FertilityCare Practitioners conduct Pregnancy Evaluations to provide quality control for the Creighton Model System, to provide resources and education to a couple, and to accurately date a woman’s pregnancy. A woman can schedule her pregnancy evaluation as soon as she learns she is pregnant; the evaluation is as accurate in dating a pregnancy as an early ultrasound, which usually is done around 7 weeks. There is no charge for a pregnancy evaluation.
Dating the pregnancy and determining the due date of the baby is fun to do—and couples are happy to know an accurate due date. Most important, having an accurately dated pregnancy is crucial to ensuring that mother and baby receive the best care.
Traditionally, a pregnancy is dated based on the first day of the last menstrual period (LMP). This method of dating assumes that the woman has 28 day cycles and that she ovulated on cycle day 14. With these assumptions, the due date given to the woman is actually 2 weeks LATER than the actual fetal age.
For example, if on October 1st a pregnant woman told her doctor that her last period began on September1st, the doctor would tell her that she was 4 weeks and two days pregnant. This is known as dating the “Gestational Age” of the pregnancy; it assumes the woman conceived exactly fourteen days after her last period began. The actual “Fetal Age,” however, may be very different.
When we look at a woman’s menstrual cycle, there are two phases that are relevant: the pre-ovulatory phase, and the post ovulatory phase. The pre-ovulatory phase is highly variable from month to month and may be short or long; the post ovulatory phase is stable in length. This means that the first day of a woman’s last period has absolutely no bearing on the time of ovulation during her conception cycle. So, how does assuming that all women ovulate on day 14 effect a woman and her unborn baby?
For a first example, let’s assume a woman had a short pre-ovulatory phase in the cycle in which she conceived and that ovulation occured not on day 14 but on day nine. Her baby is actually five days older than the date that would be given to her based on her last menstrual period. Throughout her entire pregnancy, she may be told that her baby is large or that her abdomen is measuring “big” beause the due date given to her is five days later than it should be. Depending on her medical and obstetrical history, she may be encouraged to have labor induced or to have a cesarean section because her baby is “measuring large for its gestational age.”
More concerning is if this same woman should carry past her due date. (Physicians usually allow a woman to carry one to two weeks past her due date at which time labor is induced or a cesarean section is performed. This is done because the placenta which supplies the baby with oxygen and nutrition can fail if a pregnancy carries on too long. Post-term babies are at higher risk for stillbirth, stress during delivery and meconium aspiration. Also, post-term babies tend to be larger, which can pose a difficulty for vaginal delivery.) But in our example, if this woman is allowed to carry to 42 weeks according to her doctor’s dating, the fetal age would actually be 42 weeks PLUS five days. Accurate dating is information that can change and improve the care for a woman and her baby!
Let’s look at a second example: we’ll assume that a woman experienced a long pre-peak phase and ovulated on day 21 of her cycle. At her first pregnancy visit, the doctor will think she is one week farther along than she really is. Her initial blood work—which because of inaccurate dating will be drawn too early—may be concerning because the hormone levels in her blood will be lower than expected. When the first ultrasound is done, her baby will also be measuring “smaller than expected.” This can lead to undue concern of miscarriage or complications.
When this same woman comes close to term she may be offered a repeat cesarean section if she had one previously, but it will be offered to her one week BEFORE her baby is actually full term. If she carries post-dates, her doctor may recommend induction or cesarean, not realizing that her baby is not really post dates at that time but is in fact just at term. Incorrect dating of the pregnancy can have a substantial effect on the prenatal care a woman receives!
Pregnancy evaluations are as accurate as early ultrasounds in determining the actual age of a pregnancy. Since Creighton Pregnancy Evaluations are based on ovulation and conception, not on the LMP, FertilityCare Practitioners are able to provide a couple with the most accurate information regarding their baby’s due date!