conception occurs during ovulation.We should at least have some idea - when you had ovulated.If you measured the rectal temperature, the day of ovulation you know for sure.If the temperature is not measured - guided only about the dates.
from the expected date of the next menstruation subtract 14 days.Note, this method is only suitable for the regular cycle.And the cycle can affect different factors, ranging from stress and ending with taking drugs, so the method is very approximate.Knowing the exact
date of ovulation, you will know the day of conception.
in early pregnancy (6-7 weeks) ultrasound is considered very accurate, error total is 2-3 days.In this period the embryo grows in proportion, and its dimensions in all women with the same period will be the same.In the later stages of the fetus is developing in different women individually and depends on many factors: the weight of the mothers and fathers, of nationality, and so on. D. Does it mean that at a later date, conceived in the same time, kids canhave very different sizes.And to establish the exact date using ultrasound fail.
In the first stirring toddler can determine the duration of pregnancy, but not very accurate.Since all women, it can be individually.On average, the perturbations must be felt at 18-20 weeks, then there exists an error of 2 weeks.But some women (lean physique or multiparous) may feel the baby move at 16 weeks, and thus the error can be much larger.
Determine Maturity your pregnancy in several ways, but it would be better if we use the totality of all of these methods.If the data are very different, it is best to focus on more precise - an early ultrasound and ovulation date.