How does NuvaRing work?


NuvaRing Contraception »

Artificial female reproductive hormones that affect ovulation are located inside the NuvaRing core during the manufacturing process. Once NuvaRing is inside the vagina, these hormones are absorbed through the plastic and so released from the ring to the local areas of your female reproductive system and also into your blood stream. The presence of these hormones prevents the release of your ova and therefore ovulation.

Your female ovaries are a store of ova that when fertilised by male sperm results with fertilisation of the ova and pregnancy. The release of the ova from the store within the ovary is timed to occur every few weeks. When an ova is released from the store it is called ovulation. Ovulation occurs at around 11-14 days after a period (or menstruation). Menstruation is when a small amount of bleeding occurs from your womb (or uterus). This bleeding passes through the vagina to the external surfaces of your reproductive system.

Ovulation is controlled by hormones that are released from the ovary and other organs such as your pituitary gland. The major hormones controlling the function of the female reproductive systems are progesterone and oestrogen. However these hormones function by controlling other hormones, together forming the sequence of events leading to ovulation, this occurs as a cycle of events. The events are the raising and lowering of hormone levels that in turn stimulate the raising and lowering of the next hormones in the sequence or cycle, including oestrogen or  progesterone. This sequence of events is called a cycle because it occurs over approximately 1 month (4 weeks) and the same sequence is repeated every month or 4 weeks on average. This is because within each cycle the events (changes in hormone levels) leading to completion of the cycle also stimulate the re starting off of a new cycle from the beginning!

Your oestrogen levels are highest and peak during ovulation, after ovulation progesterone levels increase and are high to prevent further ovulations. After ovulation a fertilised ova may implant into the endometrium (the lining of the womb) and then continue to grow inside your womb (uterus) after implantation. The high progesterone and prevention of ovulation immediately after the previous ovulation and during implantation is a way of naturally preventing (i) wastage of ova, if an ova has already been fertilised another is not needed and (ii) multiple fertilisations such as twins, triplets or more embryos developing.

The female body can comfortably maintain one fertilisation and the growth of that embryo to a foetus, to create a baby and may even support twins or triplets. However, for the pregnancy to be viable and all offspring to survive, ideally only one ovum (egg) is released from your ovary and fertilised. During pregnancy the progesterone levels remain high and also maintain the endometrium in an ideal condition for a pregnancy. If an ovum isn’t fertilised, some of your endometrium is shed and this is termed menstruation (or your period). This stage of and during menstruation is associated with falling, low levels of oestrogen and progesterone, bleeding and no pregnancy.

How does the release of hormones within NuvaRing prevent pregnancy?

All hormonal contraceptives prevent pregnancy by changing the normal hormonal levels, thus preventing or decreasing how often ovulation occurs. NuvaRing stabilises oestrogen at relatively high levels (not peak levels), this subsequently prevents ovulation that requires peak levels and changes the levels of other hormones involved in ovulation, that respond to raised oestrogen levels. Having higher, stable oestrogen levels makes your body behave as it does after an ovulation, yet ovulation doesn’t actually occur! This then prevents further ovulation and the oestrogen levels also helps to prevent unpredictable bleeding times or small amounts of random bleeding (spotting).

The relatively high and stable progesterone levels released from NuvaRing also prevents further ovulation, whilst combined with raised oestrogen prevents menstruation (menstruation requires low oestrogen and progesterone). These constant raised levels of oestrogen and progesterone prevent the initiation of a new cycle and further ovulations. The menstruation cycle is essentially stopped or maintained at the stage of post ovulation (after ovulation) which normally occurs just before menstruation or just before a fertilised ovum would be implanted. This is why on removal of NuvaRing (and therefore the artificial supply of additional hormones) on the 4th week after insertion, menstruation occurs. The cycle is released from being in essence paused just before a period, combined with the drop in the oestrogen and progesterone levels that naturally stimulate menstruation.

The NuvaRing also has other effects on the female reproductive system. The addition of the artificial hormones also changes the thickness (or viscosity) of naturally occurring mucus around the opening of your vagina into the uterus. This area is termed the cervix. This change of mucus levels impedes the progress of the sperm through the cervix into the uterus and near the ovaries and ova. The progesterone may also inhibit the movement of sperm. Therefore even if eggs are released, the male sperm are physically prevented from coming into contact with the ova and cannot therefore fertilise the ova and cause pregnancy.

