age/pregnancy

[johnlinda]

I am a 36 yo caucasian.  I have a 19 year old son(birth weight 10 lbs 5 oz.) and a 11 month old son (birth weight 8 lbs 4 oz.).  The 1st was born vaginally and the second elective c-section.  Anyway, I am considering trying to get pregnant again.  Am I too old? Are my chances of birth defects much higher at this age.  If I do get pregnant what are my options for testing to help ease my mind.  What tests should I do before trying to conceive and what tests can be done after conception?  I am a CF carrier, my husband is not.  Also, please note that during my second pregnancy I went to Birmingham, Alabama to have an amniocentesis done at 17 weeks and they were unable to obtain fluid after 3 sticks ( the doctor said my uterus was like a partially inflated balloon at the time.  Anyway, both pregnancies were completely normal.  Please advise and thanks for your time.

[Lisa Kessler, MS, CGC]

Thank you for questions.  I hope that the following information helps in your decision making.  Most pregnancies end with the birth of a healthy baby. About 3/100 babies is born with a birth defect. Many factors affect this chance (previous personal and family history, maternal health, maternal exposures, ethnicity, and of course maternal age).   Maternal age increase the risk for only one kind of birth defect: chromosome abnormalities.  For a woman who is 36 or 37 when she delivers, her risks are in the range of less than 1% to have a child with a chromosome abnormality .  In other words, there is a greater than 99% chance to have a baby without a chromosome abnormality for a woman ages 36 or 37 years at the time of delivery.  

Everyone perceives risk numbers differently, and you have many options to consider regarding prenatal testing.  There are prenatal screening tests that provide risk estimates for specific chromosome abnormalities, but do not diagnose chromosome abnormalities or provide a “yes or no” answer.  For example, first trimester screening is an early screening option for a few of the most common chromosome abnormalities seen at birth.   This involves a blood test and an early ultrasound performed at 9.5-13.9 weeks.  In addition to first trimester screening is quad screening which is done later in pregnancy (15-20 weeks), involves just a blood test, and screens for more disorders.  

Diagnostic testing options include CVS and amniocentesis.  These tests diagnose chromosome abnormalities and other very specific genetic tests for at-risk couples.  Generally, CVS is performed at 10-13 weeks gestational age, and has a risk for miscarriage that varies from about 1 in 100 to 1 in 300.  Amniocentesis is generally performed from 15 to greater than 20 weeks, and risks for miscarriage range from 1 in 200 to 1 in 500.   About your own amnio experience, there is a small risk with every amnio that there will be a failure of the procedure for many reasons.  I would recommend discussing this with your doctor and with your amnio practitioner.

Regarding CF-   Since you and your partner have already had CF screening, and leaned that you are carrier and your partner is not, then your risk to have a child with CF is greatly lowered but not to zero.    

Prenatal testing for birth defects is complex and quite personal. Some women choose to have no testing for birth defects during pregnancy because they are not interested in having information about birth defects until their baby is born. Women have many options and should think all of them through considering the medical facts and their own personal/family values.   You may benefit from discussing your options with a genetic counselor.  You can locate a genetic counselor through the NSGC website.