extend Fertility, we use the Cryotec method of vitrification—it’s the cornerstone of our lab. Vitrification is a “flash freezing” method that cools cells so quickly to a temperature of -196º Celsius that they become “glass-like,” or “vitrified.”

Vitrification reduces the likelihood that the fluid in the egg will form ice crystals, which could damage it. The Cryotec method is an even more successful form of vitrification, consisting of a specific set of strict protocols for egg cryopreservation. These protocols increase the egg survival rate to over 90%.

Certain parts of it can be, depending on how sensitive you are. Injecting your medication is generally more of a pain than it is painful. The needles are very thin and you inject them into the fatty tissue around your belly. Some women feel bloated and crampy while taking this medication, because it has their ovaries working overtime. The transvaginal ultrasound exams used during egg freezing aren’t painful, but they can be a bit uncomfortable because, well, they’re transvaginal ultrasound exams.

During the egg retrieval, you’ll be under twilight anesthesia and won’t feel a thing. You may experience some pain when you wake up, like a little soreness in the vaginal area and/or some abdominal cramping, similar to how you might feel when you’re getting your period.

We recommend you take the day off from work on the day of your retrieval, so you can rest for the remainder of the day after the procedure. The vaginal soreness and cramping can last for a few days. But usually, that’s it.

A woman with a regular period can expect to get her next period at the same time she would have during a normal cycle, 28–30 days after her previous period began.

That depends on several factors, the most important one being age. That’s because your age at the time of freezing is the best way to predict how many of your eggs will be genetically normal. While there isn’t a specific “magic number” that will guarantee a pregnancy later on, women 34 or younger can feel confident that freezing 10 eggs will give them a high potential for creating at least one child if used later on. For women 35–38 years old, about 15 eggs is optimal; for women 38 and older, the data are more limited and less clear; a cautious approach would be to aim for freezing 20 eggs or more.

It depends. In general, when you are younger, you are more likely to freeze a higher number of eggs in one cycle. Younger women also produce a higher percentage of genetically healthy eggs, so they need to freeze fewer to begin with. Many younger women will reach their egg freezing target in just one attempt, while older women are likely to need to complete multiple egg freezing cycles to reach their goal. As part of your consultation with our doctors, we’ll let you know how many eggs we think you’ll be able to freeze in one cycle.

Yes, you can start a new cycle right after completing a prior cycle, so long as your baseline testing is normal. Some women choose to take a month or multiple months “off” between cycles for personal reasons, but it’s not required.

If you want to use your frozen eggs, they’ll be thawed and fertilized with partner or donor sperm using in vitro fertilization (IVF).

Your age at the time you freeze your eggs and how many eggs you freeze are the two most important factors affecting your chance of having a baby with frozen eggs. According to a recent study of over 500 cycles of in vitro fertilization in fertile women performed at Brigham & Women’s Hospital:

• If you’re under 35 and you freeze 10 eggs, your chances of at least one live birth using those eggs later are about 60–70%. If you freeze 20 eggs, you have about a 90% chance of those eggs resulting in at least one live birth later on.
• If you’re 37, your chances for at least one live birth later are about 50% with 10 frozen eggs and 75% with 20 frozen eggs.
• If you’re 40, your chances for at least one live birth later are about 30% with 10 frozen eggs and 50% with 20 frozen eggs.

It’s important to understand that there have been a limited number of studies looking at the success rate of using frozen eggs. This is because the use of vitrification for elective egg freezing is relatively new, and because when women freeze their eggs to preserve their fertility, they typically wait several years before using them. As a result, there are not yet many high-quality studies reporting large-scale results. However, the results of IVF and egg donor cycles give us a good foundation for understanding the potential for success with frozen eggs.

In general, any healthy woman who currently has at least some healthy eggs and is not yet ready to have a baby is a good candidate for egg freezing. As an initial step in the egg freezing process you’ll have a fertility assessment to gather information about your fertility and your overall health. Then, in a consultation, one of our physicians will review how effective egg freezing might be for you.

The younger you are, the more effective egg freezing will be for you. You’ll be able to freeze the highest number of healthy eggs before you turn 30, slightly fewer from 30–35, and then a much smaller yield over 35. The “sweet spot” for egg freezing is ages 27–34.

