As discussed in our previous article dedicated to birth defects, preventing them first requires an understanding of how they develop and the factors influencing their occurrence. One great example of this relates to the discovery of the association between folate deficiencies and neural tube defects (NTDs). Upon this discovery, folic acid fortified flour was introduced in Canada and there were efforts to increase public awareness about the importance of folic acid supplementation during pregnancy. These efforts led to a significant reduction in the rates of NTDs between 1997 and 1998. Although public awareness about the consequences of folate deficiency was largely successful in reducing the rates of NTDs, this is not always the case since it is usually much more difficult to change human behaviour. The harmful effects of alcohol consumption on developing fetuses have been known for over 45 years and yet each year in Canada an estimated 3,000 babies are born with Fetal Alcohol Spectrum Disorder, a completely preventable disease. Although it is unlikely that we will ever be able to prevent birth defects entirely, research tells us that there are still many ways in which we can reduce the risk of our children having a birth defect.

Ways to reduce risk for birth defects

• See your doctor for a preconception checkup: Make sure you are in good health before you try and get pregnant. Getting a preconception checkup helps to ensure a healthy pregnancy for both you and your baby.

• Get treatment for any medical conditions you may have: Untreated medical conditions such as diabetes, hypertension, and thyroid disease increase likelihood of your baby having a birth defect.

• Do what you can to prevent infections: Not all infections can be prevented, but there are ways you can reduce the chances of developing infections and therefore reduce the chances of your baby having a birth defect. For example, make sure your vaccinations are up to date, avoid travel to areas where Zika virus is spreading, and limit your exposure to toxoplasmosis by not eating raw/undercooked meat or unwashed vegetables and having someone else clean your cats litter box.

• Get to a healthy weight before getting pregnant: Obesity increases the risk of having a child with a birth defect. Being active every day and eating healthy foods like fruit and vegetables while cutting out processed foods can help reduce this risk. Talk to your doctor if you need help losing weight.

• Ensure you are getting proper nutrition: Proper nutrition is important for your baby’s development and for an overall healthy pregnancy, and deficiencies in key nutrients like folate have been linked to specific birth defects. Do your best to have a well-balanced diet and consider taking prenatal multivitamin supplements, which have been shown to reduce the risk for a number of different birth defects.

• Talk to your doctor about any medications you take: The effects of many medications on fetal development are still unknown, therefore the safest option is to take the fewest medications possible. Sometimes prescribed medications may be critical for your own health, even if they might be harmful to your baby. Talk to your doctor to see if there is a safer alternative for any medications you are taking, and make sure talk to your doctor before starting or stopping taking any medications.

• Don’t smoke, drink alcohol, use marijuana or any other recreational drugs: These substances are known to increase the risk of birth defects. Talk to your doctor if you need help quitting.

• Avoid harmful substances in your environment: For example, talk to your boss about making modifications to your job if you’re exposed to harmful substances at work.

Learn about your genes with genetic counselling

If certain health conditions are common in your family, if prenatal screens indicate an increased risk for your current pregnancy, or if you have a child/previous pregnancy affected by a birth defect then you should think about seeing a genetic counsellor. A genetic counsellor can help you understand how your genetics influence the chances of your baby having a birth defect, how these health conditions are passed on in families and the impact they will have on you and your baby’s health. Additionally, they can also help explain test results, so you are able to make more informed decisions surrounding your pregnancy and your baby’s healthcare. If your genetics increase the risk of your child having a birth defect, a genetic counsellor will talk to you about ways you can manage these risks. See our previous blog post if you would like more info about genetic counselling.

Prenatal diagnosis and pregnancy termination

One of the ways in which birth defects are prevented is through pregnancy termination following a prenatal diagnosis. It is important to note that prenatal diagnosis, ultrasound monitoring, and early intervention can go a long way in reducing morbidity for babies born with some birth defects. This article is not advocating for the termination of pregnancies diagnosed with birth defects, but rather exploring the impact prenatal diagnosis and pregnancy termination have had on the prevalence of birth defects. If you are concerned about a birth defect in your pregnancy and you are unsure about your options, consider seeing a genetic counsellor.

The most recent Canadian report on birth defects and related mortality tells us that in recent decades, the rates of fetal death in early pregnancy have been increasing while the rates of fetal death late in pregnancy are decreasing. Infant deaths associated with birth defects have also been declining during this time. These trends reflect the increased ability of tests to detect birth defects early in pregnancy and pregnancy terminations that sometimes follow a diagnosis. Improvements made in the management of congenital heart defects over the last few decades also likely influence the decline in infant deaths related to birth defects, seeing as congenital heart defects are a major cause of infant mortality; however, these improvements do not account for the changing trends seen in birth defect related fetal death.

It makes sense that the increased sensitivity and widespread uptake of prenatal screening and diagnosis will affect the prevalence of birth defects differently. After all, birth defects vary considerably in their severity as well as the availability of treatments. Some birth defects are also easier to detect during pregnancy, and it makes sense that prenatal diagnosis will have a greater impact on the birth prevalence of these defects. See our previous blog post if you’d like more info on prenatal screening and diagnosis.

