Brief Answer: Second Detailed Answer: Hi, Thanks for your query. From the timing you describe it sounds like number two is your man for bothering this pregnancy. In addition the earlier and ultrasound was carried out in the pregnancy the more likely it is to be precise. A six-week 6 day ultrasound on 7/31 puts you conceiving between late XXXXXXX and early July, six weeks six days from first day of the last menses midway between the dates you give for #2. sperm can conceive up to three days after ejaculation. it's number two by the numbers. If you want 100% certainty you need to do a paternity test after the baby is born. DNA never lies. Regards,

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Brief Answer: Due date once established early is fixed. Detailed Answer: The earlier a due date is established the more accurate it is. Events that occur later in pregnancy such as a small for dateis baby or large for dates baby will have other explanations not that the due date was wrong. The numbers you describe are perfectly accurate for 37-38 weeks. The shortening of the cervix is also normal in the last weeks of pregnancy. A term pregnancy is anywhere between 38 and 42 weeks. It does not mean that the due date has changed. 'Any day' is a pretty vague term. My guess is you will be closer to 39 to 40 weeks as are most women. All pregnancies start out the same which is why that early ultrasound matching your dates is so accurate. The individual variation of late pregnancy does not change your last menstrual period, early ultrasound or probably date of conception. During the years that I practiced obstetrics and delivered thousands of babies I never changed a due date established by such a method.

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