Objectives: There are no international standards for relating fetal crown-rump length CRL to gestational age GA , and most existing charts have considerable methodological limitations. GA was calculated on the basis of a certain last menstrual period, regular menstrual cycle and lack of hormonal medication or breastfeeding in the preceding 2 months. CRL was measured using strict protocols and quality-control measures. All women were followed up throughout pregnancy until delivery and hospital discharge.
Pregnancy Due Date Calculator
Metrics details. Conventionally, the pregnancy duration is accepted to be — days. Fetuses determined by ultrasound biometry to be small in early pregnancy, have an increased risk of premature birth. We speculate that the higher rate of preterm delivery in such small fetuses represents a pathological outcome not applicable to physiological pregnancies. Here we test the hypothesis that in low-risk pregnancies fetal growth expressed by fetal size in the second trimester is itself a determinant for pregnancy duration with the slower growing fetuses having a longer pregnancy. We analysed duration of gestation data for women who had a spontaneous delivery having previously been recruited to a cross-sectional study of low-risk pregnancies. All had a regular menses and a known date of their last menstrual period LMP.
Lecture 10: Fetal biometry: dating, assessing size and estimating fetal weight
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Because the human egg is capable of fertilization for only 12 to 24 hours after ovulation the date of ovulation may be taken as being the date of conception. However, ultrasound determination of the date of ovulation has the same imprecision as does the ultrasound estimate of the gestational age and, therefore, a precise date of conception cannot usually be determined as with in vitro fertilization. In addition, although a woman is most likely to become pregnant if she has sex on the day of ovulation conception may also occur from live sperm still in her reproductive tract on the day of ovulation if she had sex for up to five days before ovulation [26,27].