Adapted from Congenital Anomalies in Canada 2013: A Perinatal Health Surveillance Report

Down syndrome is one of conditions that are now able to be reliably detected during pregnancy. Screening tests for Down syndrome have significantly increased in sensitivity and are able to detect the condition in about 90-99% of affected pregnancies, depending on the test. However, screening tests are generally focused on identifying as many affected pregnancies as possible. In the case of Down syndrome, these screening tests have a false positive rate of 2-5%. This means that 2-5% of the pregnancies screening tests detected Down syndrome in will not actually be affected by the condition. If desired, invasive prenatal tests are available to confirm this diagnosis. These invasive diagnostic tests themselves can pose a risk to developing embryos, and therefore they are usually reserved for cases where a defect is already suspected. Approximately 1 in 4 pregnancies will be terminated following a prenatal diagnosis of Down syndrome. Since advanced maternal age is considered a risk factor for Down syndrome, we would expect that the rates of Down syndrome would be increasing as more and more women are deciding to wait to have children. What we are seeing however, is that the national birth prevalence rates are remaining relatively stable, reflective of the increased access to and advances in the ability of tests to screen for and diagnose Down syndrome prenatally.

Detection rates for neural tube defects are quite high using a combination of maternal serum screening tests and ultrasounds to visually confirm a diagnosis. Virtually all cases of anencephaly can be detected in pregnancy by prenatal ultrasounds. Considering that babies with this birth defect do not survive, early detection may be able to ease the emotional toll on parents. About 95% of cases of spina bifida, another neural tube defect, are also able to be detected during pregnancy. It appears that the ability for neural tube defects to be diagnosed prenatally has been a factor in the prevention of these birth defects. One study in British Columbia found the diagnosis of a neural tube defect was followed by pregnancy termination in 72.6% of cases.

It’s not quite clear if improvements in prenatal diagnosis for congenital heart defects have led to a decrease in the birth prevalence of these conditions. Heart defects are diagnosed prenatally using ultrasounds and fetal echocardiograms. Out of all cases of congenital heart defects, 1 in 3 are diagnosed prenatally, and this number increases to 60-80% for severe heart defects. Rates of pregnancy termination after diagnosis can range from 30% to 60%, this variation existing because pregnancy termination rates increase for heart defects that are associated with additional birth defects. Prenatal diagnosis is credited as having decreased the birth prevalence of congenital heart defects by about 21%, although recent improvement in the treatment of heart defects means that more parents are choosing surgical correction of the defect after birth instead of pregnancy termination.

Compared to some other birth defects, the effect of prenatal diagnosis on the birth prevalence of orofacial clefts has been minimal. Compared to the only 0.3% of cleft palates diagnosed in pregnancy, cleft lips are significantly more likely to be detected. Detection rates for cleft lips range from 20.3% when alone to 33.3% when associated with an additional clef of the primary palate. Orofacial clefts are more likely to be detected when they are associated with other birth defects and likewise, pregnancy terminations are more common when additional defects are present. Overall, cases that result in terminated pregnancies make up less than 5% of the total cases of orofacial clefts.

While major limb deficiency defects, like a missing arm or leg, can be easily diagnosed by ultrasound in the second trimester, smaller defects can be much more difficult to detect. Overall, detection rates for limb deficiency defects range from as low as 20% to as high as 64%. In addition to the type and severity of limb deficiency, rates of detection are affected by the presence of other defects and ultrasound screening protocols. The prevalence of limb deficiency defects has been decreasing and while prenatal diagnosis and pregnancy termination may be a factor, it’s likely that decreases in the rates of cigarette smoking and other risk factors are also contributing.

Gastroschisis is another birth defect that is able to be reliably diagnosed in pregnancy. Maternal serum screening tests in combination with ultrasounds are able to prenatally diagnose 94% of gastroschisis cases. However, pregnancy termination is rare when gastroschisis is present as an isolated defect, and additional defects are only present in less than 10% of cases. Overall, prenatal diagnosis has not had much effect on the birth prevalence rates for gastroschisis.

Although advances in prenatal screening and diagnostic tests in the last decade have made a significant impact on the prevalence of Down syndrome and neural tube defects, still only 1-3% of major birth defects are diagnosed prenatally. This emphasizes the importance of primary prevention in efforts to reduce the impact of birth defects.

Adapted from Congenital Anomalies in Canada 2013: A Perinatal Health Surveillance Report

The social perspective in birth defect prevention

Birth defects continue to be a major challenge in Canadian health care, affecting 3-5% of newborns, and the impact of these birth defects on the levels of infant mortality and childhood morbidity are profound. A majority of birth defects are the result of an interaction between genetic predisposition and environmental exposures, and even though most defects are not preventable, understanding more about risk factors is key step towards reducing the amount of suffering associated with these health conditions. Folic acid food fortification and rubella vaccination programs are great examples of how successful primary prevention strategies can be. Unfortunately, more work needs to be done to reduce the impact of other risk factors. Individuals and families of lower socioeconomic status are disproportionately affected by birth defects. They are also the ones who will be more severely impacted by financial and employment challenges, while also having the least access to support for depression or other mental health issues associated with lifelong morbidity, social exclusion, and self-esteem issues. There is also an issue of accessibility with regards to prenatal screening and diagnosis, as these tests are not cheap without insurance. Of the risk factors discussed in this article, most of them disproportionately affect lower socioeconomic classes. Reducing socioeconomic inequalities should therefore be a particular point of interest for those interested in reducing the impact of birth defects.

This article has been produced by Jenna Phillips, B.Sc. Reproduction and reuse of any portion of this content requires Merogenomics Inc. permission and source acknowledgment. It is your responsibility to obtain additional permissions from the third party owners that might be cited by Merogenomics Inc. Merogenomics Inc. disclaims any responsibility for any use you make of content owned by third parties without their permission.

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