Table 1.

Estimated critical and sensitive windows for specific human reproduction and development

Sensitive Window	Estimated Duration of Sensitive Window
Males
Steroidogenesis and spermatogenesis	72 days
Females
Folliculogenesis (selection dominant follicle)	4 months
Menstrual and ovarian cycles	29 days
Ovulation (post surge in luteinizing hormone)	24–36 hours
Fertilization	3–4 hours
Implantation	4–6 days
Early Conceptus
Zygote	1 day
2-cell stage	1–2 days
4-cell stage	1–2 days
Morula	1–2 days
Blastocyst (formation and implantation)	1–2 days
Pregnancy (post-conception)	266 days 280 days (LMP)
Embryo (post-conception)	56 days
Fetus (post-conception)	30 weeks

NOTE: All times are estimated and vary across individuals and data source. LMP, last menstrual period dating.