BI215-A: Principles of Genetics

Women who get pregnant after 35 are at increased risk of gestational diabetes, high blood pressure, miscarriage, birth defects, and difficult labor ("Risks of Pregnancy Over Age 30.") However, this is obviously not all due to pregnancy, and there are still many healthy women over 35 who, while they may be at increased risk of a child with genetic abnormalities due to advancing age, do not have other health problems that would complicate pregnancy. In other words, we may be using age as a proxy for poor health. It's also important to note that while the odds of having pregnancy complications is higher in older women compared with younger, the percentage of women who actually do experience these complications remains low (Schummers, Laura et al.). For example, in a 2004-2014 cohort study, Schummers et al. found that neonatal mortality rate rose from about 0.25% to 0.75%. The rate tripled, but the absolute risk is still very low. 

The risk of down syndrome, also known as trisomy 21 (a condition in which a child is born with an extra chromosome), increases as a mother ages. The risk is about 0.0004% for mothers at age 25, and 1% for mothers at age 40, although most babies with Down syndrome are born to mothers under 35 because women under 35 are more likely to have children ("Pregnancy Over Age 30."). Screening for Down syndrome is available and is used: there is both non-specific screening and diagnostic screening, usually chorionic villus sampling or amniocentesis ("Down Syndrome"). However, there are ethical concerns with screening, particularly because individuals with trisomy 21 can and do live long and meaningful lives. In spite of that, almost all babies conceived with Down syndrome are aborted in Iceland, and 67% of babies conceived with Down syndrome are aborted in the U.S. (Quinones & Lajka).

Another condition that increases with maternal age is trisomy 13 ("Trisomy 13 Syndrome"). Children with trisomy 13 are at increased risk of weak muscle tone, heart and spine defects, physical abnormalities such as extra fingers, mental retardation ("Trisomy 13").  This is a rare condition, affecting only about 1 in 16,000 newborns ("Trisomy 13"). There is no treatment for trisomy 13, but there is treatment available for secondary health issues, as well as genetic screening ("Trisomy 13").

Triple x syndrome is another genetic condition in which a female is born with an extra x chromosome ("Triple X Syndrome"). Although girls with this condition may be exceedingly tall, have mental or physical retardation, and in approximately 10% of children, have kidney dysfunction or seizures, most are healthy and able to live normal lives ("Triple X Syndrome"). There is no treatment for triple x syndrome as a condition, but there is treatment for secondary health conditions associated with it, as well as genetic screening ("Triple X Syndrome").

Would I consider pregnancy after 35? Absolutely! I was a post 35 baby, and the only lasting effect on me was having parents with a few extra years of experience. The actual risk of complications is still quite low, especially for mothers who are in good health before the pregnancy (Schummers, Laura et al.). Besides, at no time is a woman guaranteed a healthy pregnancy or a healthy baby. Babies who are born with genetic defects are not less valuable, nor are their lives less meaningful. The condition with the highest risk for post 35 mothers is Down syndrome, which again, is not a death sentence, nor does it deprive people of meaningful lives. If we eliminate children with Down syndrome before they're born, or refuse to have babies before 35 out of fear, we say to people with Down syndrome, "Better to never have been born than to be born with Downs." As a future pediatric infectious disease physician, I will treat a lot of sick children--kids with immunocompromised fever due to chemotherapy, babies with HIV infection acquired from their moms, children who are immunosuppressed so their bodies won't reject a transplant. These children may not live normal lives, but that does not make their lives less meaningful.

Even babies born with such serious conditions as trisomy 13 are not lost causes. Medicine is improving, giving us more resources to help these children. Neonatology has been steadily advancing: "a 1-kg infant who was born in 1960 had a mortality risk of 95% but had a 95% probability of survival by 2000" (Philip, A.). These advances came because we fought, because we pushed the bounds, because we refused to accept that this or that condition was a death sentence. 

That said, it is an interesting and somewhat concerning finding that maternal age is increasing. It should be noted that while the mean maternal age is increasing, this is partially due to the decline in teenage pregnancy, which is probably a good thing (Ferré C, Callaghan W, Olson C, Sharma A, Barfield W). However, many women are choosing to put off pregnancy to get an education or move forward in their career. While I'm absolutely for women getting an education or having a career, I do wonder if women put off having children not because they really want to but because the environment they're working in is so hostile to it. Many businesses see employees with children as less dedicated, and may not accommodate mothers (or fathers). There may be no paid family leave, few daycare options, inflexible scheduling, no place to pump breast milk, pressure from supervisors, and no other parents. Furthermore, while women are encouraged to do almost any job in the workforce, from being a teacher to being a nuclear engineer, they are rarely encouraged to be mothers. Be almost anything but a stay-at-home mom as a woman, and your choices will be celebrated. Women who chose to stay home, however, are sometimes seen to have wasted their potential. Though we make space for women to succeed in what were traditionally men's careers, we do not always allow them to succeed as women, insisting that they conform to traditionally male roles and characteristics. We value money and status and prestige, and not the immense impact that a mother and a father can have on a child. Therefore, women will often choose to first have money and status and prestige, and then have a child.

Allen, Emily Graves et al. “Maternal age and risk for trisomy 21 assessed by the origin of chromosome nondisjunction: a report from the Atlanta and National Down Syndrome Projects.” Human genetics vol. 125,1 (2009): 41-52. doi:10.1007/s00439-008-0603-8.

"Down Syndrome" (n.d.) Retrieved from: https://www.mayoclinic.org/diseases-conditions/down-syndrome/diagnosis-treatment/drc-20355983

Ferré C, Callaghan W, Olson C, Sharma A, Barfield W. Effects of Maternal Age and Age-Specific Preterm Birth Rates on Overall Preterm Birth Rates — United States, 2007 and 2014. MMWR Morb Mortal Wkly Rep 2016;65:1181–1184. DOI: http://dx.doi.org/10.15585/mmwr.mm6543a1external icon.

Philip, A. The Evolution of Neonatology. Pediatr Res 58, 799–815 (2005). https://doi.org/10.1203/01.PDR.0000151693.46655.66

Pregnancy Over Age 30. (n.d.). Retrieved from https://www.stanfordchildrens.org/en/topic/default?id=pregnancy-over-age-30-90-P02481

Quinones, J. & Lajka, A. (2017) "'What kind of society do you want to live in?': Inside the country where Down syndrome is disappearing." Retrieved from: https://www.cbsnews.com/news/down-syndrome-iceland/

"Risks of Pregnancy Over Age 30." (n.d.) Retrieved from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=90&ContentID=P02481