1. Mid-pregnancy, perinatal, and neonatal reproductive endocrinology: a prospective cohort study in twins and singleton control subjects 
Esther A.M. Kuijper, M.D., Ph.D., Jos W.R. Twisk, Ph.D., Ted Korsen, Mirte R. Caanen, M.D., Mark M. Kushnir, Ph.D., Alan L. Rockwood, Ph.D., A. Wayne Meikle, M.D., Peter G. Hompes, M.D., Ph.D., Jan M. Wit, M.D., Ph.D., Cornelis B. Lambalk, M.D., Ph.D. 
Fertility and Sterility 
Volume 104, Issue 6, Pages e9 (December 2015)
DOI: /j.fertnstert
Copyright © 2015 American Society for Reproductive Medicine Terms and Conditions

2. Figure 1
The number of mothers pregnant with (A) twins or (B) singletons and their neonates at different time points, according to zygosity, sex, and mode of conception. ART = assisted reproduction; DZ = dizygotic; GA = gestational age; MZ = monozygotic; NC = natural conception; ? = mode of conception unreported; ∗cord blood from only one child of the twin.
Fertility and Sterility  , e9DOI: ( /j.fertnstert )
Copyright © 2015 American Society for Reproductive Medicine Terms and Conditions

3. Figure 2
Median estrogen (E1, E2, and E3) and progesterone (P) concentrations in singletons and twins at mid-gestation and time of delivery in maternal serum and umbilical cord blood. ∗Significantly different concentrations between twins and singletons.
Fertility and Sterility  , e9DOI: ( /j.fertnstert )
Copyright © 2015 American Society for Reproductive Medicine Terms and Conditions

4. Supplemental Figure 1
The range of gestational ages at birth according to zygosity. DZ = dizygotic; MZ = monozygotic.
Fertility and Sterility  , e9DOI: ( /j.fertnstert )
Copyright © 2015 American Society for Reproductive Medicine Terms and Conditions