Second third better

Starting at 13 weeks of gestation the second trimester is greeted with relief by most women. The fatigue and nausea that often accompany the first trimester of pregnancy will usually be resolving. By the end of the second trimester most women will feel their baby move. Early movements feel like "flutters" or like gas moving around in the abdomen. Early in the second trimester parents are offered and have to decide if they want tests for certain types of birth defects.

Between 15 and 20 weeks of gestation all women are offered the "triple screen" test. This test, done on the mother’s blood, measures levels of three different hormones (estriol, HCG, and AFP). The triple screen test is designed to identify women who are at a higher risk for carrying a fetus with a neural tube defect (spina bifida or anencephaly) or Down’s syndrome. The test detects approximately 60% of all Down’s syndrome cases. If the test shows an increased risk of either Down’s syndrome or a neural tube defect further testing will be discussed. A targeted ultrasound of the fetus, sometimes called a level 2 ultrasound, is usually the next step. Ultrasound findings may increase or decrease the risk of a fetus having Down’s syndrome. Targeted ultrasound is also very good at detecting or excluding neural tube defects. An amniocentesis may be discussed with you and recommended especially with an abnormal ultrasound or triple screen result. This involves inserting a thin needle into the uterus and removing a small amount of amniotic fluid. The fluid contains cells that are grown in a laboratory and the actual chromosomes are analyzed. Any chromosomal abnormalities, such as Down’s syndrome, will be detected by amniocentesis. Although amniocentesis is a fairly safe procedure it is associated with a small risk of miscarriage.

When deciding whether or not to proceed with the triple screen test it is important to remember that it is not a test that gives a final answer as to whether the fetus has any problems. Rather, it is a test that indicates if there is an increased risk of having a baby with a chromosomal abnormality or neural tube defect. For example in screening for chromosomal abnormalities the test is considered abnormal if the risk of having an affected fetus is greater than 1 in 250.

Women who will be 35 or older at the time of delivery are always offered the options of a targeted ultrasound and amniocentesis as their risk of having a baby with a chromosomal problem is 1 in 250 based on age alone. The risk of chromosomal abnormalities increases with maternal age reaching 1 in 50 by age 41. The risk of neural tube defects does not increase with age, however a personal or family history of this problem may prompt a targeted ultrasound. All women should consume a folic acid supplement (400ug) prior to becoming pregnant to decrease their chances of having a baby with a neural tube defect.

Most Obstetricians and Midwives will offer all their patients an ultrasound during the second trimester to look at the developing fetus and make sure there are no major birth defects. This also allows the parents to actually see their baby.

Interpretation of the triple screen test and deciding whether to have further testing can be confusing to many parents. Make sure you discuss any concerns or questions with your obstetrician.