In your mid-to-late 30s or early 40s, you can at least partially compensate for low egg quality by freezing more eggs to increase your odds. This usually requires multiple egg freezing cycles, but it can give you a better chance of eventually achieving a healthy pregnancy.

Yes. Women with low AMH levels are still candidates for egg freezing, but they may need multiple egg freezing cycles to reach their goal.

No, not at Extend Fertility. Some clinics require women to use OCPs prior to their in vitro fertilization or egg freezing cycle because OCPs allow doctors, or the patients themselves, to manipulate the timing of their cycle for easier scheduling. However, studies have concluded that OCP use directly prior to a “stimulation” cycle (such as egg freezing) can result in a longer egg freezing cycle that requires more medication—and can lower the number of eggs that are eventually retrieved. So, we don’t prescribe birth control pills routinely as part of the egg freezing process.

Yes, you will need to stop taking hormonal birth control during the 8–14 days of your egg freezing cycle, but it can be resumed with the period following your egg retrieval. The medications used during your egg freezing cycle prompt your ovaries to produce multiple eggs during one menstrual cycle, instead of the one egg typically matured and ovulated. Hormonal birth control, on the other hand, is intended to prevent ovulation, so you wouldn’t want to take it during your egg freezing cycle.

No! Because IUDs don’t prevent pregnancy by preventing ovulation, they can stay in place throughout the egg freezing process. And because the egg retrieval is performed via a needle that goes through the wall of the vagina, there’s no chance of the IUD getting in the way.

Yes. While both processes use the same medications to prompt the ovaries to produce multiple eggs, the goal is different. During in vitro fertilization, eggs are fertilized in a lab to create embryos, either to transfer immediately as an infertility treatment or to freeze for later use. With egg freezing, you’re done after the egg retrieval—there’s no creation of an embryo, because the goal is simply to preserve your unfertilized eggs for the future.

Yes. When a woman freezes her eggs, she’s giving herself the option to get pregnant with her own eggs later in life. During egg donation, on the other hand, a young woman’s eggs are retrieved and either frozen or fertilized in order to be used for pregnancy by a different woman or couple. Here at Extend Fertility, we offer egg freezing, not egg donation.

Some women who freeze their eggs go on to find a partner and get pregnant the old-fashioned way. (For them, their banked eggs may give them a chance at having a second or third child, if they choose!) And some women decide not to use their eggs at all. In that case, they may be able to donate them to a specific person for reproductive purposes or have their eggs appropriately discarded.

You have the option to donate your unused eggs to someone you know, but you’ll need to decide if you want that option before you start your egg freezing cycle. That’s because egg donors must undergo a series of FDA and genetic tests, including infectious disease screening and a full physical, before they are cleared for donation. There is an additional cost associated with these tests. If you’d like the option to donate your eggs to someone you know in the future, talk to your fertility advisor, who can set up this testing for you. Extend Fertility does not currently offer the option of anonymous egg donation.

In vitro fertilization (IVF) is the process of combining sperm and egg in a laboratory to create embryos. IVF may be used as a treatment for infertility, to create embryos to freeze for later use, or as a way to use frozen eggs when you’re ready to get pregnant.

Intracytoplasmic sperm injection, or ICSI, is an IVF technique in which a single sperm is injected directly into the egg. ICSI is commonly used in the case of a male fertility issue that affects the sperm’s ability to naturally penetrate the egg, such as abnormal sperm morphology (size/shape) or motility (movement).

Preimplantation genetic screening (PGS) or preimplantation genetic diagnosis (PGD) are genetic tests performed on an embryo. PGS screens for extra or missing copies of chromosomes, such as those that cause miscarriage or Down syndrome. PGD looks for specific genetic disorders, such as cystic fibrosis.

If PGD/PGS is being used, embryologists will obtain a microscopic amount of material from the embryo in a procedure called “trophectoderm biopsy,” which will be sent to the genetics lab for analysis. Typically, all embryos biopsied will be frozen immediately to await the results of the PGD/PGS testing. Healthy embryos will then be selected for frozen embryo transfer.

IVF success rates depend on a few factors, including the age of the egg, the age of the sperm, the quality of the lab, how many eggs are retrieved, and the cause of infertility. Generally speaking, success rates for women under 35 are over 40% per cycle; for women 35–40, around 20–30% per cycle; and for women over 40, 15% or less per cycle.

