New Zealand Black Caps captain Kane Williamson's involvement in the second cricket test against West Indies in Wellington is in doubt after he left the squad to be with his pregnant wife.

The Black Caps said in a statement that Williamson had flown to Tauranga to attend a midwife's appointment with wife Sarah, who is expecting their first child.

Coach Gary Stead will provide an update at 12.30pm as to whether Williamson will play the test starting on Friday.

Devon Conway has been summoned to the squad as cover, with the Black Caps saying at this stage Williamson was still available for the match.

Williamson said of impending fatherhood during the first test, when asked if he would miss national duties: 'It's sort of wait-and-see. It's a very exciting time in anybody's life and certainly in mine.

'We're just going to cross that bridge when we can and see how things unfold, but very difficult to pre-plan.”

If Williamson was to be ruled out, Will Young would replace him as batting cover ahead of Conway in the queue.

Wicketkeeper BJ Watling is expected to be passed fit after missing the innings and 134 run victory in Hamilton, meaning Tom Blundell hands over the gloves and returns to the top of the order.

Either Tim Southee or Tom Latham would captain the side in Williamson's absence.

-Stuff.