The NuvaRing also stimulates changes in the endometrium (the lining of the womb). The level of oestrogen available alters the secretions from the endometrium and the level of progesterone inhibits the glands within the endometrium that produce the secretions. This may prevent the endometrium from supporting a fertilised ova and hence a growing embryo. Therefore in the unlikely event of an ovum being released from the ovary and sperm physically coming into contact to fertilise the ova, the implantation of a fertilised ova would be adversely affected and make pregnancy less likely.

The use of hormones to prevent unwanted pregnancies has been around since the 1960’s, however the concentrations of hormones used in oral contraceptives then, were 5-10 times higher than they are now. These new lower doses are considered much safer than those used when oral contraceptives were first introduced for use in the 1960’s.

The hormones traditionally used are the naturally occurring hormones, progesterone and estrogen which drive the female cycle. The estrogen and progesterone used to formulate the oral contraceptives have in the past been derived from animals, such as by extraction from the urine of pregnant horse’s. More recently synthetic hormones, that are copies of the naturally occurring human hormones, have been made within test tubes of the laboratory from small chemical molecules. Some contraceptives may contain semi-synthetic hormones, those that are naturally derived for instance from animals and then later modified chemically within the laboratory. These synthetic or semi-synthetic hormones have new chemical names and may have more potent or efficient effects on the female reproductive system than naturally derived animal hormones.

What are the hormones within NuvaRing?

Daily the NuvaRing releases the hormones EthinylEstradiol (EE) at 15 μg (15 millionth of a gram) and etonogestrel at 120 μg (120 millionth of a gram). Oral contraceptives may have higher concentrations of EE at 20-50 µg compared with the 15 µg EE that is within NuvaRing. EE at 15 µg is the lowest dosage in use for contraceptives. These hormones within NuvaRing inhibit ovulation by increasing the action of oestrogen and progesterone. These hormones in turn control other hormones occurring within your monthly cycle such as follicle stimulating hormone (FSH) and Luteinising hormone (LH).

What is Ethinylestradiol (EE) that is released from the NuvaRing?

Ethinylestradiol (EE) is a form of oestrogen. It is an an alkylated Estradiol. Estradiol is a naturally occurring form of osestrogen that is then modified in the laboratory to form EE. For females, Estradiol stimulates the growth of the female reproductive system and levels also affect where fat is deposited around the body.

Women who haven’t gone through the menopause would have around 30 pg/mL of oestrogen within their blood normally, (that is 30 trillionth of a gram per millilitre of blood) and this peaks to around 400 pg/mL  during ovulation, falling back down again for the reminder of the cycle and menstruation to around 25-30 pg/mL.

EE is also used in combination with other hormones or synthetic hormones to control unwanted hair growth or loss and dermatological disorders such as acne vulgaris, hirsutism (excessive hair growth on the face and body), seborrhea dermatitis (flaky dry skin caused by inflammation) and female pattern hair loss (FPHL). EE in combination with other drugs is also used as a treatment for osteoporosis and to gain relief from some menopausal symptoms, such as vaginal atrophy.

What is etonogestrel that is released from NuvaRing?

Etonogestrel (ENG) is a synthetic form of progesterone (the naturally occurring hormone). It is also used in oral contraceptives and the implantation device (Implanon or Nexplanon®) that is fitted under the skin lasting for several months, giving slow release of the hormones into the blood system. The normal levels of progesterone within the blood for females varies depending on the timing of the cycle, however when ovulation isn’t occurring the levels are less than 1 ng/mL (less than 1000pg/mL) and increase to reach levels from  5 to 20 ng/mL (5000-20,000pg/mL)) during ovulation. This form of progesterone added to the ring may reduce the risk of developing blood clots (venous thromboembolism (VTE)).

How much of the hormones are released from NuvaRing into our bloodstream?

The levels of the hormones detected within your blood when you have NuvaRing inserted are at levels comparable to those found in the blood of women using the implantation device. The release of hormones occurs by slow release from NuvaRing, similarly to the technology that allows the slow release of hormones from the implantation devices as mentioned earlier. The hormones are absorbed through the vaginal lining directly into your bloodstream. However during the initial insertion hormone levels in your blood do increase and then over the following three weeks of NuvaRing insertion, levels become stable. The average levels over the 3 weeks for EE (EthinylEstradiol the oestrogen) are at 18.3 pg/mL and for ENG (Etonogestrel the progesterone) 1476pg/mL (or 1.476 ng/mL).


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