In a “fresh” IVF cycle, an embryo is transferred into the uterus immediately after it’s reached the appropriate level of development (typically after 5–6 days). In a frozen or “freeze all” cycle, the embryos are frozen instead, and may later be thawed to use in an embryo transfer. Frozen cycles follow the same process as embryo freezing (below), but typically an embryo is thawed and transferred with the next menstrual cycle.

Doctors may recommend a frozen cycle to allow additional time for the uterine lining to grow for a higher chance of pregnancy, or pending the results of PGD/PGS testing.

Both are methods of fertility preservation that allow patients to use their healthy, young reproductive materials later on in life. During egg freezing, unfertilized eggs are frozen for use later. In embryo freezing, the eggs are fertilized to create embryos before they’re frozen.

Embryo freezing begins with hormone medication, injected over for 8–12 days, that stimulates the ovaries to produce multiple eggs. Once mature, the eggs are collected from the ovaries via an egg retrieval procedure. Sperm from a male partner or sperm donor is prepared through a process called “sperm washing,” which isolates healthy sperm to improve the chances of fertilization. The sperm is then combined with the egg in the laboratory (known as in vitro fertilization) to create embryos. The embryos develop for approximately 5 days under close monitoring by embryologists, and finally, they’re vitrified (flash frozen). Just as with eggs, once frozen, embryos remain as healthy and high quality as they were when they were created.

Embryo freezing is more appropriate for people in long-term relationships or marriages, who know they want to have children together one day. Egg freezing offers more options and simpler choices for patients that are single or not ready to create embryos with their partner.

Learn more about embryo freezing vs. egg freezing.

There was a time, using older slow freeze technology, when embryos survived the freezing and thawing process better than eggs, because embryos are slightly less delicate. However, the introduction of vitrification (flash freezing) has largely eliminated this difference. At Extend Fertility, the survival rates when freezing eggs vs. freezing embryos are very similar: 90% of eggs and 95% of embryos survive.

The hormone injections used in egg/embryo freezing and IVF aren’t carried by your regular neighborhood pharmacy counter. (Click here for a list of egg freezing medications.) We can recommend pharmacies that specialize in medications for egg freezing and other fertility treatments.

Medication isn’t part of our cycle price. Typically, they cost between $2,000 and $5,000. The healthcare team will help you estimate the amount of medication you’ll need for your cycle, so that you can calculate your overall medication cost.

Thankfully, side effects are uncommon, and those experiences are mostly minor. About 25% of women using stimulation medications experience headaches, mood swings, insomnia, hot or cold flashes, breast tenderness, bloating, or mild fluid retention. Additionally, because most of your medications will be given by injection, your injection site could become sore, red, or slightly bruised. Allergic reactions are very rare.

Occasionally, these medications can get the ovaries working too hard, resulting in what we call ovarian hyperstimulation syndrome (OHSS). OHSS is associated with swollen, enlarged ovaries and the collection of fluid in the abdominal cavity. In less than 5% of cases, OHSS can require monitoring or bedrest; in extreme cases (less than 1% of women taking these medications) OHSS can cause medical complications, like ovarian torsion, that might require surgery. The chances of OHSS are very small, but our healthcare team takes them seriously and takes all steps to prevent it.

Scientifically speaking, frozen eggs or embryos can be stored indefinitely. There have been numerous healthy babies born from eggs and embryos frozen for 5–10 years, with the longest reported successful thaw coming after 14 years for a frozen egg and 24 years for a frozen embryo. There is no evidence that the health or viability of frozen eggs or embryos decreases over time.

Your frozen eggs/embryos will be stored at New England Cryogenic Center (NECC) in Marlborough, MA, the industry leader in cryopreservation storage and shipping. The facility is in a secure business park and employs 24/7 security and monitoring.

Absolutely. In fact, it’s the safest and most secure environment possible for frozen tissue. NECC is registered and governed by the FDA, licensed with appropriate regulatory agencies, and is regularly inspected by several entities. NECC has provided cryostorage services for more than 25 years without a single failure.

The facility has video surveillance, an ADT alarm system, and motion detectors. All visitors must be identified and buzzed in. Each storage tank has its own separate monitor and multiple monitoring systems in place to ensure proper tank temperature and liquid nitrogen levels. Tanks are visually inspected daily. NECC is protected from power failures by backup generators, and they use a 9,000-gallon gravity-fed liquid nitrogen tank.

