Methods pregnancy dating sibdatingru
Determining the Date of Conception 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.
303, February 2014 Society of Obstetricians and Gynaecologists of Canada.
Multifetal gestations: twin, triplet, and higher-order multifetal pregnancies.
The due date may be estimated by adding 280 days ( 9 months and 7 days) to the first day of the last menstrual period (LMP). The accuracy of the EDD derived by this method depends on accurate recall by the mother, assumes regular 28 day cycles, and that ovulation and conception occurs on day 14 of the cycle.
Chorionic gonadotropin secretion by human embryos in vitro.
The American College of Obstetricians and Gynecologists.
Berghella V, et al., Does transvaginal sonographic measurement of cervical length before 14 weeks predict preterm delivery in high-risk pregnancies?
Page JM, The risk of stillbirth and infant death by each additional week of expectant management in twin pregnancies.
Risk of late-preterm stillbirth and neonatal morbidity for monochorionic and dichorionic twins.