Table 1.

Determination of the project estimated date of delivery (EDD)/gestational age

Circumstance of pregnancy dating before visit	Final project EDD based on
Unsure LMP	CRL measured (cm) and put into Hadlock formula35: $\begin{array}{l}exp[1.684969+(0.315646\ast \text{CRL})-(0.049306\ast \text{CRL}\ast \text{CRL})+\\ (0.004057\ast \text{CRL}\ast \text{CRL}\ast \text{CRL})-(0.000120456\ast \text{CRL}\ast \text{CRL}\ast \text{CRL}\ast \text{CRL})\end{array}$
	Project EDD = Project ultrasound date + (280 – ultrasound estimated gestational age in days
“Sure” LMP	CRL measured confirming LMP or changing the EDD. Project EDD = LMP +28 days if confirmed. If not, Project EDD = ultrasound EDD Cutoffs utilized:
	EGA at 1st ultrasound by LMP	Project US agreement with LMP
	<70 weeks	±3 days
	70 to 75 weeks	±4 days
	80 to 106 weeks	±5 days
	110 to 126 weeks	±6 days
	130 weeks or more	±7 days
Pregnancy conceived using artificial insemination	Project EDD = Date of insemination + 266 days
Pregnancy conceived by in-vitro fertilization	For a “3-day” fresh/frozen embryo replacement date: Project EDD = embryo replacement date + 263 days
	For a “5-day” fresh/frozen replacement date: Project EDD = embryo replacement date + 261 days

LMP= last normal menstrual period; CRL = crown rump length measured by 1^st trimester ultrasound; EDD = estimated due date; US = ultrasound