He has a long-standing interest in early placental development and function, and in particular how this is influenced by the prevailing oxygen concentration. In collaboration with Eric Jauniaux, he showed the importance of the uterine secretions in supporting development of the human embryo during the first three months of pregnancy before the maternal circulation to the placenta is fully established. Most recently, he has been involved in the derivation of both endometrial and trophoblast organoids, allowing the maternal-fetal interactions during early pregnancy to be investigated in a systematic fashion.

His research has been acknowledged by the award of several international prizes, including the FEDERA award from the Dutch Federation of Medical Scientific Societies, the Anne McLaren Distinguished Scientist Award from the Society for Reproduction and Fertility, and the Joan Hunt Senior Award in Placentology from the International Federation of Placenta Associations. He was elected a Fellow of the UK Academy of Medical Sciences in 2011, and of the Royal Society in 2022. He has published over 250 peer-reviewed articles, authored and edited 4 books, and written over 30 book chapters. He has an H-score of 97 (Google scholar).