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A birth defect is any abnormality that may be detected during pregnancy, at birth or in early childhood. These can range from minor to very severe conditions and can affect pregnancies and babies in a variety of ways.
With the decline of death (mortality) and illness (morbidity) in children from causes such as infection, birth defects are now more prominent as a serious health hazard of childhood. In Victoria approximately one in every 25 babies is affected by a birth defect.
The Victorian Perinatal Data Collection Unit (VPDCU) runs the Victorian Birth Defects Register (VBDR). The VBDR collects information on all infants born in Victoria since 1983 and determines how often birth defects occur.
Birth defects in Victoria
Around 127,000 babies were born in Victoria over the two years from 2003 to 2004. Of these, just over four per cent (around 2,700 babies each year) were born with a birth defect. In the case of a serious birth defect that can be detected during pregnancy, parents may choose to discontinue the pregnancy. So not all reported cases of birth defect represent live births.
The VBDR collects information on a range of factors that can influence the chance of having a baby with a birth defect. Some of these include:
- Gender of the child
- Number of foetuses (twins, triplets, quads)
- The mother’s age
- Other maternal factors, such as the mother’s country of birth and where she lives.
Top 10 birth defects in Victoria
With a few exceptions, the majority of birth defects most commonly found in Victoria are not severe or life threatening to the child. The incidence of the 10 most common conditions in Victoria in 2003–2004 (in order of prevalence) was found to be:
- Hypospadias – the urethral opening is located on the underside of the penis: one in 253 (male) births.
- Obstructive defects of the renal pelvis – abnormalities of the urinary tract: one in 253 births.
- Ventricular septal defect – a hole in the tissue that divides the two heart chambers: one in 309 births.
- Congenital dislocation of the hip – the ball of the thigh bone doesn’t fit snugly into the hip bone socket: one in 338 births.
- Trisomy 21 – also known as Down’s syndrome, caused by an additional 21st chromosome: one in 356 births.
- Hydrocephalus – a build-up of cerebrospinal fluid inside the skull: one in 980 births.
- Cleft palate – the roof of the mouth is split down the middle: one in 980 births.
- Trisomy 18 – also known as Edward syndrome, includes multiple abnormalities (including those of the heart, diaphragm, lung, kidneys, ureters and palate) caused by an additional 18th chromosome: one in 1,042 births.
- Renal agenesis and dysgenesis – one or both kidneys are missing (agenesis) or the kidney is malformed (dysgenesis): one in 1,389 births.
- Cleft lip and palate – the upper lip and roof of the mouth are split down the middle: one in 1,493 births.
Neural tube defects
Neural tube defects, such as anencephaly and spina bifida, occur just outside the top 10 most common birth defects but are widely known. Their prevalence has generally decreased since 1993, most likely due to an increased awareness by the public of their prevention and increased use of folic acid.
- Spina bifida – malformations of the spinal column: one in 1,639 births.
- Anencephaly – the brain is partially or completely absent: one in 1,587 births.
Maternal characteristics
Selected maternal characteristics associated with birth defects include:
- The prevalence of birth defects increases with the mother’s age. Five per cent (5.0%) of women 35–39 years of age and around seven per cent (7.4%) of women aged 40 years or more had a baby with a birth defect.
- Women aged 35 years and over account for 27 per cent of all mothers who have a pregnancy affected by a birth defect.
- Women from the Middle East are more likely to have babies with a birth defect than women from any of the other country of origin groups.
Infant characteristics
Selected infant characteristics associated with birth defects include:
- Birth defects were more commonly reported in males than females.
- Birth defects were recorded among 10.6 per cent of low birth weight infants (less than 2,500g) compared with 3.3 per cent of infants with birth weights of 2,500g or more.
- 9.8 per cent of premature infants (less than 37 weeks) had a birth defect compared to 3.3 per cent among term and post-term babies.
- 4.3 per cent of singleton births had a birth defect.
- 5 per cent of multiple births (twins, triplets, quads) had a birth defect.
- Within the multiple births, 50.1 per cent were the first born and 47.4 per cent were second born infants.
Perinatal mortality
Selected statistics reveal:
- Perinatal mortality is high among infants with birth defects.
A baby with a birth defect is 3.71 times more likely to die than a baby without a birth defect. (This figure excludes terminations of pregnancy for a birth defect both before and after 20 weeks gestation.)
Where to get help
Things to remember
- The Victorian Perinatal Data Collection Unit (VPDCU) runs the Victorian Birth Defects Register (VBDR).
- The VBDR collects information on all infants born in Victoria since 1983 and determines how often birth defects are occurring.
- The most common birth defects during this period include hypospadias, obstructive defects of the renal pelvis and ventricular septal defect.
You might also be interested in:
Birth defects - ambiguous genitalia.
Birth defects - central nervous system.
Birth defects - digestive tract.
Birth defects - drugs and medications.
Birth defects - heart abnormalities.
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