Your frozen eggs/embryos are transferred to NECC’s state-of-the-art cryogenic storage facility by NECC itself. We do not use a third-party transport company. NECC brings specialized travel tanks called “cryo-movers” to Extend Fertility, fills them, and then takes the filled tanks to their facility. This trip typically takes less than five hours, and the liquid nitrogen vapor in the shipping tanks can keep the eggs at the proper temperature for at least seven days.

There’s no evidence that moving your eggs or embryos from one lab to another affects their health or ability to become fertilized later. A review of over 1,200 donor egg cycle outcomes at Reproductive Biology Associates in Atlanta, Georgia, demonstrated that there’s no evidence of a decrease in survival rate, fertilization rate, blastocyst rate, implantation rate, or clinical pregnancy rate for shipped frozen eggs when compared to frozen eggs that have not been transported.

Absolutely. We provide a full range of fertility services for our patients who want to use their frozen eggs or embryos. But if you’ve relocated or you decide to pursue treatment with another clinic, we’ll help arrange for safe and expeditious transport of your frozen eggs/embryos and share all lab protocols and other necessary information necessary with your chosen provider or facility.

In New York, a fertility center can be accredited by either JCAHO, the Joint Commission on Accreditation of Healthcare Organizations, or by the American Association for Accreditation of Ambulatory Surgery Facilities (AAAASF). As the Joint Commission is focused on hospitals and AAAASF on ambulatory centers (which includes us), Extend Fertility Medical Practice chose AAAASF for accreditation.

AAAASF develops and implements standards of excellence to ensure the highest quality of patient care, establishing a means for measuring medical competence and providing an external source for evaluating patient safety in the ambulatory surgery setting.

Extend Fertility Medical Practice’s healthcare providers are Society for Assisted Reproductive Technologies (SART) members, and are fully trained, qualified, and certified. Our tissue bank director Sangita Jindal, PhD serves on the Executive Board for SART and for the Society for Reproductive Biologists and Technologists (SRBT), both affiliate societies within the American Society for Reproductive Medicine (ASRM).

We have successfully thawed and fertilized many eggs and embryos, and have successfully completed the transfers of many embryos created in our embryology lab, including embryos that have resulted from eggs we have frozen in our lab. The success rates and outcomes of these cases have met (and exceeded!) all accepted benchmarks for any high-performing IVF lab worldwide.

While there is no true consensus on an exact number, the “industry standard” for the percentage of eggs that fertilize normally is approximately 70%. Using both frozen and non-frozen oocytes (eggs), our lab’s fertilization rate to date is just under 80%.

The “industry standard” for embryo conversion rate (the percentage of fertilized eggs that become embryos) is at least 30–40%. The embryo conversion rate in our laboratory is approximately 60%.

Our laboratory was specially designed with state-of-the-art filters, air locks, and an air-handling system that uniquely isolates the lab environment from the rest of the floor. These precautions reduce the level of volatile organic compounds (VOCs), particulate, and microbial contaminant  to the lowest possible level to produce the safest possible environment for egg freezing. Our lab is designated a “Class 1000” laboratory, meaning that, on average, the air contains no more than 1,000 particles per every cubic foot. (For comparison, the typical office building contains anywhere from 500,000 to 1,000,000 particles per cubic foot of air.)

We use benchtop incubators instead of the older box incubator style that contains many patients’ eggs in one chamber. In the case of a box incubator, every time the incubator is opened to access a patient’s eggs, the environment inside changes—and because box incubators are larger, it takes longer for their interiors to return to the optimal temperature and pH. The six small chambers of the benchtop incubator each contain only one patient’s eggs, allowing precise control and stability of the incubator environment.

Our laboratory also features a custom design to ensure an optimal workflow and minimize distances when handling reproductive cells. Finally, we use temperature-controlled surfaces to maintain eggs at a normal body temperature of 37º Celsius throughout the lab.

We believe there is an opportunity to better serve more women who want to preserve their fertility by opening offices in other cities throughout the US. However, our efforts are currently focused on our New York City facility.

We currently see women from a number of different states—and even other countries—who travel to New York to freeze their eggs at our facility. Much of the pre-cycle testing and preparation can be completed remotely, but patients will need to be in New York City for about two weeks to complete the egg freezing cycle.

Some women diagnosed with cancer face an additional hurdle: the surgery, radiation, and chemotherapy used to treat their illness can also put their fertility at risk. Egg or embryo freezing preserves the option of genetic parenthood for when she’s healthy again.

