Labial fusion, or labial adhesion, is when the small inner lips around the entrance to the vagina become sealed together and covered with a fleshy membrane.
It is sometimes seen in babies and young girls and is usually nothing to worry about.
The membrane usually completely seals the vaginal opening, leaving a very small gap at the front that urine passes through.
For most babies or girls, labial fusion does not cause any problems and is often discovered accidentally by a parent or carer during nappy changing or bathing.
Your GP can confirm labial fusion after doing a routine examination of the child's genital area.
Who is affected?
Labial fusion is fairly common, affecting around 2% of babies and young girls aged between three months and six years. It is most common in girls between the ages of one and two.
The problem is rarely seen in girls after they begin puberty, because this is when they start to produce the hormone oestrogen. Oestrogen makes adhesions of the labia less likely to occur.
Why it happens
There are two parts of the labia – the outer labia are larger and fatter, while the inner labia are folds of skin between the outer labia.
It is not certain what causes labial fusion, but it usually occurs as a result of some irritation or inflammation (swelling) of the vaginal area, known as vaginitis.
This can cause the inner lips of the vulva to become sticky and, without enough oestrogen in the body, the lips can stay stuck together and gradually become firmly joined.
How it is treated
Treatment for labial fusion is not recommended unless there are other symptoms, such as dribbling after urination, which may cause problems or discomfort.
Treatment is with oestrogen cream or ointment applied daily or, rarely, surgical separation.
A small blob of the cream or ointment is applied daily on to the central line of the membrane covering the vagina.
This should be continued for four to six weeks until the membrane starts to dissolve and the labia eventually separate completely. When the membrane dissolves, you should stop applying the cream.
To enable the labial edges to heal properly and prevent another labial fusion forming, you should continue to apply an emollient cream, such as a nappy rash cream, for a few months after the fusion has separated.
Oestrogen creams and ointments can occasionally cause side effects, especially if used for periods longer than a few weeks. They should not be used for longer than six weeks. Side effects can include:
irritation around the genital area
temporary pigmentation (darkening) of the skin in the genital area
vaginal spotting or bleeding after you stop using the cream or ointment
Side effects should go away after you stop using the oestrogen cream or ointment.
Surgery is very rarely needed to treat labial fusion. It may be considered if:
an oestrogen cream or ointment does not work
a fusion is particularly thick and severe
there is trapped urine in the vagina, which can dribble out after urination and cause vulval soreness
Labial fusions are relatively easy to separate – they can usually be gently pulled apart by hand, or a small blunt probe is used.
A surgical separation is usually performed under a general or local anaesthetic, as the procedure can be quite painful and can cause distress (a general anaesthetic means you are put to sleep; a local anaesthetic means numbing the area).
To allow the labial edges to heal properly and prevent another labial fusion forming, you will be advised to apply an emollient cream, such as a nappy rash cream or Vaseline, to the labia for a few weeks afterwards.
There is a high chance the fusion will return after treatment, whether this is with oestrogen cream or surgery.
A labial fusion or adhesion usually separates naturally without treatment. Eventually, when the child goes through puberty, the production of the hormone oestrogen causes the labia to separate.
In most cases, a fusion corrects itself during puberty. In up to 14% of cases, a fusion may recur, but this tendency usually stops before puberty begins.
Labial fusion is not linked to any medical condition and has no long-term implications for your child – it will not affect her future fertility or sexual life.
Rarely, labial fusion can cause:
infection (such as a urinary tract infection)
soreness or pain in the genital area
urine becoming trapped in the vagina, leading to leaking of urine between visits to the toilet