From the Memory Alpha page on 2x04, Elogium - the episode in which the mother, Samantha Wildman, was introduced:

Following her introduction in this episode, Ensign Samantha Wildman became a recurring character in Star Trek: Voyager. The fact that the episode was moved from the first season of the series to its second caused an implication, regarding Ensign Wildman's pregnancy, that seems much like a mistake. In the interim between the two seasons, Jeri Taylor stated, "Because UPN is withholding it and showing it at the beginning of the season, it now makes it seem that Humans have a very strange gestation period – in which this woman was apparently pregnant for seven or eight months without realizing it!" (Star Trek Monthly issue 6) Likewise, Ken Biller felt that ending the episode with Wildman being pregnant was especially one of the episode's aspects that, due to the timing of the installment's broadcast, seemed odd. (Cinefantastique, Vol. 28, No. 4/5, p. 79) Years later, in the sixth season episode "Fury", the writing staff would finally explain Wildman's long pregnancy as having been a consequence of the baby's half-Ktarian genes.

6x23, Fury, involves time-travel. Around halfway through this episode, Janeway and the Doctor have this quick exchange:

Doctor: She planned on telling you herself.

Janeway: Boy or girl?

Doctor: Female. Half Ktarian, as a matter of fact, which should nearly double the infant's gestation period. How did you know?

So we're looking at just short of 18 months - a year and a half. Based on how stardates work, that's somewhere around 1500 "units" of stardate.

From the episode stardates for Voyager, the series started on Stardate 48315.6, while the episode in question, Deadlock, took place on 49548.7 - a difference of 1233.1 units, making the 18-month half-Ktarian pregnancy fit the time frame pretty well.

From the Memory Alpha page on 2x04, Elogium - the episode in which the mother, Samantha Wildman, was introduced:

Following her introduction in this episode, Ensign Samantha Wildman became a recurring character in Star Trek: Voyager. The fact that the episode was moved from the first season of the series to its second caused an implication, regarding Ensign Wildman's pregnancy, that seems much like a mistake. In the interim between the two seasons, Jeri Taylor stated, "Because UPN is withholding it and showing it at the beginning of the season, it now makes it seem that Humans have a very strange gestation period – in which this woman was apparently pregnant for seven or eight months without realizing it!" (Star Trek Monthly issue 6) Likewise, Ken Biller felt that ending the episode with Wildman being pregnant was especially one of the episode's aspects that, due to the timing of the installment's broadcast, seemed odd. (Cinefantastique, Vol. 28, No. 4/5, p. 79) Years later, in the sixth season episode "Fury", the writing staff would finally explain Wildman's long pregnancy as having been a consequence of the baby's half-Ktarian genes.

6x23, Fury, involves time-travel. Around halfway through this episode, Janeway and the Doctor have this quick exchange:

Doctor: She planned on telling you herself.

Janeway: Boy or girl?

Doctor: Female. Half Ktarian, as a matter of fact, which should nearly double the infant's gestation period. How did you know?

So we're looking at just short of 18 months - a year and a half. Based on how stardates work, that's somewhere around 1500 "units" of stardate.

From the episode stardates for Voyager, the series started on Stardate 48315.6, while the episode in question, Deadlock, took place on 49548.7 - a difference of 1233.1 units, making the 18-month half-Ktarian pregnancy fit the time frame pretty well.