How does the human body ensure that another pregnancy does not occur during embryonic and fetal development?

 $\frac{\frac{y=\frac{f\left(x\right)}{ }}{ }}{y=\frac{g\left(x\right)}{ }}$y=ƒ (x)  y=g(x)   

if 20mL of 1.0mol/L is to be used in this experiment and it is the limiting reagent what is the minimum volume of 1.0mol/L H2SO4 is requires to ensure H2SO4 is the excess reagent?

What is the vertical translation is applied to y=x squared if the transformation graph passes through point (4,19)?

A dynamic equilibrium will be established any time a reaction is reversed. True or false

The above image has hypothalamus-> B->D->F going up and then across. Then it is showing an arrow from the hypothalamus going down and then across to C->E->smooth muslce contractions.

Match the letters from the feedback loop diagram above with their descriptions given below. 

Which of the following rows correctly identifies the stage in development and the embryonic age most sensitive to teratogens, respectively? Select One: a). Stage: fetus, Embryonic age: 9 to 16 weeks, b). Stage: embryo Embryonic 6 to 12 weeks. c). Stage: fetus, Embryonic age 9 o 40 weeks d). Stage: embryo, Embryonic age: o to 9 weeks. 

I think its b teratogens happen during the first trimester and that happens in the embryoic development. but im not sure 

Which of the following rows correctly completes the following sentence?

______A_____ occurs during fetal development when an embryo is not exposed to adequate levels of ____B___ _______ during neurulation.

Select one: a). A: Microcephaly B: Zika virus. b). A:Anencephaly B:Folic acid. c).A:Spina bifida B: Vitamin B12. d). A:Malformation of the limbs B:Thalidomide. I think it's c but im not sure 

Stages in Fetal development: 

1. First trimester

2. second trimester 

3. third trimester

Match four of the fetal developments listed below with the appropriate trimester numbered above. 

 my asnwer for this is 2,3,3,1. is this correct?  Please let me know, whenever you get a chance to. Thank you :)