Yes. We’ve created a program to make it easier and more affordable for women to preserve their fertility before cancer treatment, including a $700 discount, a healthcare team with expertise in oncofertility, expedited scheduling, and partnerships with organizations that support women with cancer diagnoses. Learn more.

There’s no evidence of a connection between BRCA gene mutations and an increased risk of infertility, but women who test positive for the BRCA1 and 2 mutations (and therefore have a higher chance of cancer) also have a higher chance of losing their fertility as a result of cancer treatment. Additionally, women who choose to remove their ovaries and fallopian tubes as a preventative measure—lowering their chances of breast cancer and nearly eliminating their chances of ovarian cancer—also eliminate the possibility of getting pregnant naturally.

That’s why many experts are now recommending that women who test positive for one of the BRCA mutations explore their options for fertility preservation. Learn more about BRCA mutations and fertility.

Endometriosis is a chronic, benign (non-cancerous) inflammatory disease, defined by the existence of “ectopic” (misplaced) endometrial (uterine lining) tissue. In other words, uterine lining cells that exist outside the uterus, such as in areas of the pelvis near the uterus, the vagina, cervix, intestines, bladder, or, rarely, in more remote areas of the body. These tissues grow, thicken, breakdown, and bleed just like the endometrium inside the uterus, except because they’re outside, this cycle can cause irritation or inflammation in surrounding organs or even produce scar tissue, known as “adhesions,” that can cause organs to attach to each other.

Symptoms of endometriosis include very painful periods, pain with sex, and reduced fertility. Endometriosis is common; experts estimate is affects at least 10% of reproductive-age women.

There is no cure for endometriosis, but there are multiple options available to manage symptoms, including medical and hormonal therapies (such as hormonal birth control) as well as surgeries to remove misplaced endometrial tissue. Endometriosis is an active area of research, with multiple new drugs currently in clinical trials to improve treatment options.

Endometriosis creates scar tissue in the reproductive system that can impede fertility, and may also decrease egg quality as it creates an inflammatory environment in the reproductive system. Additionally, many treatments that alleviate the symptoms of endometriosis, such as surgery, can affect the ovaries and reduce ovarian reserve (the number of eggs remaining in the ovary). Experts estimate that approximately 40% of unexplained infertility may be due to endometriosis, and studies demonstrate that women with even mild cases of endometriosis have only a 2–4% chance of getting pregnant each month (compared to the 15–20% chance healthy women have).

Because endometriosis puts women at risk for infertility and/or ovarian damage, women with endometriosis who aren’t yet ready to get pregnant are excellent candidates for fertility preservation.

A uterine fibroid is a benign (non-cancerous) tumor (overgrowth of cells). They are very common, and for most women no big deal.

For some women—though it’s uncommon— fibroids can make it difficult to get or stay pregnant. Fibroids don’t interfere with ovulation, but if they are especially large or there are multiple fibroids, they can prevent the uterus from doing what it’s supposed to do to support conception and pregnancy.

Because most women with fibroids don’t experience any symptoms, the most common treatment is no treatment at all—just “watchful waiting.” But for women with significant symptoms, treatment or removal by a variety of surgical methods might be deemed necessary for their health, comfort, and quality of life. It’s important to remember that surgical treatment for fibroids may affect fertility more than the fibroids themselves.

Freezing eggs before some fibroid treatments, such as embolization, prevents those eggs from being damaged inadvertently. And freezing eggs/embryos also offers women who are unable to get or stay pregnant on their own—because of fibroids or surgery—the chance to have a baby with a surrogate.

No—hormonal birth control doesn’t have a long-term effect on fertility. Within a few months of stopping birth control, the medication fully metabolizes and clears out of the system (the only exception to this is the birth control shot, which is intended to be a longer-acting form of birth control and might take longer to “wear off”). Women who previously used hormonal birth control get pregnant at the same rates as other women their age.

The hormone in emergency contraception such as Plan B—a high dose of a progestin (levonorgestrel)—is metabolized relatively quickly and has not been shown to have any long-term impact on health, even when taken multiple times. Use of emergency contraception will not affect your chances of getting pregnant later. Because emergency contraception is not 100% effective, it’s better for women who want to avoid pregnancy to use a reliable form of proactive contraception, such as an IUD (intrauterine device).