Let $X$ be a connected smooth complex algebraic variety and $Z=\bigcup\_{i=1}^r Z\_i$ be a union of smooth connected hypersurfaces, satisfying that each two intersect transversally. Assume for simplicity that $Z$ is connected and choose a point $x\in X\setminus Z$. As $Z$ has real codimension $2$, it is known that the map $\Phi:\pi\_1(X\setminus Z,x)\rightarrow \pi\_1(X,x)$ is a surjection. I am looking for a description of the kernel of this map.


I believe that this kernel should be the normalizer in $\pi\_1(X\setminus Z,x)$ of the subgroup generated by homotopy classes of loops $\tau\_i$ such that each $\tau\_i$ circles once around $Z\_i$. This is, for example, the case when $X=\mathbb{C}^n$ and $Z$ is the union of complex hyperplanes. See, for instance, [The fundamental group of the complement of a union of complex hyperplanes](https://link.springer.com/article/10.1007/BF01389187).


I have made some attempts at this, but haven't been successful thus far. My latest attempt goes as follows: Assume that $Z$ is a smooth connected hypersurface and take
a tubular neighborhood $Z\subset U\subset X$ (which we assume to contain $x$). Applying Seifert-van Kampen to the cover $X\setminus Z$ and $U$, we have an isomorphism:


$$(\pi\_1(X\setminus Z,x)\* \pi\_1(U,x))/N(\pi\_1(U\setminus Z,x)\rightarrow \pi\_1(X,x)$$.


As before, the map $\pi\_1(U\setminus Z,x)\rightarrow \pi\_1(U,x)$ is surjective. Hence, all elements coming from $\pi\_1(U,x))$ are trivial inside the amalgamated product. My feeling is that $U\setminus Z$ should deformation retract to a spherical bundle. For example, if $U$ is trivial then $U\setminus Z$ is homotopy equivalent to $Z\times \mathbb{S}^1$, and the loop corresponding to $(id, 1)\in \pi\_1(Z\times \mathbb{S}^1,x))\simeq \pi\_1(Z,x)\times \mathbb{Z}$ generates the kernel of $\Phi$. I would very much appreciate any help regarding this matter.



Presentation of the fundamental group of a complex variety
I found an affirmative answer to this question on [Complex reflection groups, braid groups, and Hecke algebras](https://www.degruyter.com/document/doi/10.1515/crll.1998.064/html?lang=en). The proof is in Appendix A1, specifically on page 181.


